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Q1. Do antiperspirants and deodorants increase breast cancer risk? There is some scientific evidence that endocrine disrupting chemicals found in deodorants and antiperspirants may increase breast cancer risk. Most antiperspirants contain aluminium salts and some scientists believe these may increase breast cancer risk. Other types of deodorants contain perfume and anti-microbial agents such as parabens; some of these are EDCs which may be linked to breast cancer.
Q2. Am I more at risk of breast cancer if I have breast implants? There is little or 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 being overweight a breast cancer risk? Yes, being overweight when women have reached the menopause is a risk factor for breast cancer.
Q4. Is it true that I’m more at risk if I don’t have children? Yes. There is considerable evidence to show that women who haven’t given birth have an increased risk of breast cancer, compared to those who’ve given birth before the age of 30. Having more children and at a younger age reduces risk even more.
Q5. Does smoking increase breast cancer risk? Yes, smoking does increase breast cancer risk slightly. Recent studies and meta-analyses conclude there is a modest increase in breast cancer risk for those who smoke, especially for pre-menopausal women and those who started at a young age.
Q6. Does drinking water from plastic bottles increase breast cancer risk? Some types of plastic bottles contain bisphenols (found in polycarbonate plastics) or phthalates (found in recycled PET plastic recycling code 1) which may be linked to an increased risk of breast cancer. If plastic drinks bottles are used repeatedly, and especially if they are heated, these chemicals can leach out into liquids. Long-term exposure to these and other oestrogen mimics may contribute to increased breast cancer risk.
Q7. If I’m a transgender women do I have an increased risk of breast cancer? Yes, according to a recent Dutch study, 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 men who have not undergone treatment. Transgender women are 47 times more likely to develop breast cancer compared to men. However, they are still less likely to develop breast cancer compared to women who have not undergone hormone treatment.
Q8. 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.
Q9. Is there a link between eating processed meat and breast cancer? Yes, there is convincing evidence that increased consumption of processed meats such as bacon and salami slightly increases breast cancer risk.
Q10. Do chemicals increase the risk of breast cancer? Not all chemicals are harmful – water is a chemical for example. However, some chemicals can cause cancer; these are known as carcinogens and others can interfere with our hormones; these are knowns as endocrine (or hormone) disrupting chemicals (EDCs). Some EDCs mimic the activities of oestrogen. And high levels of oestrogen in your body increase your risk of getting breast cancer. Many everyday products contain known, or suspected, EDCs. These products can range from plastics and packaging to cosmetics, and furniture. Currently chemicals regulation is inadequate to help protect us against exposure to EDCs, although the EU is beginning to tackle this problem in certain areas. For full details see our Chemicals and Environment section.
Q11. If I have a family history of breast cancer am I likely to get it? 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. Having one first degree relative diagnosed with breast cancer approximately doubles your risk and risk is higher when you have a strong family history of the disease.
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 women of mature age.
Q12. Why are taller women at higher risk of getting breast cancer? A study which 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. It is 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.
Q13. Is stress a risk factor for breast cancer? It is unclear whether stress is a major risk factor for breast cancer. A 2016 study of over 100,000 UK women found no association between breast cancers and stress. However, other studies have identified a link.
Q14. What does it mean to have dense breasts – is this a risk? High breast (or mammographic) density is a 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 does change over time, and breasts tend to become less dense with age. Exposure to some EDCs (e.g. BPA) may increase breast density, especially if it occurs in the womb or during puberty. Dense breasts also make mammograms more difficult to interpret.
Q15. Does HRT cause breast cancer? Hormone replacement therapy, or HRT, increases breast cancer risk – especially combined HRT (a combination of oestrogen and progestogen). The longer HRT is taken, the higher the risk. Risk is reduced when HRT is stopped and lessens over time, although some excess risk persists for more than 10 years, after use has stopped. Most studies have found HRT containing oestrogen only slightly elevates breast cancer risk. However, this type of therapy may not be suitable for all women.
Q16. If I’m on a contraceptive pill or another type of hormonal contraception am I at increased breast cancer risk? The contraceptive pill contains synthetic oestrogen and/or synthetic progestogen. Studies have shown use of combined oral contraceptives (oestrogen and progestogen) slightly increases breast cancer risk. The risk is no longer evident 10 years after use has stopped. Some studies suggest progestogen-only contraceptives may not be associated with increased risk. More studies are needed to confirm this. Other types of hormonal contraceptives include injections and hormone releasing intrauterine systems which contain progestogen, and patches and vaginal rings which use both oestrogen and progestogen. There are fewer studies into risk associated with these types of contraceptives, although the risks are thought to be similar to the contraceptive pill. Some studies have indicated that use of injections increases breast cancer risk, although more studies are needed to confirm this.
Q17. 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). One explanation is that oestrogen encourages certain cell types, including breast cells, to divide more often. The more a cell divides, the more likely mutations will accumulate. The accumulation of particular mutations in breast cells can lead to breast cancer. Oestrogen also encourages growth of oestrogen receptor positive breast tumours.
Q18. Does fluoride in drinking water increase breast cancer risk? No studies have demonstrated a link between fluoride in drinking water and an increased risk of breast cancer. Fluoride is added to drinking water to prevent tooth decay.
Q19. Does chlorine in water increase breast cancer risk? Currently, there is insufficient evidence to conclude that chlorine in drinking water increases breast cancer risk, although there are some studies that claim it might do. Chlorine is added to water as a disinfectant.
Q20. Does drinking cow’s milk increase breast cancer risk? There is insufficient evidence to conclude that drinking cow’s milk increases breast cancer risk. Evidence from several meta-analyses suggests a diet high in milk may reduce pre-menopausal breast cancer risk and has no effect on risk for women after menopause. It should be noted that some observational studies have found a diet high in cow’s milk increases risk, some studies find the opposite, whilst many others conclude cow’s milk does not alter risk.
Dairy products are high in calcium and vitamin D, which are protective against breast cancer. Concerns stem from the fact that cow’s milk usually comes from pregnant cows and contains high levels of bovine hormones, including bovine oestrogen. Drinking cow’s milk containing high levels of this hormone increases levels of human insulin growth factor 1 (IGF-1), and women with higher levels of this growth factor have a slightly increased breast cancer risk. More research is needed to understand more clearly the impact cow’s milk has on breast cancer risk.
Q21. Can mammograms increase the risk of breast cancer? Mammograms deliver very low levels of ionising radiation, which will slightly increase breast cancer risk (estimated by the NHS to be 3-6 cancers per 10,000 women who are screened every 3 years from age 47 to 73).
Breast Cancer UK does not offer advice on mammography screening for breast cancer – individual participation is down to the choice of individuals.
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