Facts and figures.

• How does lifestyle affect my breast cancer risk?

  Q1. Is being overweight or obese a risk factor for breast cancer?

  Being overweight or obese after menopause significantly increases the risk of breast cancer. A UK study found that postmenopausal women who were obese had around a 30% higher risk of developing breast cancer compared to those of a healthy weight.

  Excess weight is also a risk factor for breast cancer in men.

  Q2. Does being overweight or obese increase the risk of breast cancer in premenopausal women?

  Despite increasing the risk of breast cancer in postmenopausal women, weight gain and being overweight or obese does not appear to increase the risk of breast cancer in premenopausal women.

  However, young women should not intentionally gain weight to reduce their breast cancer risk. Some studies suggest that obese premenopausal women who get breast cancer tend to have more aggressive subtypes (e.g. triple-negative breast cancer). Weight gain throughout adulthood increases your risk of developing breast cancer after menopause. Additionally, weight gain and excess weight are also associated with a variety of other health risks, including cardiovascular diseases, diabetes, and other cancers.

  The reasons that excess weight before menopause does not appear to increase the risk of breast cancer are not fully understood, although they may relate to oestrogen production, which is mainly produced by the ovaries in premenopausal women and by fat tissue in women following menopause. In premenopausal women, excess fat tissue affects the functioning of the ovaries, resulting in a reduction in menstrual cycles and, as a result, reduced exposure to sex hormones, including oestrogen. After menopause, excess fat tissue increases levels of circulating oestrogens, which increases your breast cancer risk.

  It should also be noted that many endocrine disrupting chemicals (EDCs) are fat-soluble and can be stored in fat cells. Certain EDCs may increase breast cancer risk. Finally, many health risks are associated with being overweight or obese, so it is important for women to maintain a healthy weight throughout life.

  Q3. Is there a link between eating processed meat and breast cancer?

  There is convincing evidence that increased consumption of processed meats, such as bacon and salami, slightly increases breast cancer risk.

  Q4. Can a healthy diet help to prevent breast cancer?

  A healthy and balanced diet can help reduce your risk of breast cancer.

  While no single food can prevent breast cancer, certain dietary habits are linked to lower risk, including:

  • Eating plenty of fruit and vegetables, especially non-starchy vegetables like broccoli, cauliflower, or aubergines, and those rich in carotenoids such as, sweet potato, tomatoes and carrots).
  • Including foods rich in vitamin D, like oily fish (e.g. salmon) or mushrooms.
  • Eating unsweetened dairy products or dairy alternatives, which contain calcium and may contain beneficial bacteria.
  • Limiting or avoiding red meat and processed meats.
  • Low or, ideally no alcohol.
  • Aiming for at least 30g of fibre a day. It is found naturally in plant foods like whole grains, beans, nuts, fruit and vegetables
  • Not eating more than is needed so that you can maintain a healthy weight for your height

  For further information, please visit our diet factsheet.

  Q5. Does drinking alcohol increase my breast cancer risk?

  Drinking alcohol increases the risk of breast cancer in women, and heavy alcohol consumption increases the risk in men.

  For women, the more alcohol is consumed, the greater the risk, with no safe lower limit.

  Q6. What is the ideal diet to decrease my risk of breast cancer?

  There is no ideal diet for breast cancer prevention; rather, it is more important to pay attention to the proportions of different food groups you consume. Many diets can be healthy and help reduce your risk, including the Mediterranean diet and balanced vegetarian diets.

  These diets typically focus on whole, minimally processed foods, emphasising plenty of fruits, vegetables, and high-fibre foods, while limiting or avoiding red and processed meats.

  Q7. Does eating a vegan or vegetarian diet decrease breast cancer risk?

  There is insufficient evidence to be certain that vegetarians or vegans have a lower risk of developing breast cancer. However, many components that make up a healthy vegan or vegetarian diet have been shown to reduce breast cancer risk. For example, eating plenty of fruits and non-starchy vegetables,  choosing plant-based protein sources like tofu, nuts, and legumes, and including calcium-rich foods like dairy or fortified dairy alternatives.

  A well-balanced vegetarian or vegan diet can also support maintaining a healthy weight or weight loss for those who need to, which is important for breast cancer prevention. These diets are often rich in fibre and tend to be lower in calories, total fat and saturated fat compared to diets high in animal products.

  However, the benefits of vegetarian or vegan diets largely depend on the types of foods you eat and your overall dietary habits. While many plant-based products are a good source of fibre and protein, some processed vegetarian/vegan foods may also contain additives, stabilisers and enhancers to mimic the taste and texture of meat, which can make them a less healthy option. We recommend looking over ingredient lists to help you make an informed choice.

  Q8. Does eating organic food decrease my risk of getting breast cancer?

  Current research investigating the effects of organic food on breast cancer risk has so far yielded mixed results. Some studies have shown that a diet rich in organic food may reduce breast cancer risk, especially post-menopause, while a large UK study found no link between organic food and reduced risk.

  However, eating organic food can lower your exposure to pesticides, some of which may increase breast cancer risk. For example, the insecticide malathion and the herbicide glyphosate may increase breast cancer risk by disrupting hormones, especially oestrogen.

  To help reduce pesticide exposure, the Dirty Dozen is a list of conventionally grown fruits and vegetables with the highest pesticide residues. It is based on PAN UK’s analysis of the UK government’s pesticide residue testing programme.

  Q9. Does drinking cow’s milk increase breast cancer risk?

  There is not enough evidence to conclude that drinking cow’s milk increases or decreases breast cancer risk. Several meta-analyses suggest that a diet high in milk does not affect breast cancer risk, while a few meta-analyses suggest dairy products may reduce pre-menopausal breast cancer risk and have no effect on risk for women after menopause. However, findings from observational studies are varied – some report that a diet high in cow’s milk increases risk, others report the opposite, and many others show no association.

  Dairy products are a source of calcium and vitamin D, both of which may help reduce the risk of breast cancer.

  Concerns about cow’s milk stem from the fact that it typically comes from pregnant cows and contains high levels of bovine hormones, including bovine oestrogen. These hormones can increase levels of human insulin growth factor 1 (IGF-1), and higher levels of IGF-1 in women have been associated with a slight increase in breast cancer risk.

  More research is needed to understand the impact of drinking cow’s milk on breast cancer risk.

  Q10. Can vitamin D supplements reduce my breast cancer risk?

  While low levels of vitamin D have been linked to an increased breast cancer risk, most studies have not shown that taking vitamin D supplements reduces breast cancer risk. The reasons for this are unclear, and further research is needed. However, supplements can help restore circulating vitamin D levels to a healthy state and are recommended for people unable to get enough through sunshine and diet.

  Q11. Does consuming too much sugar increase breast cancer risk?

  There is currently not enough evidence to conclude that there is a link between a high-sugar diet and an increased risk of breast cancer, although some studies have suggested a possible connection.

  However,  excessive sugar intake can promote weight gain, often without the added benefit of vitamins and minerals (so-called “empty calories”) and being overweight or obese is a known risk factor for breast cancer in men and postmenopausal women.

  Further research is needed to understand whether there is a link between sugar and breast cancer risk.

  Q12. Does consuming products containing artificial sweeteners increase breast cancer risk?

  There is currently no evidence to suggest a strong link between artificial sweeteners and breast cancer risk.

  A  2022 study identified a link between a higher intake of certain artificial sweeteners (especially aspartame) and breast cancer risk.  In July 2023, the International Agency for Research on Cancer classed the artificial sweetener aspartame as ‘possibly carcinogenic’ (group 2B). This means of the research it has reviewed; it has found limited evidence that aspartame can cause cancer.  However, it is recommended to limit the consumption of food and drinks containing artificial sweeteners.

  However, a recent study in 2025 looking at breast cancer risk in the Nurses' Health Study (NHS) and NHS II found that aspartame consumption did not increase breast cancer risk.

  Therefore, the relationship between artificial sweeteners and breast cancer remains unclear, with contradictory results, and more research is required to confirm whether there is an association.

  Q13. Does eating soy products increase breast cancer risk?

  Eating soy products does not increase breast cancer risk even though soy contains phytoestrogens. In fact, several recent studies have suggested that a diet rich in soy-based foods, such as tofu, may offer a protective effect. However, more research is needed to confirm this finding.

  Q14. Does physical activity affect my risk of breast cancer?

  Physical activity helps to lower breast cancer risk. It also helps prevent recurrence and mortality following a breast cancer diagnosis.

  Studies suggest being physically active can reduce your risk of breast cancer by around 20%. Any type of additional physical activity is beneficial; the more, the better. We recommend, as a minimum, following the World Health Organisation’s (WHO) guidelines of at least 150 minutes of moderate, or 75 minutes of vigorous, physical activity weekly.

  Q15: Does smoking increase breast cancer risk?

  Smoking slightly increases breast cancer risk. Most (but not all) studies and meta-analyses conclude there is a modest increase in breast cancer risk for those who smoke, with the risk of breast cancer around 10% higher in women who smoke compared to those who never have. It is currently estimated that smoking tobacco causes around 4% of cancers in the UK.

  Q16: Does vaping increase breast cancer risk?

  As e-cigarettes are a relatively new product, there is currently limited evidence on the link between vaping and breast cancer. While e-cigarettes do not contain tobacco - which contains several harmful chemicals and substances - they can contain some chemicals at lower levels that have previously been linked to breast cancer risk.

• How does chemicals and the environment affect my breast cancer risk?

  Q1. How might exposure to certain chemicals increase breast cancer risk?

  Some chemicals are harmful and can damage our DNA, known as carcinogens. Others may be harmful as they can interfere with our hormones; these are known as endocrine (or hormone) disrupting chemicals (EDCs). Some EDCs can mimic the actions of the natural hormone oestrogen; exposure to high levels of this hormone increases breast cancer risk. Similarly, exposure to compounds that mimic oestrogen may also increase risk.

  For further details, visit our Chemicals factsheet.

  Q2. Where are Endocrine Disrupting chemicals found?

  Endocrine Disrupting Chemicals (EDCs) are found in many everyday products such as cosmetics, kitchenware, plastic bottles, the lining of metal food cans, furniture and furnishings, electronics, toys, pesticides, waterproof clothing and food. They are also present in air, soil and water.

  They enter your body through eating, drinking, breathing and absorption through your skin.

  Q3. Why don’t other cancer charities highlight exposures to harmful chemicals (such as Endocrine Disrupting Chemicals) as breast cancer risk factors?

  Most cancer charities choose to prioritise other, more well-established risk factors for breast cancer over exposure to chemicals of concern, including endocrine disrupting chemicals (EDCs). Some charities are not yet convinced that sufficient evidence is available to demonstrate that harmful chemicals, such as EDCs that are oestrogen mimics, increase breast cancer risk. This is due to a lack of research into the effects of harmful chemicals on human health at human-relevant concentrations.

  Whilst we support the valuable work other cancer charities do, warnings from reputable scientists as well as bodies such as the United Nations Environment Programme, World Health Organisation (WHO) and the Endocrine Society suggest that chemical exposure, particularly to multiple compounds throughout life and at specific life stages does have implications for human health, including potentially increasing the risk of breast cancer.

  At Breast Cancer UK, we adopt a precautionary approach. If there is scientific evidence that a chemical has a possible link to breast cancer, we advise reducing your exposure to that chemical and lobbying for its use to be restricted or banned so that everyone is more protected.

  To find out more, visit our chemicals page in the reduce your risk section of our website

  Q4. Does drinking water from plastic bottles increase breast cancer risk?

  Some types of plastic bottles contain bisphenols (found in polycarbonate plastics; plastic recycling code 7) or phthalates (found in recycled PET, plastic recycling code 1) which may contribute to an increased risk of breast cancer. It is very unlikely that occasional exposure to such chemicals will result in breast cancer development. However, repeatedly using plastic bottles can increase our overall exposure to chemicals known as EDCs as they can leach out into the liquids they contain, especially if heated.

  EDCs can interfere with our hormones such as oestrogen and long-term exposure to these chemicals may contribute to an increased breast cancer risk.

  Q5. Do antiperspirants and deodorants increase breast cancer risk?

  There is currently not enough conclusive evidence to say that using deodorants and antiperspirants increases breast cancer risk. Most antiperspirants contain aluminium salts which can mimic the hormone oestrogen and accumulate in breast tissue. This is why some scientists believe it may increase breast cancer risk.

  Other types of deodorants contain perfume and Endocrine Disrupting Chemicals (EDCs) such as parabens;  which have been shown to mimic oestrogen and may also increase the risk of breast cancer.

  It is currently unclear how long-term use of deodorants and antiperspirants affect breast cancer risk and more research is needed in this area.

  Q6. Does using products containing lavender oil increase my risk of breast cancer?

  To our knowledge, no studies have investigated whether there is an association between lavender oil use and breast cancer risk. Some in vitro studies (experiments done on cells in a lab) have demonstrated that lavender oil has oestrogenic properties similar to some synthetic endocrine disrupting chemicals (EDCs).

  One small study found an association between the use of products containing lavender and premature breast development in young girls, which may be a risk factor for breast cancer. Regular exposure to lavender oil has also been linked to abnormal breast growth in young boys, known as prepubertal gynecomastia. However, studies are still inconclusive and more research is needed.

  Repeated use of Lavendar oil may affect the levels of the hormone oestrogen in the body, and it is noted that individuals with oestrogen receptor positive cancers (including breast cancer) need to be careful with its’ use.

  We, therefore, recommend a cautious approach to using lavender-based products, particularly if you have been diagnosed with a hormone receptor positive cancer.

  Q7. How can I tell if personal care products contain endocrine disrupting chemicals (EDCs)?

  To identify EDCs found in personal care products, we recommend using our A to Z Chemicals of Concern list which can also help identify EDCs in consumer products which may be linked to breast cancer.

  Q8. What suncreams should I avoid?

  Many suncreams contain various Endocrine Disrupting Chemicals (EDCs), which we recommend you avoid. These include parabens such as propylparaben (used as preservatives) and chemical UV filters (active ingredients), for example, homosalate, ethylhexyl salicylate and butyl methoxydibenzoylmethane.  These ingredients can interfere with hormones such as oestrogen which may increase breast cancer risk. They can also cause environmental damage.

  We recommend using a mineral-based suncream, which contains zinc oxide in its non-nano form (nano-form suncreams can be absorbed by the skin and may harm aquatic life). Spray and powder form suncreams should also be avoided due to the risk of inhalation.

  Our A-Z chemicals of concern list can help in selecting sunscreen.  However, if you do need sun protection urgently, using any suncream is better than getting sunburnt.

  Q9. Does eating food stored in plastic containers or takeaway boxes increase breast cancer risk?

  Many plastic containers and takeaway boxes, including the greaseproof linings of pizza boxes, contain Endocrine Disrupting Chemicals (EDCs) including bisphenols, phthalates and PFAS, which may, affect breast cancer risk in the long-term. 

  These chemicals can leach from containers/wrapping material into food (and the environment), leading to unintentional human exposures. The leaching process may also be accelerated under certain conditions, including high temperature (e.g., microwaving), high pH (e.g., detergents) and prolonged contact time.

  Occasional exposures to EDCs are unlikely to confer an increased breast cancer risk. However, repeated and frequent exposure to synthetic chemicals such as bisphenols, which can mimic the effects of oestrogen, may be a risk factor for breast cancer.

  In December 2024, the European Commission adopted a ban on the use of BPA and other bisphenols in food contact materials due to its potential harmful effects on human health. No such regulation has yet come into force in the UK.

  Q10. Can my child be exposed to EDCs in the womb?

  Biomonitoring studies have detected various endocrine disrupting chemicals (EDCs) in the placenta, umbilical cord serum of mothers and the urine of unborn children. Furthermore, animal studies have found that exposure to EDCs in the womb (termed ‘in utero’) may increase the risk of breast cancer during adulthood. More studies are required to assess the long-term impact of chemical exposures in utero. You can read our advice for protecting your baby’s health and for more information on how exposure to chemicals in the womb can affect breast cancer risk here.

  Q11. Does exposure to parabens affect breast cancer risk?

  Cell culture (those undertaken in a laboratory) and animal studies suggest that long-term exposure to certain parabens may increase breast cancer risk. Parabens can mimic the actions of oestrogen. Parabens may be involved in various stages of tumour formation and growth and may contribute to the spread of cancer cells to other parts of the body. At high concentrations, they promote genotoxicity (damage DNA).

  Animal studies have found that propylparaben, at levels relevant to human exposure, can induce long-term alterations to the mammary gland, which may make animals more susceptible to mammary cancer. Methylparaben may reduce the effectiveness of tamoxifen for treating breast cancer.

  Parabens have been measured in breast tissue and other body fluids in humans. However, most epidemiological studies have not demonstrated a link between parabens and breast cancer.

  You can find more information on parabens and breast cancer risk here.

  Q12. What are microplastics and can they affect breast cancer risk? 

  Microplastics are defined as plastic pieces that are less than 5mm in size, are insoluble in water and can take centuries to break down completely. Primary microplastics are intentionally made for commercial purposes, such as microbeads in cosmetic products and microfibres in clothing. Secondary microplastics result from the breakdown of larger plastics and are often found polluting land and aquatic environments. These microplastics have been detected in wildlife and in human blood, breast milk and tissues.

  There is limited evidence on the link between microplastic exposure and breast cancer risk, yet it is a significant concern for human health. Microplastics may already contain harmful chemicals, but they can also absorb other chemicals and transfer them to the surrounding environment. Many of these chemicals (including bisphenols, PFAS and phthalates) have previously been linked to an increased breast cancer risk.

  Q13. What are forever chemicals? 

  Forever chemicals are per- and polyfluorinated alkyl substances (PFAS) that do not naturally break down in the environment or in our bodies. This can lead to chemical build-up in the human body, which may promote adverse health effects. Some studies have linked some PFAS with an increased risk of breast cancer.

  PFAS compounds are found in many everyday items including food packaging and clothing to make them waterproof, furniture, some cosmetics and beauty products and non-stick cookware.

  Due to their inability to break down quickly, we can still be exposed to those PFAS that have been banned in consumer products for many years in the future.

  You can find more information on PFAS and breast cancer risk here.

  Q14. What is an ‘obesogen’? 

  An obesogen is a chemical compound that can disrupt normal fat metabolism processes and may influence or promote obesity. They may act in the body by increasing the number of fat cells or increasing the storage of existing fat cells.

  Several obesogens are also endocrine disrupting chemicals (EDCs). Many obesogenic EDCs including some bisphenols, phthalates and pesticides have previously been linked to breast cancer risk. The human breast contains a large proportion of fat, and many EDCs have been shown to accumulate in breast fat tissue, which could influence breast cancer development.

• Can reproductive factors and hormones affect my breast cancer risk?

  Q1. Is breast cancer during pregnancy common?

  Breast cancer during pregnancy, or pregnancy-associated breast cancer (PABC) is rare and is defined as breast cancer diagnosed during pregnancy or in the first postpartum year. It occurs in around 1 in every 3,000 pregnancies. Read more on pregnancy and breast cancer is here.

  Q2. How does age at the birth of a first child affect your breast cancer risk?

  Women who have their first child over the age of 30 have an increased risk of breast cancer that lasts for around 20 years.

  Although having children at a younger age lowers the long-term risk, the first pregnancy at any age increases the short-term risk of breast cancer. Women who have recently given birth have a short-term increase in breast cancer risk which peaks around five years after childbirth.

  Q3. Does breastfeeding reduce the risk of breast cancer?

  Breastfeeding lowers the risk of developing breast cancer. The longer you breastfeed, the more risk is reduced. Although mechanisms are not fully understood, breastfeeding changes breast tissue by eliminating cells with DNA damage and reduces the lifetime number of menstrual cycles, altering exposure to specific hormones which can influence breast cancer risk. You can read more about breastfeeding and breast cancer here.

  Q4. Does HRT cause breast cancer? 

  Whilst some forms of hormone replacement therapy, or HRT, are associated with an increase in breast cancer risk; the extent of the risk depends on the type of HRT and the duration of use.

  With oestrogen-only HRT, there is little to no increased risk of breast cancer. This type of HRT is usually only recommended to people who have had their uterus removed (hysterectomy).

  For combined HRT (oestrogen and progestogen), breast cancer risk increases when used over five years. Increased risk declines when the combined HRT treatment is stopped, but some risk remains if used for over ten years.

  Q5. Is it true that I’m more at risk if I don’t have children?

  Women who do not have children can be at an increased risk of breast cancer, especially some subtypes such as luminal breast cancer.

  Q6. If I’m on a contraceptive pill or another type of hormonal contraception, am I at increased breast cancer risk?

  The contraceptive pill can contain either a combination of both synthetic oestrogen and synthetic progesterone (known as progestogen) or progestogen-only. Studies have shown that taking combined oral contraceptives (oestrogen and progestogen) slightly increases breast cancer risk. The risk is no longer evident ten years after use has stopped.

  Some studies suggest contraceptive pills containing progestogen-only may not be associated with breast cancer risk, while a more recent 2023 study has shown a very slight increase. More studies are needed to confirm this.

  Other types of hormonal contraceptives include injections and hormone-releasing intrauterine systems (e.g., Mirena coil), which contain progestogen, and patches and vaginal rings, which use both oestrogen and progestogen. There are fewer studies into the risks associated with these types of contraceptives, although the risks are thought to be similar to those associated with the contraceptive pill.

  Q7. Why are high levels of oestrogen potentially harmful?

  Higher levels of circulating oestrogens are associated with an increased risk of breast cancer (this is also true for men). Oestrogen encourages certain cell types, including breast cells, to divide more often. The more a cell divides, the more likely mutations will accumulate, which may lead to breast cancer. Oestrogen also encourages the growth of oestrogen receptor-positive breast cancers.

  Q8. Do transgender women have an increased risk of breast cancer?

  Several studies have shown transgender women (those assigned male sex at birth who identify as women) who undergo hormone treatment have an increased risk of breast cancer compared to cis men (who have not undergone treatment).

  However, transgender women are still at a lower risk of breast cancer compared to cis women who have not undergone hormone treatment. Transgender women who take hormone therapy may have a higher risk of breast cancer than the cis male population but a lower risk than the cis female population.

  For more information, see our resource for transgender people.

  Q9. Do transgender men have an increased risk of breast cancer?

  A Dutch study, based on a small sample size, found that transgender men (those assigned female sex at birth who identify as men) who undergo hormone treatment are at a lower risk of breast cancer compared to cis women (who have not undergone treatment) but at a higher risk than cis men.

  Many transgender men undergo a double mastectomy (breast tissue removal), which reduces breast cancer risk. Nonetheless, everyone is susceptible to breast cancer, and not all trans men undergo mastectomies, meaning they may remain at higher risk. Further studies are needed to assess the potential risks of long-term testosterone treatment.

  For more information, see our resource for transgender people.

• How does genetics and family history affect my breast cancer risk ?

  Q1. Are there any ethnic groups in the UK more at risk of breast cancer?

  Some ethnic groups, including those with an Ashkenazi Jewish background, are more at risk than others. Some ethnic groups appear to have a lower risk. This may be due to genetics or lifestyle factors.

  Individuals with an Ashkenazi Jewish background have a much higher risk of inheriting a BRCA gene mutation compared to other members of the UK population. Inheriting BRCA mutations increases breast cancer risk considerably. Please see Section 5 Q2 for more details about BRCA genes.

  Studies have shown that some UK ethnic groups have lower breast cancer rates. Women from South Asian, Chinese, black Caribbean and black African ethnic groups have a lower incidence compared to white women. This is thought to be due to differences in known reproductive and lifestyle factors for the disease, such as having more children at a younger age; breastfeeding; lower body mass index post-menopause; lower alcohol consumption and less use of hormone replacement therapy.

  Despite a lower breast cancer incidence compared to the white population, it is also true that black Caribbean, black African, Indian and Pakistani UK women are at greater risk of being diagnosed with breast cancer which is at a later stage, more aggressive and more difficult to treat. These differences are greater in older compared with younger women, and in black Carribean and African ethnic groups rather than South Asian ethnic groups. Compared to white women, black African women are much more likely to be diagnosed with oestrogen receptor negative (ER-) breast cancer, which is harder to treat than ER+ breast cancer. They are also more likely to be diagnosed with HER2+ breast cancer, which can also be difficult to treat.

  Read more on ethnicty and breast cancer here.

  Q2. Does a family history of breast cancer put someone at a higher risk?

  Those who have inherited a specific gene mutation (e.g. a BRCA mutation) or with a strong family history of breast cancer (e.g. two first-degree relatives (mother, sister, or daughter) or one first-degree relative under 40 years who has had breast cancer) are at higher risk of getting the disease. For example having one first-degree relative (mother, sibling or daughter) who has developed breast cancer (especially at a young age) approximately doubles your risk. Having a BRCA mutation or a strong family history of breast cancer does not mean you will automatically get the disease; it means you are at higher risk. It should also be noted that most breast cancers occur in women who do not carry a single gene mutation or do not have a strong family history of the disease. Anyone can get breast cancer, although it is far more common in older women.

  Q3. What are BRCA1 and BRCA2 genes?

  BRCA1 and BRCA2 (BReast CAncer genes 1 and 2) are genes that produce proteins that help repair damaged DNA and help prevent cancer from developing.

  Women and men carry two alleles (versions) of these genes. Those who inherit harmful variants (mutations) of either allele have an increased risk of several types of cancer, most notably breast and ovarian cancer in women and breast and prostate cancer in men. These mutations cause the protein to lose its function, so DNA repair is no longer functional. We call this loss of function mutations. Those with an inherited BRCA mutation also tend to develop cancer at a younger age. BRCA mutations can be inherited from either parent, and each child of a parent carrying a BRCA mutation has a 1 in 2 chance of inheriting the mutation.

  Q4. Is there a connection between breast cancer and ovarian cancer and are the causes the same?

  There is occasionally a strong connection between breast and ovarian cancer when either is due to a single inherited gene mutation, such as a mutation in a BRCA gene. This is known as “hereditary breast and ovarian cancer syndrome”. If either cancer is hereditary, then your risk is significantly increased for both cancers.

  If your cancer is not hereditary (e.g., not due to a single inherited mutation), then there is a loose connection based on both cancers sharing several common risk factors.

  Q5. Why are taller women at a higher risk of getting breast cancer?

  A study that included 5 million women found that being tall is a risk factor for hormone-responsive breast cancer. The reasons for this are not well understood, although it’s likely that genetic factors and biological pathways which affect adult height may explain the association. For example, taller women have higher levels of insulin-like growth factor-1 (IGF-1), which also promotes cell division and inhibits programmed cell death (increasing cancer risk). Cancer incidence increases with increasing adult height for most types of cancers.

• Is there anything else that can affect my breast cancer risk?

  Q1. Does having larger breasts increase the risk of breast cancer?

  The research behind this question is inconclusive. Some early studies identified a link between having large breasts and increased breast cancer risk, but recent studies suggest an increased breast size does not appear to increase the risk of breast cancer. 

  What is more important is your breast density (i.e. how much fat tissue compared to fibrous and glandular tissue is in your breasts, which is detected by a mammogram). Moreover, the definition of a large breast in terms of size has not yet been clarified.

  Q2. Am I more at risk of breast cancer if I have breast implants?

  There is no convincing scientific evidence to show implants increase breast cancer risk. However, breast implants may make breast cancer harder to detect.

  There is also no evidence that breast reconstruction after cancer treatment carries an increased risk of breast cancer recurrence, whether or not implants are involved. Certain types of “textured” breast implants (no longer available in the EU or UK) slightly increase the risk of a rare type of lymphoma.

  Q3. Is stress a risk factor for breast cancer?

  So far, there is limited evidence of a direct link between stress and breast cancer risk, with much of the research producing conflicting results.

  Some studies have shown stress/psychological factors to increase breast cancer risk. Meanwhile, others have shown no association. However, it can be more difficult for people to keep healthy during stressful periods, so stress may indirectly increase the risk of cancer. Although again, research on this is limited.

  Q4. What does it mean to have dense breasts – is this a risk?

  High breast (or mammographic) density is a significant risk factor for breast cancer. Breasts are described as “dense” if they have lots of fibrous or glandular tissue and not much fat tissue. The density of breast tissue can only be detected on a mammogram and is not related to the size of your breasts or how they feel. Breasts are naturally more or less dense (due partly to inheritance), although breast density changes over time, and breasts tend to become less dense with age.

  Exposure to some EDCs (e.g., BPA) may increase breast density, especially if exposure occurs in the womb or during puberty. Dense breasts also make mammograms more difficult to interpret.

  Q5. Does fluoride in drinking water increase breast cancer risk?

  There is insufficient evidence to conclude that fluoride in drinking water increases breast cancer risk.  Fluoride is a substance added to drinking water to prevent tooth decay.

  Q6. Does chlorine in drinking water increase breast cancer risk?

  There is insufficient evidence to conclude that chlorine in drinking water increases breast cancer risk, although some studies claim it could. Chlorine is added to water as a disinfectant.

  Q7. Can mammograms increase the risk of breast cancer?

  Mammograms deliver very low levels of ionising radiation, which may very slightly increase breast cancer risk. 

  According to Public Health England (2017), if a woman attends all seven screening examinations between the age of 50 up to her 71st birthday, the risk of radiation-induced cancer is between 1 in 7,000 to 1 in 14,000.

  They also estimate that about 400 to 800 cancers are detected by the NHS mammography screening programme for every cancer that is radiation associated, meaning the risk of developing cancer outweighs the small risk incurred by having the mammogram.

  Q8. Does socioeconomic status affect your risk of breast cancer?

  Women who live in areas of higher socioeconomic status have an increased risk of breast cancer compared to those who live in more disadvantaged areas.

  The reasons may be associated with reproductive and hormonal factors, such as later age at first childbirth, having fewer children and less breastfeeding, and certain lifestyle factors.

  Q9. Does where you live affect your risk of breast cancer?

  Women who live in wealthier countries have an increased risk of breast cancer compared to those who live in poorer countries. The reasons may be associated with reproductive factors, such as earlier age at menarche (first period), later age at first childbirth, having fewer children, less breastfeeding, and lifestyle factors such as increased obesity, alcohol consumption, and reduced physical activity.

  Living in urban areas, as opposed to rural areas, is also associated with increased risk. The reasons for this may be due to environmental factors such as increased pollution levels in urban areas or reproductive and lifestyle factors.

  Q10. Do underwire bras increase my risk of breast cancer?

  Underwire bras do not increase your risk of breast cancer.

  The claim is based on a suggestion that underwire bras block the drainage of lymph fluid from the bottom of the breast so it can’t get back into your body, but there is no reliable scientific evidence to support this claim.

  Q11. Does night shift work increase breast cancer risk?

  It is unclear whether night shift work may increase breast cancer risk.

  In 2019, the International Agency for Research on Cancer (IARC) classified night shift work as “probably carcinogenic to humans” and stated there was limited evidence that night shift work causes breast cancer. Since 2019, numerous epidemiological studies and meta-studies have been published on this subject, including a re-evaluation of the research by the IARC in 2020 which reached the same conclusion.

  One recent study of Norwegian Offshore Petroleum Workers found night shift work may increase breast cancer risk in men. However, the Generations Study, which has looked at the data relating to over 100,000 UK women has shown no overall association between breast cancer risk and overnight working.

  A suggested reason for any potential increase in breast cancer risk in night-shift workers is that they have lower levels of the hormone melatonin, which plays a central role in regulating the body’s sleep cycle or circadian rhythm. Melatonin production peaks at night and is lower during the day. Light at night inhibits the release of this hormone into the bloodstream. Melatonin is known to be protective against breast cancer. It reduces the multiplication and spread of breast cancer cells and breast cancer stem cells (where cancers often originate), and it is anti-oestrogenic.

  Q12. Does mobile phone use increase breast cancer risk? 

  Studies looking at mobile phone use over long periods of time have shown no evidence of an increased breast cancer risk. Additionally, there is no convincing evidence that storing mobile phones in bras increases breast cancer risk, as only a few very small studies have looked into this.

  Research is still ongoing to ensure effects on cancer risk in the long-term, but none have been identified so far.

  Q13. Does having type 2 diabetes increase breast cancer risk? 

  Breast cancer incidence has previously been shown to be higher in women who have type 2 diabetes compared to those who don’t. This is also particularly true for postmenopausal women. The reasons behind this increase are still not completely understood. Still, scientists believe there could be both direct (e.g., specific changes to the body in people with type 2 diabetes may be affecting risk) and indirect (e.g., being overweight, which is a risk factor for both diseases) causes.

References

• References - FAQs

  Facts and figures:

  1. Bray F, Laversanne M, Sung H, Ferlay J, Siegel RL, Soerjomataram I, et al. Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2024;74:229–63. https://doi.org/10.3322/caac.21834.  

  2.  Ferlay J, Ervik M, Laversanne M, Colombet M, Mery L, Piñeros M, et al. Global Cancer Observatory: Cancer Today 2024. International Agency for Research on Cancer 2024. https://gco.iarc.who.int/media/globocan/factsheets/populations/900-world-fact-sheet.pdf (accessed July 8, 2025).  

  3. Xu S, Liu Y, Zhang T, Zheng J, Lin W, Cai J, et al. The Global, Regional, and National Burden and Trends of Breast Cancer From 1990 to 2019: Results From the Global Burden of Disease Study 2019. Front Oncol 2021;11:689562. https://doi.org/10.3389/fonc.2021.689562. 

  4. Cancer Research UK. Breast cancer statistics n.d. https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer#heading-Zero (accessed July 8, 2025).  

  5. Cancer Research UK. Breast cancer in men 2023. https://www.cancerresearchuk.org/about-cancer/breast-cancer/types/male-breast-cancer (accessed July 8, 2025).  

  6. Cancer Research UK. Breast cancer incidence by age. Breast Cancer Incidence (Invasive) Statistics 2024. https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer/incidence-invasive#heading-One (accessed July 8, 2025).  

  7.  Cancer Research UK. In situ breast carcinoma incidence. Breast Cancer Statistics n.d. https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer#breastcs1 (accessed July 8, 2025).  

  8. NHS Digital. Cancer incidence by main cancer group. Cancer Registration Statistics, England, 2022 2024. https://digital.nhs.uk/data-and-information/publications/statistical/cancer-registration-statistics/england-2022/incidence-by-main-cancer-group (accessed July 8, 2025).  

  9. NHS Digital. Cancer incidence by stage. Cancer Registration Statistics, England, 2022 2024. https://digital.nhs.uk/data-and-information/publications/statistical/cancer-registration-statistics/england-2022/incidence-by-stage-at-diagnosis (accessed July 8, 2025).  

  10. Cancer Research UK. Breast cancer incidence trends over time. Breast Cancer Incidence (Invasive) Statistics n.d. https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer/incidence-invasive#heading-Two (accessed July 8, 2025).  

  11. NHS Digital. Cancer Incidence by Deprivation Profile. Cancer Registration Statistics, England, 2022 2024. https://digital.nhs.uk/data-and-information/publications/statistical/cancer-registration-statistics/england-2022/incidence-by-deprivation-quintile (accessed July 15, 2025).  

  12. Delon C, Brown KF, Payne NWS, Kotrotsios Y, Vernon S, Shelton J. Differences in cancer incidence by broad ethnic group in England, 2013–2017. Br J Cancer 2022;126:1765–73. https://doi.org/10.1038/s41416-022-01718-5.  

  13.  NHS England. Screening and earlier diagnosis n.d. https://www.england.nhs.uk/cancer/early-diagnosis/screening-and-earlier-diagnosis/ (accessed July 16, 2025).  

  14. Breast Cancer UK. Why we say at least 30% 2024. https://www.breastcanceruk.org.uk/about-breast-cancer-uk/why-do-we-say-at-least-30/ (accessed July 15, 2025).  

  15.  Cancer Research UK. Breast cancer mortality. Breast Cancer Statistics n.d. https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer#breastcs2 (accessed July 8, 2025).  

  16.  Office for National Statistics. Deaths registered in England and Wales: 2023 2024. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/deaths/bulletins/deathsregistrationsummarytables/2023#leading-causes-of-death (accessed July 8, 2025).  

  17.  Office for National Statistics. Cancer survival in England – adults diagnosed 2019. https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/datasets/cancersurvivalratescancersurvivalinenglandadultsdiagnosed (accessed July 8, 2025).  

  18.  NHS Digital. NHS Breast Screening Programme, England 2020-21. Breast Screening Programme 2022. https://digital.nhs.uk/data-and-information/publications/statistical/breast-screening-programme/england—2020-21 (accessed July 8, 2025).  

  19.  Yoshida R. Hereditary breast and ovarian cancer (HBOC): review of its molecular characteristics, screening, treatment, and prognosis. Breast Cancer 2021;28:1167–80. https://doi.org/10.1007/S12282-020-01148-2.  

  20.  Cancer Research UK. Inherited genes and cancer types 2024. https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/inherited-cancer-genes-and-increased-cancer-risk/inherited-genes-and-cancer-types (accessed July 8, 2025). 

  FAQs:

  About breast cancer 

  Q1. What should I do if I think I have breast cancer? 

  NHS. Test and next steps for breast cancer in women[Internet]. [cited 2023 Jul 20]. Available from:  https://www.nhs.uk/conditions/breast-cancer-in-women/tests-and-next-steps-for-breast-cancer-in-women/ 

  Q2. How is breast cancer diagnosed? 

  NHS. Biopsy overview [Internet]. [cited 2023 Jul 21]. Available from: https://www.nhs.uk/conditions/biopsy/ 

  NHS. New imaging technology improving breast cancer diagnosis [Internet]. 2023 [cited 2023 Jul 21]. Available from: https://www.ncic.nhs.uk/news/new-imaging-technology-improving-breast-cancer-diagnosis 

  NICE. Contrast-enhanced spectral mammography for breast cancer Medtech innovation briefing [Internet]. NICE Guidance. 2022 [cited 2023 Jul 20]. Available from: www.nice.org.uk/guidance/mib304 

  Lifestyle risk factors 

  Q1. Is being overweight or obese a risk factor for breast cancer? 

  Dehesh T, Fadaghi S, Seyedi M, Abolhadi E, Ilaghi M, Shams P, et al. The relation between obesity and breast cancer risk in women by considering menstruation status and geographical variations: a systematic review and meta-analysis. BMC Womens Health 2023;23. https://doi.org/10.1186/S12905-023-02543-5 

  Humphries MP, Jordan VC, Speirs V. Obesity and male breast cancer: Provocative parallels? BMC Med 2015;13:1–9. https://doi.org/10.1186/S12916-015-0380-X 

  Reeves GK, Pirie K, Beral V, Green J, Spencer E, Bull D. Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. BMJ 2007;335:1134–9 https://doi.org/10.1136/bmj.39367.495995.AE 

  Q2. Does being overweight or obese increase the risk of breast cancer in premenopausal women? Bokobza E, Hinault C, Tiroille V, Clavel S, Bost F, Chevalier N. The Adipose Tissue at the Crosstalk Between EDCs and Cancer Development. Front Endocrinol (Lausanne) 2021;12:691658. https://doi.org/10.3389/fendo.2021.691658. 

  Darbre PD. Endocrine Disruptors and Obesity. Curr Obes Rep [Internet]. 2017 [cited 2023 Jul 21];6(1):18–27. Available from: https://pubmed.ncbi.nlm.nih.gov/28205155/ 

  Dehesh T, Fadaghi S, Seyedi M, Abolhadi E, Ilaghi M, Shams P, et al. The relation between obesity and breast cancer risk in women by considering menstruation status and geographical variations: a systematic review and meta-analysis. BMC Womens Health 2023;23. https://doi.org/10.1186/S12905-023-02543-5 

  García-Estévez L, Cortés J, Pérez S, Calvo I, Gallegos I, Moreno-Bueno G. Obesity and Breast Cancer: A Paradoxical and Controversial Relationship Influenced by Menopausal Status. Front Oncol. 2021. 11:705911. https://doi.org/10.3389/fonc.2021.705911 

  Schoemaker MJ, Nichols HB, Wright LB, Brook MN, Jones ME, O’Brien KM, et al. Adult weight change and premenopausal breast cancer risk: A prospective pooled analysis of data from 628,463 women. Int J Cancer [Internet]. 2020 [cited 2023 Jul 21];147(5):1306–14. Available from: https://pubmed.ncbi.nlm.nih.gov/32012248/ 

  Torres-De La Roche LA, Steljes I, Janni W, Friedl TWP, De Wilde RL. The Association between Obesity and Premenopausal Breast Cancer According to Intrinsic Subtypes – a Systematic Review. Geburtshilfe Frauenheilkd [Internet]. 2020 [cited 2023 Jul 21];80(6):601. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7299685/ 

  van den Brandt PA, Ziegler RG, Wang M, Hou T, Li R, Adami HO, et al. Body size and weight change over adulthood and risk of breast cancer by menopausal and hormone receptor status: a pooled analysis of 20 prospective cohort studies. Eur J Epidemiol [Internet]. 2021 [cited 2023 Jul 21];36(1):37–55. Available from: https://pubmed.ncbi.nlm.nih.gov/33128203/ 

  World Health Organization (WHO). Obesity and overweight 2024. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight 

  Q3. Is there a link between eating processed meat and breast cancer? 

  Anderson JJ, Darwis NDM, Mackay DF, Celis-Morales CA, Lyall DM, Sattar N, et al. Red and processed meat consumption and breast cancer: UK Biobank cohort study and meta-analysis. European journal of cancer [Internet]. 2018 [cited 2023 Jul 21];90:73–82. Available from: https://pubmed.ncbi.nlm.nih.gov/29274927/ 

  Diallo A, Deschasaux M, Latino-Martel P, Hercberg S, Galan P, Fassier P, et al. Red and processed meat intake and cancer risk: Results from the prospective NutriNet-Santé cohort study. Int J Cancer [Internet]. 2018 [cited 2023 Jul 21];142(2):230–7. Available from: https://pubmed.ncbi.nlm.nih.gov/28913916/ 

  Farvid MS, Stern MC, Norat T, Sasazuki S, Vineis P, Weijenberg MP, et al. Consumption of red and processed meat and breast cancer incidence: A systematic review and meta-analysis of prospective studies. Int J Cancer [Internet]. 2018 [cited 2023 Jul 21];143(11):2787–99. Available from: https://pubmed.ncbi.nlm.nih.gov/30183083/ 

  Farvid MS, Sidahmed E, Spence ND, Mante Angua K, Rosner BA, Barnett JB. Consumption of red meat and processed meat and cancer incidence: a systematic review and meta-analysis of prospective studies. Eur J Epidemiol [Internet]. 2021 [cited 2023 Jul 21];36(9):937–51. Available from: https://pubmed.ncbi.nlm.nih.gov/34455534/ 

  Q4. Can a healthy diet help to prevent breast cancer? 

  AICR, WCRF. Diet, nutrition, physical activity and breast cancer: a global perspective. Continuous Update Project Report. 2018. https://www.wcrf.org/wp-content/uploads/2021/02/Breast-cancer-report.pdf 

  Atoum M, Alzoughool F. Vitamin D and Breast Cancer: Latest Evidence and Future Steps. Breast Cancer (Auckl) [Internet]. 2017 Dec 19 [cited 2023 Jul 21];11. Available from: https://pubmed.ncbi.nlm.nih.gov/29434472/ 

  British Nutrition Foundation. Fibre [Internet]. [cited 2023 Jul 21]. Available from: https://www.nutrition.org.uk/healthy-sustainable-diets/starchy-foods-sugar-and-fibre/fibre/ 

  British Nutrition Foundation. A healthy, balanced diet [Internet]. [cited 2025 April 24]. Available from: https://www.nutrition.org.uk/creating-a-healthy-diet/a-healthy-balanced-diet/ 

  Farvid MS, Spence ND, Holmes MD, Barnett JB. Fiber consumption and breast cancer incidence: A systematic review and meta-analysis of prospective studies. Cancer [Internet]. 2020 Jul 1 [cited 2023 Jul 21];126(13):3061–75. Available from: https://onlinelibrary.wiley.com/doi/full/10.1002/cncr.32816 

  Q5. Does drinking alcohol increase my breast cancer risk? 

  AICR, WCRF. Diet, nutrition, physical activity and breast cancer: a global perspective. Continuous Update Project Report. 2018. https://www.wcrf.org/wp-content/uploads/2021/02/Breast-cancer-report.pdf 

  Freudenheim JL. Alcohol’s Effects on Breast Cancer in Women. Alcohol Res. 2020 Jun 18;40(2):11. https://doi.org/10.35946/arcr.v40.2.11 

  Sohi I, Rehm J, Saab M, Virmani L, Franklin A, Sánchez G, Jhumi M, Irshad A, Shah H, Correia D, Ferrari P, Ferreira-Borges C, Lauby-Secretan B, Galea G, Gapstur S, Neufeld M, Rumgay H, Soerjomataram I, Shield K. Alcoholic beverage consumption and female breast cancer risk: A systematic review and meta-analysis of prospective cohort studies. Alcohol Clin Exp Res (Hoboken). 2024 Dec;48(12):2222-2241. https://doi.org/10.1111/acer.15493 

  Q6. What is the ideal diet to decrease my risk of breast cancer? 

  AICR, WCRF. Diet, nutrition, physical activity and breast cancer: a global perspective. Continuous Update Project Report. 2018. https://www.wcrf.org/wp-content/uploads/2021/02/Breast-cancer-report.pdf 

  Kazemi A, Barati-Boldaji R, Soltani S, Mohammadipoor N, Esmaeilinezhad Z, Clark CCT, Babajafari S, Akbarzadeh M. Intake of Various Food Groups and Risk of Breast Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies. Adv Nutr. 2021 Jun 1;12(3):809-849. https://doi.org/10.1093/advances/nmaa147 

  Xiao Y, Xia J, Li L, Ke Y, Cheng J, Xie Y, et al. Associations between dietary patterns and the risk of breast cancer: A systematic review and meta-analysis of observational studies. Breast Cancer Research [Internet]. 2019 Jan 29 [cited 2023 Jul 21];21(1):1–22. Available from: https://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-019-1096-1 

  Q7. Does eating a vegan or vegetarian diet decrease breast cancer risk? 

  AICR, WCRF. Diet, nutrition, physical activity and breast cancer: a global perspective. Continuous Update Project Report. 2018. https://www.wcrf.org/wp-content/uploads/2021/02/Breast-cancer-report.pdf 

  Gathani T, Barnes I, Ali R, Arumugham R, Chacko R, Digumarti R, et al. Lifelong vegetarianism and breast cancer risk: A large multicentre case control study in India. BMC Womens Health [Internet]. 2017 Jan 18 [cited 2023 Jul 21];17(1):1–6. Available from: https://bmcwomenshealth.biomedcentral.com/articles/10.1186/s12905-016-0357-8 

  Rigi S, Mousavi SM, Benisi-Kohansal S, Azadbakht L, Esmaillzadeh A. The association between plant-based dietary patterns and risk of breast cancer: a case–control study. Scientific Reports 2021 11:1 [Internet]. 2021 Feb 9 [cited 2023 Jul 21];11(1):1–10. Available from: https://www.nature.com/articles/s41598-021-82659-6 

  Romanos-Nanclares A, Willett WC, Rosner BA, Collins LC, Hu FB, Toledo E, et al. Healthful and unhealthful plant-based diets and risk of breast cancer in U.S. women: Results from the nurses’ health studies. Cancer Epidemiology Biomarkers and Prevention [Internet]. 2021 Oct 1 [cited 2023 Jul 21];30(10):1921–31. Available from: https://dx.doi.org/10.1158/1055-9965.EPI-21-0352 

  World Cancer Research Fund. Healthy Living. 2023 [cited 2023 Jul 21]. Are plant-based meat alternatives better for us? Available from: https://www.wcrf-uk.org/our-blog/are-plant-based-meat-alternatives-better-for-us/ 

  Q8. Does eating organic food decrease my risk of getting breast cancer? 

  Bradbury KE, Balkwill A, Spencer EA, Roddam AW, Reeves GK, Green J, et al. Organic food consumption and the incidence of cancer in a large prospective study of women in the United Kingdom. Br J Cancer [Internet]. 2014 Mar 27 [cited 2023 Jul 21];110(9):2321–6. Available from: https://www.nature.com/articles/bjc2014148 

  Baudry J, Assmann KE, Touvier M, Allès B, Seconda L, Latino-Martel P, et al. Association of Frequency of Organic Food Consumption With Cancer Risk: Findings From the NutriNet-Santé Prospective Cohort Study. JAMA Intern Med 2018;178:1597–606. https://doi.org/10.1001/jamainternmed.2018.4357. 

  Park YMM, White A, Niehoff N, O’Brien K, Sandler D. Association Between Organic Food Consumption and Breast Cancer Risk: Findings from the Sister Study (P18-038-19). Curr Dev Nutr. 2019 Jun 1;3:nzz039.P1818-038-19. https://doi.org/10.1093/cdn/nzz039.P18-038-19 

  Rebouillat P, Vidal R, Cravedi JP, Taupier-Letage B, Debrauwer L, Gamet-Payrastre L, et al. Prospective association between dietary pesticide exposure profiles and postmenopausal breast-cancer risk in the NutriNet-Santé cohort. Int J Epidemiol [Internet]. 2021 Aug 1 [cited 2023 Jul 21];50(4):1184–98. Available from: https://pubmed.ncbi.nlm.nih.gov/33720364/ 

  Stur E, Aristizabal-Pachon AF, Peronni KC, Agostini LP, Waigel S, Chariker J, et al. Glyphosate-based herbicides at low doses affect canonical pathways in estrogen positive and negative breast cancer cell lines. PLoS One [Internet]. 2019 Jul 1 [cited 2023 Jul 21];14(7):e0219610. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0219610 

  Yang KJ, Lee J, Park HL. Organophosphate Pesticide Exposure and Breast Cancer Risk: A Rapid Review of Human, Animal, and Cell-Based Studies. Int J Environ Res Public Health [Internet]. 2020 Jul 13 [cited 2023 Jul 21];17(14):5030. Available from: https://www.mdpi.com/1660-4601/17/14/5030/htm 

  Q9. Does drinking cow’s milk increase breast cancer risk? 

  Chen L, Li M, Li H. Milk and yogurt intake and breast cancer risk A meta-analysis. Medicine [Internet]. 2019 [cited 2023 Jul 21];98(12):e14900. Available from: http://dx.doi.org/10.1097/MD.0000000000014900 

  He Y, Tao Q, Zhou F, Si Y, Fu R, Xu B, et al. The relationship between dairy products intake and breast cancer incidence: a meta-analysis of observational studies. BMC Cancer [Internet]. 2021 Oct 15 [cited 2023 Jul 21];21(1):1–12. Available from: https://bmccancer.biomedcentral.com/articles/10.1186/s12885-021-08854-w 

  Jeyaraman MM, Abou-Setta AM, Grant L, Farshidfar F, Copstein L, Lys J, et al. Dairy product consumption and development of cancer: an overview of reviews. BMJ Open [Internet]. 2019 Jan 1 [cited 2023 Jul 21];9(1):e023625. Available from: https://bmjopen.bmj.com/content/9/1/e023625 

  He Y, Tao Q, Zhou F, Si Y, Fu R, Xu B, et al. Diet, insulin-like growth factor-1 and cancer risk. Proceedings of the Nutrition Society [Internet]. 2011 [cited 2023 Jul 21];70(3):385–8. Available from: https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/diet-insulinlike-growth-factor1-and-cancer-risk/DB006BA4B70E896E51DA23BA96A740BB 

  Wu Y, Huang R, Wang M, Bernstein L, Bethea TN, Chen C, et al. Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies. Am J Clin Nutr. 2021 Aug 1;114(2):450–61. https://www.sciencedirect.com/science/article/pii/S0002916522003616?via%3Dihub 

  Zang J, Shen M, Du S, Chen T, Zou S. The Association between Dairy Intake and Breast Cancer in Western and Asian Populations: A Systematic Review and Meta-Analysis. J Breast Cancer [Internet]. 2015 Dec 1 [cited 2023 Jul 21];18(4):313–22. Available from: https://pubmed.ncbi.nlm.nih.gov/26770237/ 

  Q10. Can vitamin D supplements reduce my breast cancer risk? 

  Atoum M, Alzoughool F. Vitamin D and Breast Cancer: Latest Evidence and Future Steps. Breast Cancer (Auckl) [Internet]. 2017 Dec 19 [cited 2023 Jul 21];11. Available from: https://pubmed.ncbi.nlm.nih.gov/29434472/ 

  Atoum, M., & Alzoughool, F. (2017). Vitamin D and Breast Cancer: Latest Evidence and Future Steps. Breast cancer : basic and clinical research, 11, 1178223417749816. https://doi.org/10.1177/1178223417749816 

  Li Z, Wu L, Zhang J, Huang X, Thabane L, Li G. Effect of Vitamin D Supplementation on Risk of Breast Cancer: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Front Nutr. 2021 Apr 1;8:655727. https://www.frontiersin.org/articles/10.3389/fnut.2021.655727/full 

  Q11. Does consuming too much sugar increase breast cancer risk? 

  AICR, WCRF. Diet, nutrition, physical activity and breast cancer: a global perspective. Continuous Update Project Report. 2018. https://www.wcrf.org/wp-content/uploads/2021/02/Breast-cancer-report.pdf 

  Debras C, Chazelas E, Srour B, Kesse-Guyot E, Julia C, Zelek L, et al. Total and added sugar intakes, sugar types, and cancer risk: results from the prospective NutriNet-Santé cohort. Am J Clin Nutr. 2020 Nov 1;112(5):1267–79. https://doi.org/10.1093/ajcn/nqaa246 

  Epner M, Yang P, Wagner RW, Cohen L. Understanding the Link between Sugar and Cancer: An Examination of the Preclinical and Clinical Evidence. Cancers (Basel). 2022 Dec 8;14(24):6042. https://doi.org/10.3390/cancers14246042 

  Lu S, Qian Y, Huang X, Yu H, Yang J, Han R, et al. The association of dietary pattern and breast cancer in Jiangsu, China: A population-based case-control study. PLoS One [Internet]. 2017 Sep 1 [cited 2023 Jul 21];12(9):e0184453. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0184453 

  Q12. Does eating products containing artificial sweeteners increase breast cancer risk? 

  Debras C, Chazelas E, Srour B, Druesne-Pecollo N, Esseddik Y, de Edelenyi FS, et al. Artificial sweeteners and cancer risk: Results from the NutriNet-Santé population-based cohort study. PLoS Med [Internet]. 2022 Mar 1 [cited 2023 Jul 21];19(3):e1003950. Available from: https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003950 

  Riboli E, Beland FA, Lachenmeier DW, Marques MM, Phillips DH, Schernhammer E, et al. Carcinogenicity of aspartame, methyleugenol, and isoeugenol. Lancet Oncol [Internet]. 2023 Jul [cited 2023 Jul 21];0(0). Available from: http://www.thelancet.com/article/S1470204523003418/fulltext 

  Romanos-Nanclares A, Schernhammer E, Willett WC, Holmes MD, Chen WY, Eliassen AH. Consumption of aspartame and risk of breast cancer in the Nurses’ Health Studies, JNCI: Journal of the National Cancer Institute, Volume 117, Issue 4, April 2025, Pages 795–800, https://doi.org/10.1093/jnci/djae259 

  Yu X, Yu Z, Chen X, Liu M, Yang F, Cheung KCP. Research Progress on the Relationship Between Artificial Sweeteners and Breast Cancer. Biomedicines. 2024 Dec 18;12(12):2871. https://doi.org/10.3390/biomedicines12122871 

  Q13. Can eating soy products increase breast cancer risk? 

  Boutas I, Kontogeorgi A, Dimitrakakis C, Kalantaridou SN. Soy Isoflavones and Breast Cancer Risk: A Meta-analysis. In Vivo [Internet]. 2022 Mar 1 [cited 2023 Jul 21];36(2):556–62. Available from: https://pubmed.ncbi.nlm.nih.gov/35241506/ 

  Kazemi A, Barati-Boldaji R, Soltani S, Mohammadipoor N, Esmaeilinezhad Z, Clark CCT, et al. Intake of Various Food Groups and Risk of Breast Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies. Advances in Nutrition. 2021 May 1;12(3):809–49. https://doi.org/10.1093/advances/nmaa147 

  Messina M, Mejia SB, Cassidy A, Duncan A, Kurzer M, Nagato C, et al. Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data. Crit Rev Food Sci Nutr [Internet]. 2022 [cited 2023 Jul 21];62(21):5824–85. Available from: https://pubmed.ncbi.nlm.nih.gov/33775173/ 

  Wei Y, Lv J, Guo Y, Bian Z, Gao M, Du H, et al. Soy intake and breast cancer risk: a prospective study of 300,000 Chinese women and a dose–response meta-analysis. Eur J Epidemiol [Internet]. 2020 Jun 1 [cited 2023 Jul 21];35(6):567–78. Available from: https://link.springer.com/article/10.1007/s10654-019-00585-4 

  Q14. Does physical activity affect my risk of breast cancer? 

  Cannioto RA, Hutson A, Dighe S, McCann W, McCann SE, Zirpoli GR, et al. Physical Activity Before, During, and After Chemotherapy for High-Risk Breast Cancer: Relationships With Survival. JNCI: Journal of the National Cancer Institute [Internet]. 2021 Jan 4 [cited 2023 Jul 21];113(1):54–63. Available from: https://dx.doi.org/10.1093/jnci/djaa046 

  Gonçalves AK, Dantas Florêncio GL, Maissonnete De Atayde Silva MJ, Cobucci RN, Giraldo PC, Cote NM. Effects of physical activity on breast cancer prevention: a systematic review. J Phys Act Health [Internet]. 2014 [cited 2023 Aug 4];11(2):445–54. Available from: https://pubmed.ncbi.nlm.nih.gov/23416687/ 

  Guo W, Fensom GK, Reeves GK, Key TJ. Physical activity and breast cancer risk: results from the UK Biobank prospective cohort. British Journal of Cancer 2020 122:5 [Internet]. 2020 Jan 10 [cited 2023 Aug 4];122(5):726–32. Available from: https://www.nature.com/articles/s41416-019-0700-6 

  Spei ME, Samoli E, Bravi F, La Vecchia C, Bamia C, Benetou V. Physical activity in breast cancer survivors: A systematic review and meta-analysis on overall and breast cancer survival. Breast [Internet]. 2019 Apr 1 [cited 2023 Aug 4];44:144–52. Available from: http://www.thebreastonline.com/article/S0960977619300207/fulltext 

  Xu Y, Rogers CJ. Physical Activity and Breast Cancer Prevention: Possible Role of Immune Mediators. Front Nutr. 2020 Oct 8;7:557997. https://www.frontiersin.org/articles/10.3389/fnut.2020.557997/full 

  World Health Organization (WHO). Physical activity 2024. https://www.who.int/news-room/fact-sheets/detail/physical-activity 

  Q15. Does smoking increase breast cancer risk? 

  Betts K. Breast cancer and smoking: What is the link? https://news.cancerresearchuk.org/2024/07/09/breast-cancer-smoking-link/ (Accessed 7th May 2025) 

  Jones ME, Schoemaker MJ, Wright LB, Ashworth A, Swerdlow AJ. Smoking and risk of breast cancer in the Generations Study cohort. Breast Cancer Res [Internet]. 2017 Nov 22 [cited 2023 Jul 21];19(1). Available from: https://pubmed.ncbi.nlm.nih.gov/29162146/ 

  Park HA, Neumeyer S, Michailidou K, Bolla MK, Wang Q, Dennis J, et al. Mendelian randomisation study of smoking exposure in relation to breast cancer risk. Br J Cancer [Internet]. 2021 Oct 12 [cited 2023 Jul 21];125(8):1135–45. Available from: https://pubmed.ncbi.nlm.nih.gov/34341517/ 

  Scala M, Bosetti C, Bagnardi V, Possenti I, Specchia C, Gallus S, Lugo A. Dose-response Relationships Between Cigarette Smoking and Breast Cancer Risk: A Systematic Review and Meta-analysis. J Epidemiol. 2023 Dec 5;33(12):640-648. https://doi.org/10.2188/jea.JE20220206 

  van den Brandt PA. A possible dual effect of cigarette smoking on the risk of postmenopausal breast cancer. Eur J Epidemiol [Internet]. 2017 Aug 1 [cited 2023 Jul 21];32(8):683–90. Available from: https://pubmed.ncbi.nlm.nih.gov/28710542/ 

  Q16. Does vaping increase breast cancer risk? 

  Cancer Research UK. Is vaping harmful? [Internet]. [cited 2023 Jul 21]. Available from: https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/smoking-and-cancer/is-vaping-harmful 

  National Academies of Sciences Engineering and Medicine, Health and Medicine Division, Board on Population Health and Public Health Practice, Committee on the Review of the Health Effects of Electronic Systems Nicotine Delivery. Toxicology of E-Cigarette Constituents. In: Eaton DL, Kwan LY, Stratton K, editors. Public Health Consequences of E-Cigarettes [Internet]. Washington: National Academies Press (US); 2018 [cited 2023 Jul 21]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507171/ 

  Chemicals and the environment 

  Q1. How might exposure to certain chemicals increase breast cancer risk? 

  Gore AC, Chappell VA, Fenton SE, Flaws JA, Nadal A, Prins GS, et al. EDC-2: The Endocrine Society’s Second Scientific Statement on Endocrine-Disrupting Chemicals. Endocr Rev 2015;36:1–150. https://doi.org/10.1210/er.2015-1010. 

  Kay JE, Cardona B, Rudel RA, Vandenberg LN, Soto AM, Christiansen S, et al. Chemical Effects on Breast Development, Function, and Cancer Risk: Existing Knowledge and New Opportunities. Curr Environ Health Rep 2022;9:535–62.https://doi.org/10.1007/s40572-022-00376-2. 

  Nounu A, Kar SP, Relton CL, Richmond RC. Sex steroid hormones and risk of breast cancer: a two-sample Mendelian randomization study. Breast Cancer Research 2022;24. https://doi.org/10.1186/s13058-022-01553-9. 

  Travis RC, Key TJ. Oestrogen exposure and breast cancer risk. Breast Cancer Res [Internet]. 2003 [cited 2023 Jul 21];5(5):239. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC314432/ 

  Q2. Where are endocrine-disrupting chemicals found? 

  Breast Cancer UK. Endocrine disrupting chemicals [Internet]. 2018 [cited 2023 Jul 21]. Available from: https://cdn.breastcanceruk.org.uk/uploads/2019/08/BCUK_EDC_brief_v2_20.9.18.pdf 

  Endocrine Society. Common EDCs and Where They Are Found [Internet]. [cited 2023 Jul 21]. Available from: https://www.endocrine.org/topics/edc/what-edcs-are/common-edcs 

  Q3. Why don’t other cancer charities highlight exposures to harmful chemicals as cancer risk factors? 

  United Nations Environment Programme. Global Chemicals Outlook II: From Legacies to Innovative Solutions Programme [Internet]. 2019 [cited 2023 Jul 21]. Available from: https://www.unep.org/resources/report/global-chemicals-outlook-ii-legacies-innovative-solutions 

  WHO, UNEP. State of the Science of Endocrine Disrupting Chemicals [Internet]. 2012 [cited 2023 Jul 21]. Available from:  https://www.who.int/publications/i/item/state-of-the-science-of-endocrine-disrupting-chemicals 

  Q4. Does drinking water from plastic bottles increase breast cancer risk? 

  Kay JE, Cardona B, Rudel RA, Vandenberg LN, Soto AM, Christiansen S, et al. Chemical Effects on Breast Development, Function, and Cancer Risk: Existing Knowledge and New Opportunities. Curr Environ Health Rep 2022;9:535–62. https://doi.org/10.1007/s40572-022-00376-2. 

  Le HH, Carlson EM, Chua JP, Belcher SM. Bisphenol A is released from polycarbonate drinking bottles and mimics the neurotoxic actions of estrogen in developing cerebellar neurons. Toxicol Lett [Internet]. 2008 Jan 1 [cited 2023 Jul 21];176(2):149. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2254523/ 

  Sax L. Polyethylene terephthalate may yield endocrine disruptors. Environ Health Perspect [Internet]. 2010 Apr [cited 2023 Jul 21];118(4):445–8. Available from: https://pubmed.ncbi.nlm.nih.gov/20368129/ 

  Q5. Do antiperspirants and deodorants increase breast cancer risk? 

  Breast Cancer UK. Aluminium salts as antiperspirants [Internet]. 2019 [cited 2023 Jul 21]. Available from: https://cdn.breastcanceruk.org.uk/uploads/2019/09/short-brief-aluminium-salts-as-antiperspirants-13.9.19.pdf 

  Darbre PD. Endocrine disrupting chemicals and breast cancer cells. Advances in pharmacology [Internet]. 2021 Jan 1 [cited 2023 Jul 21];92:485–520. Available from: https://pubmed.ncbi.nlm.nih.gov/34452695/ 

  Mandriota et al. Genomic Instability Is an Early Event in Aluminium-Induced Tumorigenesis. International Journal of Molecular Sciences 2020; 21(23), 9332. https://doi.org/10.3390/ijms21239332 

  Q6. Does using products containing lavender oil increase my risk of breast cancer? 

  Cancer Research UK. Aromatherapy. https://www.cancerresearchuk.org/about-cancer/treatment/complementary-alternative-therapies/individual-therapies/aromatherapy (Accessed 23rd April 2025) 

  Endocrine Society. Chemicals in lavender and tea tree oil appear to be hormone disruptors | [Internet]. 2018 [cited 2023 Jul 21]. Available from: https://www.endocrine.org/news-and-advocacy/news-room/2018/chemicals-in-lavender-and-tea-tree-oil-appear-to-be-hormone-disruptors 

  Hawkins J, Hires C, Dunne E, Keenan L. Prevalence of endocrine disorders among children exposed to Lavender Essential Oil and Tea Tree Essential Oils. Int J Pediatr Adolesc Med. 2022 Jun 1;9(2):117–24. https://www.sciencedirect.com/science/article/pii/S2352646721000855?via%3Dihub 

  Henley et al. Prepubertal gynecomastia linked to lavender and tea tree oils. N Engl J Med 2007; Feb 1;356(5):479-85. https://doi.org/10.1056/NEJMoa064725 

  Ramsey JT, Li Y, Arao Y, Naidu A, Coons LA, Diaz A, et al. Lavender Products Associated With Premature Thelarche and Prepubertal Gynecomastia: Case Reports and Endocrine-Disrupting Chemical Activities. J Clin Endocrinol Metab [Internet]. 2019 Nov 1 [cited 2023 Jul 21];104(11):5393–405. Available from: https://dx.doi.org/10.1210/jc.2018-01880 

  Q7. How can I tell if personal care products contain Endocrine Disrupting Chemicals (EDCs)? 

  See the links in question. 

  Q8. What sunscreens should I avoid? 

  Barr L, Alamer M, Darbre PD. Measurement of concentrations of four chemical ultraviolet filters in human breast tissue at serial locations across the breast. Journal of Applied Toxicology [Internet]. 2018 Aug 1 [cited 2023 Jul 21];38(8):1112–20. Available from: https://onlinelibrary.wiley.com/doi/full/10.1002/jat.3621 

  Majhi PD, Sharma A, Roberts AL, Daniele E, Majewski AR, Chuong LM, et al. Effects of Benzophenone-3 and Propylparaben on Estrogen Receptor–Dependent R-Loops and DNA Damage in Breast Epithelial Cells and Mice. Environ Health Perspect [Internet]. 2020 Jan 1 [cited 2023 Jul 21];128(1). Available from: https://ehp.niehs.nih.gov/doi/10.1289/EHP5221 

  EcoWatch. Your Sunscreen Is Toxic: How To Find One That’s Safe for You & the Planet [Internet]. 2022 [cited 2023 Jul 21]. Available from: https://www.ecowatch.com/sunscreen-guide.html 

  Q9. Does eating food stored in plastic containers or takeaway boxes increase breast cancer risk? 

  EFSA Panel on Food Contact Materials E and PA (CEP), Lambré C, Barat Baviera JM, Bolognesi C, Chesson A, Cocconcelli PS, et al. Re-evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs. EFSA Journal 2023;21:e06857. https://doi.org/10.2903/j.efsa.2023.6857. 

  European Commission. Commission Regulation (EU) 2024/3190 of 19 December 2024 on the use of bisphenol A (BPA) and other bisphenols and bisphenol derivatives with harmonised classification for specific hazardous properties in certain materials and articles intended to come into contact with food, amending Regulation (EU) No 10/2011 and repealing Regulation (EU) 2018/213. Official Journal of the European Union 2024. http://data.europa.eu/eli/reg/2024/3190/oj 

  Mercea P. Physicochemical processes involved in migration of bisphenol A from polycarbonate. J Appl Polym Sci [Internet]. 2009 Apr 15 [cited 2023 Jul 21];112(2):579–93. Available from: https://onlinelibrary.wiley.com/doi/full/10.1002/app.29421 

  Muncke J, Andersson AM, Backhaus T, Boucher JM, Carney Almroth B, Castillo Castillo A, et al. Impacts of food contact chemicals on human health: a consensus statement. Environmental Health [Internet]. 2020 Mar 3 [cited 2023 Jul 21];19(1):1–12. Available from: https://ehjournal.biomedcentral.com/articles/10.1186/s12940-020-0572-5 

  Stillwater BJ, Bull AC, Romagnolo DF, Neumayer LA, Donovan MG, Selmin OI. Bisphenols and Risk of Breast Cancer: A Narrative Review of the Impact of Diet and Bioactive Food Components. Front Nutr. 2020 Nov 19;7:581388. https://www.frontiersin.org/articles/10.3389/fnut.2020.581388/full 

  Q10. Can my child be exposed to EDCs in the womb? 

  Kay JE, Cardona B, Rudel RA, Vandenberg LN, Soto AM, Christiansen S, et al. Chemical Effects on Breast Development, Function, and Cancer Risk: Existing Knowledge and New Opportunities. Curr Environ Health Rep 2022;9:535–62. https://doi.org/10.1007/s40572-022-00376-2. 

  Vandenberg LN, Maffini M V., Schaeberle CM, Ucci AA, Sonnenschein C, Rubin BS, et al. Perinatal exposure to the xenoestrogen bisphenol-A induces mammary intraductal hyperplasias in adult CD-1 mice. Reproductive Toxicology. 2008 Nov 1;26(3–4):210–9. https://www.sciencedirect.com/science/article/abs/pii/S0890623808002451?via%3Dihub 

  Wormsbaecher C, Hindman AR, Avendano A, Cortes-Medina M, Jones CE, Bushman A, et al. In utero estrogenic endocrine disruption alters the stroma to increase extracellular matrix density and mammary gland stiffness. Breast Cancer Research [Internet]. 2020 May 5 [cited 2023 Jul 21];22(1):1–12. Available from: https://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-020-01275-w 

  Q11. Does exposure to parabens affect breast cancer risk? 

  Hager E, Chen J, Zhao L. Minireview: Parabens Exposure and Breast Cancer. Int J Environ Res Public Health 2022;19. https://doi.org/10.3390/ijerph19031873. 

  Mogus JP, Laplante CD, Bansal R, Matouskova K, Schneider BR, Daniele E, et al. Exposure to Propylparaben During Pregnancy and Lactation Induces Long-Term Alterations to the Mammary Gland in Mice. Endocrinology [Internet]. 2021 Jun 1 [cited 2023 Jul 21];162(6). Available from: https://pubmed.ncbi.nlm.nih.gov/33724348/ 

  Pugazhendhi D, Pope GS, Darbre PD. Oestrogenic activity of p-hydroxybenzoic acid (common metabolite of paraben esters) and methylparaben in human breast cancer cell lines. Journal of Applied Toxicology 2005;25:301–9. https://doi.org/10.1002/jat.1066 

  Shen X, Liang J, Zheng L, Wang H, Wang Z, Ji Q, et al. Ultrasound-assisted dispersive liquid-liquid microextraction followed by gas chromatography–mass spectrometry for determination of parabens in human breast tumor and peripheral adipose tissue. Journal of Chromatography B 2018;1096:48–55. https://doi.org/10.1016/j.jchromb.2018.08.004 

  Tong JH, Elmore S, Huang SS, Tachachartvanich P, Manz K, Pennell K, et al. Chronic Exposure to Low Levels of Parabens Increases Mammary Cancer Growth and Metastasis in Mice. Endocrinology 2023;164. https://doi.org/10.1210/endocr/bqad007 

  Q12. What are microplastics, and can they affect breast cancer risk? 

  Britannica. Microplastics [Internet]. 2022 [cited 2023 Jul 21]. Available from: https://www.britannica.com/technology/microplastic 

  Leslie HA, van Velzen MJM, Brandsma SH, Vethaak AD, Garcia-Vallejo JJ, Lamoree MH. Discovery and quantification of plastic particle pollution in human blood. Environ Int. 2022 May 1;163:107199. https://www.sciencedirect.com/science/article/pii/S0160412022001258 

  Munoz-Pineiro MA. MICROPLASTICS: Focus on Food and Health. Publications Office of the European Union [Internet]. 2018 [cited 2023 Jul 21];123–52. Available from: https://publications.jrc.ec.europa.eu/repository/handle/JRC110629 

  Ragusa A, Notarstefano V, Svelato A, Belloni A, Gioacchini G, Blondeel C, et al. Raman Microspectroscopy Detection and Characterisation of Microplastics in Human Breastmilk. Polymers (Basel) [Internet]. 2022 Jul 1 [cited 2023 Jul 21];14(13). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9269371/ 

  Q13. What are forever chemicals? 

  CHEMTrust. PFAS – the ’Forever Chemicals [Internet]. Vol. 126. Public Health Services, US Dept of Health and Human Services; 2018 [cited 2023 Jul 21]. Available from: https://chemtrust.org/pfas/ 

  Feng Y, Bai Y, Lu Y, Chen M, Fu M, Guan X, et al. Plasma perfluoroalkyl substance exposure and incidence risk of breast cancer: A case-cohort study in the Dongfeng-Tongji cohort. Environmental Pollution. 2022 Aug 1;306:119345. https://www.sciencedirect.com/science/article/abs/pii/S0269749122005590 

  Jiang H, Liu H, Liu G, Yu J, Liu N, Jin Y, et al. Associations between Polyfluoroalkyl Substances Exposure and Breast Cancer: A Meta-Analysis. Toxics 2022;10:318. https://doi.org/10.3390/toxics10060318. 

  Mancini FR, Cano-Sancho G, Gambaretti J, Marchand P, Boutron-Ruault MC, Severi G, et al. Perfluorinated alkylated substances serum concentration and breast cancer risk: Evidence from a nested case-control study in the French E3N cohort. Int J Cancer [Internet]. 2020 Feb 15 [cited 2023 Jul 21];146(4):917–28. Available from: https://onlinelibrary.wiley.com/doi/full/10.1002/ijc.32357 

  Q14. What is an ‘obesogen’? 

  Darbre PD. Endocrine Disruption and Disorders of Energy Metabolism. Endocrine Disruption and Human Health. 2015 Jan 1;273–85. https://www.sciencedirect.com/science/article/abs/pii/B9780128011393000156 

  Reproductive factors, natural and synthetic hormones 

  Q1. Is breast cancer during pregnancy common? 

  Allouch S, Gupta I, Malik S, Al Farsi HF, Vranic S, Al Moustafa AE. Breast Cancer During Pregnancy: A Marked Propensity to Triple-Negative Phenotype. Front Oncol. 2020 Dec 23;10:580345. https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2020.580345/full 

  Cancer Research UK. Breast cancer during pregnancy [Internet]. [cited 2023 Jul 24]. Available from: https://www.cancerresearchuk.org/about-cancer/breast-cancer/living-with/breast-cancer-during-pregnancy 

  Q2. How does age at the birth of a first child affect your breast cancer risk? 

  Borges VF, Lyons TR, Germain D, Schedin P. Postpartum involution and cancer: an opportunity for targeted breast cancer prevention and treatments? Cancer Res. 2020;80:1790–8. https://doi.org/10.1158/0008-5472.CAN-19-3448 

  Nichols HB, Schoemaker MJ, Cai J, Xu J, Wright LB, Brook MN, et al. Breast cancer risk after recent childbirth: A pooled analysis of 15 prospective studies. Ann Intern Med. 2019 Jan 1;170(1):22–30. https://pubmed.ncbi.nlm.nih.gov/30534999/ 

  Slepicka PF, Cyrill SL, dos Santos CO. Pregnancy and Breast Cancer: Pathways to Understand Risk and Prevention. Trends Mol Med [Internet]. 2019 Oct 1 [cited 2023 Jul 24];25(10):866–81. Available from: http://www.cell.com/article/S1471491419301650/fulltext 

  Q3. Does breastfeeding reduce the risk of breast cancer? 

  Fortner RT, Sisti J, Chai B, Collins LC, Rosner B, Hankinson SE, et al. Parity, breastfeeding, and breast cancer risk by hormone receptor status and molecular phenotype: Results from the Nurses’ Health Studies. Breast Cancer Research [Internet]. 2019 Mar 12 [cited 2023 Jul 24];21(1):1–9. Available from: https://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-019-1119-y 

  Stordal B. Breastfeeding reduces the risk of breast cancer: A call for action in high-income countries with low rates of breastfeeding. Cancer Med [Internet]. 2023 Feb 1 [cited 2023 Jul 24];12(4):4616–25. Available from: https://onlinelibrary.wiley.com/doi/full/10.1002/cam4.5288 

  World Cancer Research Fund. Lactation (breastfeeding) and the risk of cancer [Internet]. [cited 2023 Jul 24]. Available from: https://www.wcrf.org/dietandcancer/lactation-breastfeeding/ 

  Q4. Does HRT cause breast cancer?  

  Vinogradova Y, Coupland C, Hippisley-Cox J. Use of hormone replacement therapy and risk of breast cancer: nested case-control studies using the QResearch and CPRD databases. BMJ [Internet]. 2020 Oct 28 [cited 2023 Jul 27];371. Available from: https://www.bmj.com/content/371/bmj.m3873 

  Q5. Is it true that I’m more at risk if I don’t have children? 

  Britt K, Ashworth A, Smalley M. Pregnancy and the risk of breast cancer. Endocr Relat Cancer [Internet]. 2007 Dec [cited 2023 Jul 27];14(4):907–33. Available from: https://pubmed.ncbi.nlm.nih.gov/18045947/ 

  Li C, Fan Z, Lin X, Cao M, Song F, Song F. Parity and risk of developing breast cancer according to tumor subtype: A systematic review and meta-analysis. Cancer Epidemiol. 2021 Dec;75:102050. doi: 10.1016/j.canep.2021.102050. Epub 2021 Oct 24. PMID: 34706325. https://doi.org/10.1016/j.canep.2021.102050 

  Husby A, Wohlfahrt J, Øyen N, Melbye M. Pregnancy duration and breast cancer risk. Nat Commun [Internet]. 2018 Dec 1 [cited 2023 Jul 27];9(1). Available from: https://pubmed.ncbi.nlm.nih.gov/30353005/ 

  Q6. If I’m on a contraceptive pill or another type of hormonal contraception, am I at increased breast cancer risk? 

  Conz L, Mota BS, Bahamondes L, Teixeira Dória M, Françoise Mauricette Derchain S, Rieira R, et al. Levonorgestrel-releasing intrauterine system and breast cancer risk: A systematic review and meta-analysis. Acta Obstet Gynecol Scand [Internet]. 2020 Aug 1 [cited 2023 Jul 27];99(8):970–82. Available from: https://pubmed.ncbi.nlm.nih.gov/31990981/ 

  Fitzpatrick D, Pirie K, Reeves G, Green J, Beral V. Combined and progestagen-only hormonal contraceptives and breast cancer risk: A UK nested case–control study and meta-analysis. PLoS Med [Internet]. 2023 Mar 1 [cited 2023 Jul 27];20(3):e1004188. Available from: https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1004188 

  Karlsson T, Johansson T, Hoglund J, Ek WE, Johansson Å. Time-dependent effects of oral contraceptive use on breast, ovarian, and endometrial cancers. Cancer Res [Internet]. 2021 Feb 15 [cited 2023 Jul 27];81(4):1153–62. Available from: https://dx.doi.org/10.1158/0008-5472.CAN-20-2476 

  Samson M, Porter N, Orekoya O, Hebert JR, Adams SA, Bennett CL, et al. Progestin and breast cancer risk: a systematic review. Breast Cancer Res Treat [Internet]. 2016 Jan 1 [cited 2023 Jul 27];155(1):3–12. Available from: https://link.springer.com/article/10.1007/s10549-015-3663-1 

  Silva FR, Grande AJ, Lacerda Macedo AC, Colonetti T, Rocha MC, Rodrigues Uggioni ML, et al. Meta-Analysis of Breast Cancer Risk in Levonorgestrel-Releasing Intrauterine System Users. Clin Breast Cancer [Internet]. 2021 Dec 1 [cited 2023 Jul 27];21(6):497–508. Available from: https://pubmed.ncbi.nlm.nih.gov/34045174/ 

  Q7. Why are high levels of oestrogen potentially harmful? 

  Santen RJ, Yue W, Wang JP. Estrogen metabolites and breast cancer. Steroids [Internet]. 2015 May 26 [cited 2023 Jul 27];99(Pt A):61–6. Available from: https://pubmed.ncbi.nlm.nih.gov/25168343/ 

  Travis RC, Key TJ. Oestrogen exposure and breast cancer risk. Breast Cancer Res [Internet]. 2003 [cited 2023 Jul 27];5(5):239. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC314432/ 

  Q8. Do transgender women have an increased risk of breast cancer? 

  De Blok CJM, Wiepjes CM, Nota NM, Van Engelen K, Adank MA, Dreijerink KMA, et al. Breast cancer risk in transgender people receiving hormone treatment: nationwide cohort study in the Netherlands. BMJ [Internet]. 2019 [cited 2023 Jul 27];365. Available from: https://pubmed.ncbi.nlm.nih.gov/31088823/ 

  Iwamoto SJ, Defreyne J, Rothman MS, Van Schuylenbergh J, Van de Bruaene L, Motmans J, et al. Health considerations for transgender women and remaining unknowns: a narrative review. Ther Adv Endocrinol Metab [Internet]. 2019 [cited 2023 Jul 27];10. Available from: https://pubmed.ncbi.nlm.nih.gov/31516689/ 

  Q9. Do transgender men have an increased risk of breast cancer? 

  De Blok CJM, Wiepjes CM, Nota NM, Van Engelen K, Adank MA, Dreijerink KMA, et al. Breast cancer risk in transgender people receiving hormone treatment: nationwide cohort study in the Netherlands. BMJ [Internet]. 2019 [cited 2023 Jul 27];365. Available from: https://pubmed.ncbi.nlm.nih.gov/31088823/ 

  Fledderus AC, Gout HA, Ogilvie AC, Van Loenen DKG. Breast malignancy in female-to-male transsexuals: systematic review, case report, and recommendations for screening. The Breast [Internet]. 2020 [cited 2023 Jul 27];53:92–100. Available from: https://doi.org/10.1016/j.breast.2020.06.008 

  Genetics and family history 

  Q1. Are there any ethnic groups in the UK more at risk of breast cancer? 

  Gathani T, Ali R, Balkwill A, Green J, Reeves G, Beral V, et al. Ethnic differences in breast cancer incidence in England are due to differences in known risk factors for the disease: prospective study. Br J Cancer [Internet]. 2014 Jan 1 [cited 2023 Jul 27];110(1):224. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3887283/ 

  Gathani T, Reeves G, Broggio J, Barnes I. Ethnicity and the tumour characteristics of invasive breast cancer in over 116,500 women in England. British Journal of Cancer 2021 125:4 [Internet]. 2021 May 26 [cited 2023 Jul 27];125(4):611–7. Available from: https://www.nature.com/articles/s41416-021-01409-7 

  Haiman CA, Chen GK, Vachon CM, Canzian F, Dunning A, Millikan RC, et al. A common variant at the TERT-CLPTM1L locus is associated with estrogen receptor-negative breast cancer. Nat Genet [Internet]. 2011 Dec [cited 2023 Jul 27];43(12):1210–4. Available from: https://pubmed.ncbi.nlm.nih.gov/22037553/ 

  KB K, JL H, DR B, KA P, TM M, MJ RB, et al. Risks of Breast, Ovarian, and Contralateral Breast Cancer for BRCA1 and BRCA2 Mutation Carriers. JAMA [Internet]. 2017 Jun 20 [cited 2023 Jul 27];317(23):2402–16. Available from: https://pubmed.ncbi.nlm.nih.gov/28632866/ 

  Manchanda R, Loggenberg K, Sanderson S, Burnell M, Wardle J, Gessler S, et al. Population testing for cancer predisposing BRCA1/BRCA2 mutations in the Ashkenazi-Jewish community: a randomized controlled trial. J Natl Cancer Inst [Internet]. 2014 Jan 1 [cited 2023 Jul 27];107(1). Available from: https://pubmed.ncbi.nlm.nih.gov/25435541/ 

  Shirley MH, Barnes I, Sayeed S, Finlayson A, Ali R. Incidence of breast and gynaecological cancers by ethnic group in England, 2001-2007: A descriptive study. BMC Cancer [Internet]. 2014 Dec 18 [cited 2023 Jul 27];14(1):1–10. Available from: https://bmccancer.biomedcentral.com/articles/10.1186/1471-2407-14-979 

  Breast Cancer UK, Breast cancer risk and ethnicity explained. [Internet] October 2023. Available from: https://www.breastcanceruk.org.uk/breast-cancer-risk-and-ethnicity-explained/ 

  Q2. Does a family history of breast cancer put someone at a higher risk? 

  Economopoulou P, Dimitriadis G, Psyrri A. Beyond BRCA: New hereditary breast cancer susceptibility genes. Cancer Treat Rev [Internet]. 2015 Jan 1 [cited 2023 Jul 27];41(1):1–8. Available from: http://www.cancertreatmentreviews.com/article/S0305737214001741/fulltext 

  Breast Cancer UK, Are you susceptible to breast cancer. [Internet] November 2024 [cited 2025 March 19] Available from: https://www.breastcanceruk.org.uk/about-breast-cancer/are-you-susceptible-to-breast-cancer/ 

  Q3. What are BRCA1 and BRCA2 genes? 

  National Cancer Institute. BRCA Gene Mutations: Cancer Risk and Genetic Testing Fact Sheet [Internet]. 2020 [cited 2023 Jul 27]. Available from: https://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet#what-are-brca1-and-brca2 

  The Royal Marsden NHS Foundation Trust. A beginner’s guide to BRCA1 and BRCA2. 2013. Available from: https://patientinfolibrary.royalmarsden.nhs.uk/brca1brac2 

  National Cancer Institute (2024) BRCA Gene Mutations: Cancer Risk and Genetic Testing. https://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet 

  Q4. Is there a connection between breast cancer and ovarian cancer and are the causes the same? 

  Genomics Education Programme. Hereditary breast and ovarian cancer [Internet]. 2020 [cited 2023 Jul 27]. Available from: https://www.genomicseducation.hee.nhs.uk/documents/hereditary-breast-and-ovarian-cancer/ 

  Cancer.Net. Hereditary Breast and Ovarian Cancer [Internet]. 2020 [cited 2023 Jul 27]. Available from: https://www.cancer.net/cancer-types/hereditary-breast-and-ovarian-cancer 

  Q5. Why are taller women at a higher risk of getting breast cancer? 

  Zhang B, Shu XO, Delahanty RJ, Zeng C, Michailidou K, Bolla MK, et al. Height and Breast Cancer Risk: Evidence From Prospective Studies and Mendelian Randomization. J Natl Cancer Inst [Internet]. 2015 Nov 1 [cited 2023 Jul 27];107(11). Available from: https://pubmed.ncbi.nlm.nih.gov/26296642/ 

  Other frequently asked questions 

  Q1. Does having larger breasts increase the risk of breast cancer? 

  Hsieh C c, Trichopoulos D. Breast size, handedness and breast cancer risk. Eur J Cancer Clin Oncol. 1991 Jan 1;27(2):131–5. https://www.sciencedirect.com/science/article/abs/pii/027753799190469T?via%3Dihub 

  Ooi BNS, Loh H, Ho PJ, Milne RL, Giles G, Gao C, et al. The genetic interplay between body mass index, breast size and breast cancer risk: a Mendelian randomization analysis. Int J Epidemiol [Internet]. 2019 Jun 1 [cited 2023 Jul 27];48(3):781–94. Available from: https://academic.oup.com/ije/article/48/3/781/5523691 

  Sellahewa C, Nightingale P, Carmichael AR. Women with large breasts are at an increased risk of advanced breast cancer. International Seminars in Surgical Oncology [Internet]. 2008 Jun 30 [cited 2023 Jul 27];5(1):1–4. Available from: https://issoonline.biomedcentral.com/articles/10.1186/1477-7800-5-16 

  Q2. Am I more at risk of breast cancer if I have breast implants? 

  Brett EA, Aitzetmüller MM, Sauter MA, Huemer GM, Machens HG, Duscher D. Breast cancer recurrence after reconstruction: know thine enemy. Oncotarget [Internet]. 2018 Jun 12 [cited 2023 Jul 27];9(45):27895–906. Available from: https://pubmed.ncbi.nlm.nih.gov/29963246/ 

  Jones JL, Hanby AM, Wells C, Calaminici M, Johnson L, Turton P, et al. Breast implant-associated anaplastic large cell lymphoma (BIA-ALCL): an overview of presentation and pathogenesis and guidelines for pathological diagnosis and management. Histopathology [Internet]. 2019 Dec 1 [cited 2023 Jul 27];75(6):787–96. Available from: https://onlinelibrary.wiley.com/doi/full/10.1111/his.13932 

  Noels EC, Lapid O, Lindeman JHN, Bastiaannet E. Breast implants and the risk of breast cancer: a meta-analysis of cohort studies. Aesthet Surg J [Internet]. 2015 Jan 1 [cited 2023 Jul 27];35(1):55–62. Available from: https://pubmed.ncbi.nlm.nih.gov/25568234/ 

  Q3. Is stress a risk factor for breast cancer? 

  Chiriac VF, Baban A, Dumitrascu DL. Psychological stress and breast cancer incidence: a systematic review. Clujul Med [Internet]. 2018 [cited 2023 Jul 27];91(1):18–26. Available from: https://pubmed.ncbi.nlm.nih.gov/29440947/ 

  Cancer Research UK. Can stress cause cancer? [Internet]. [cited 2023 Jul 27]. Available from: https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/cancer-myths/can-stress-cause-cancer 

  Mohan A, Huybrechts I, Michels N. Psychosocial stress and cancer risk: a narrative review. Eur J Cancer Prev [Internet]. 2022 Nov 1 [cited 2023 Jul 27];31(6):585–99. Available from: https://pubmed.ncbi.nlm.nih.gov/35352705/ 

  Pereira MA, Araújo A, Simões M, Costa C. Influence of Psychological Factors in Breast and Lung Cancer Risk – A Systematic Review. Front Psychol [Internet]. 2022 Jan 3 [cited 2023 Jul 27];12. Available from: https://pubmed.ncbi.nlm.nih.gov/35046872/ 

  Schoemaker MJ, Jones ME, Wright LB, Griffin J, McFadden E, Ashworth A, et al. Psychological stress, adverse life events and breast cancer incidence: a cohort investigation in 106,000 women in the United Kingdom. Breast Cancer Res [Internet]. 2016 Jul 15 [cited 2023 Jul 27];18(1). Available from: https://pubmed.ncbi.nlm.nih.gov/27418063/ 

  Q4. What does it mean to have dense breasts – is this a risk? 

  Sprague BL, Trentham-Dietz A, Hedman CJ, Wang J, Hemming JDC, Hampton JM, et al. Circulating serum xenoestrogens and mammographic breast density. Breast Cancer Research [Internet]. 2013 May 27 [cited 2023 Jul 27];15(3):1–8. Available from: https://breast-cancer-research.biomedcentral.com/articles/10.1186/bcr3432 

  Q5. Does fluoride in drinking water increase breast cancer risk? 

  National Cancer Institute. Fluoridated Water. https://www.cancer.gov/about-cancer/causes-prevention/risk/myths/fluoridated-water-fact-sheet (Accessed 7th May 2025) 

  Q6. Does chlorine in drinking water increase breast cancer risk? 

  IARC Working Group on the Evaluation of Carcinogenic Risks to Humans., International Agency for Research on Cancer. Some Chemicals that Cause Tumours of the Kidney or Urinary Bladder in Rodents and Some Other Substances. World Health Organization, International Agency for Research on Cancer; 1999. https://publications.iarc.fr/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Some-Chemicals-That-Cause-Tumours-Of-The-Kidney-Or-Urinary-Bladder-In-Rodents-And-Some-Other-Substances-1999 

  Q7. Can mammograms increase the risk of breast cancer? 

  GOV.UK. NHS breast screening: helping you decide [Internet]. 2021 [cited 2023 Jul 27]. Available from: https://www.gov.uk/government/publications/breast-screening-helping-women-decide/nhs-breast-screening-helping-you-decide 

  Q8. Does socioeconomic status affect your risk of breast cancer? 

  Li, S., He, Y., Liu, J. et al. An umbrella review of socioeconomic status and cancer. Nat Commun 15, 9993 (2024). https://doi.org/10.1038/s41467-024-54444-2 

  Sung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J Clin [Internet]. 2021 May 1 [cited 2023 Jul 27];71(3):209–49. Available from: https://onlinelibrary.wiley.com/doi/full/10.3322/caac.21660 

  Q9. Does where you live affect your risk of breast cancer? 

  Sharp L, Donnelly D, Hegarty A, Carsin AE, Deady S, McCluskey N, et al. Risk of several cancers is higher in urban areas after adjusting for socioeconomic status. Results from a two-country population-based study of 18 common cancers. J Urban Health [Internet]. 2014 [cited 2023 Jul 27];91(3):510–25. Available from: https://pubmed.ncbi.nlm.nih.gov/24474611/ 

  National Cancer Registration and Analysis Service. The effect of rurality on cancer incidence and mortality [Internet]. [cited 2023 Jul 27]. Available from: http://www.ncin.org.uk/publications/data_briefings/rurality 

  Q10. Do underwire bras increase my risk of breast cancer? 

  Chen L, Malone KE, Li CI. Bra wearing not associated with breast cancer risk: A population-based case-control study. Cancer Epidemiology Biomarkers and Prevention [Internet]. 2014 Oct 1 [cited 2023 Jul 27];23(10):2181–5. Available from: https://dx.doi.org/10.1158/1055-9965.EPI-14-0414 

  Q11. Does night shift work increase breast cancer risk? 

  Gehlert S, Clanton M, Group on behalf of the SW and BCSA. Shift Work and Breast Cancer. Int J Environ Res Public Health [Internet]. 2020 Dec 2 [cited 2023 Jul 27];17(24):1–8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7767214/ 

  Hill SM, Belancio VP, Dauchy RT, Xiang S, Brimer S, Mao L, et al. Melatonin: an inhibitor of breast cancer. Endocr Relat Cancer [Internet]. 2015 Jun 1 [cited 2023 Jul 27];22(3):R183–204. Available from: https://pubmed.ncbi.nlm.nih.gov/25876649/ 

  IARC Monographs Vol 124 group. Carcinogenicity of night shift work. Lancet Oncol [Internet]. 2019 Aug 1 [cited 2023 Jul 27];20(8):1058–9. Available from: https://pubmed.ncbi.nlm.nih.gov/31281097/ 

  Liu FC, Veierød MB, Kjærheim K, Robsahm TE, Ghiasvand R, Babigumira R, et al. Excess risk of male breast cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort: a possible link to extreme night shift work? Breast Cancer Res [Internet]. 2021 Dec 1 [cited 2023 Jul 27];23(1). Available from: https://pubmed.ncbi.nlm.nih.gov/34794511/ 

  Lopes J, Arnosti D, Trosko JE, Tai MH, Zuccari D. Melatonin decreases estrogen receptor binding to estrogen response elements sites on the oct4 gene in human breast cancer stem cells. Genes Cancer [Internet]. 2016 May 1 [cited 2023 Jul 27];7(5–6):209–17. Available from: https://www.genesandcancer.com/article/107/text/ 

  Manouchehri E, Taghipour A, Ghavami V, Ebadi A, Homaei F, Latifnejad Roudsari R. Night-shift work duration and breast cancer risk: an updated systematic review and meta-analysis. BMC Womens Health [Internet]. 2021 Dec 1 [cited 2023 Jul 27];21(1):1–16. Available from: https://bmcwomenshealth.biomedcentral.com/articles/10.1186/s12905-021-01233-4 

  Jones ME, Schoemaker MJ, McFadden EC, Wright LB, Johns LE, Swerdlow AJ. Night shift work and risk of breast cancer in women: the Generations Study cohort. British Journal of Cancer. 2019 Jul [cited 2024 May 22];121(2):172-179. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6738051/ 

  Q12. Does mobile phone use increase breast cancer risk? 

  Röösli M, Lagorio S, Schoemaker MJ, Schüz J, Feychting M. Brain and Salivary Gland Tumors and Mobile Phone Use: Evaluating the Evidence from Various Epidemiological Study Designs. Annu Rev Public Health [Internet]. 2019 Apr 1 [cited 2023 Jul 27];40:221–38. Available from: https://pubmed.ncbi.nlm.nih.gov/30633716/ 

  Schüz J, Jacobsen R, Olsen JH, Boice JD, McLaughlin JK, Johansen C. Cellular telephone use and cancer risk: update of a nationwide Danish cohort. J Natl Cancer Inst [Internet]. 2006 Dec 6 [cited 2023 Jul 27];98(23):1707–13. Available from: https://pubmed.ncbi.nlm.nih.gov/17148772/ 

  West JG, Kapoor NS, Liao SY, Chen JW, Bailey L, Nagourney RA. Multifocal Breast Cancer in Young Women with Prolonged Contact between Their Breasts and Their Cellular Phones. Case Rep Med [Internet]. 2013 [cited 2023 Jul 27];2013. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3789302/ 

  Q13. Does having type 2 diabetes increase breast cancer risk? 

  Diabetes.co.uk. Breast Cancer and Diabetes [Internet]. 2019 [cited 2023 Jul 27]. Available from: https://www.diabetes.co.uk/diabetes-complications/breast-cancer.html 

  Hardefeldt PJ, Edirimanne S, Eslick GD. Diabetes increases the risk of breast cancer: a meta-analysis. Endocr Relat Cancer [Internet]. 2012 Dec 1 [cited 2023 Jul 27];19(6):793–803. Available from: https://erc.bioscientifica.com/view/journals/erc/19/6/793.xml 

  Lu Y, Hajjar A, Cryns VL, Trentham-Dietz A, Gangnon RE, Heckman-Stoddard BM, et al. Breast cancer risk for women with diabetes and the impact of metformin: A meta-analysis. Cancer Med [Internet]. 2023 May 1 [cited 2023 Jul 27];12(10):11703–18. Available from: https://pubmed.ncbi.nlm.nih.gov/36533539/