The role of physical activity and exercise in prevention

Breast cancer is the most common cancer in the UK. The second leading cause of cancer death in women, with one-in-seven women developing the disease at some stage in their lifetime. (1)

Once regarded as mainly a disease of inheritance, only about five to ten per cent of cancers are based on inherited genes (2). And only 3 per cent for breast cancer. (1)*.

What are some of the main risk factors?

Some risk factors you cannot change. For instance, the two most common risk factors for breast cancer are being a woman and ageing. Other factors you may have some control over. For example, a healthy lifestyle can reduce the possibility of developing breast cancer.

Concerning lifestyle studies, these include but are not limited to alcohol (3)(4), overweight and obesity, (5) diet (6), hormone replacement therapy (7)(8) and physical inactivity(9)

Risk Could be reduced by up to 25%

Over the past 20 years, extensive studies have examined the impact of physical activity and exercise on breast cancer. The evidence is pretty much incontrovertible: exercise can reduce your risk of breast cancer. The only question left to determine is by just how much.

For example, one 2014 meta-study looked at 73 individual studies worldwide. It concluded that women could reduce their risk of breast cancer by an average of 25% compared with inactive women. The associations were strongest for moderate-to-vigorous activity performed regularly, sustained over a lifetime for post-menopausal women and vigorous physical activity lowering the risk of premenopausal breast cancer (10)

The National Cancer Institute (part of the National Institutes of Health within the United States) also did a comprehensive meta-study of breast cancer prevention and concluded, based on a survey of 31 different studies, that the average breast cancer risk reduction rate is 12%. That figure is for all women, both premenopausal and postmenopausal. (11)

Women who increase their physical activity after menopause also have a lower risk of breast cancer than inactive women. (12)(13)

Finally, the Susan G. Komen Foundation, one of the leading organisations helping to fight breast cancer, says that regular exercise can lower your breast cancer risk by anywhere from 10-20% based on a review of the research. (14)

Thus, if you consider all these physical activity studies, the lifetime risk of breast cancer could be reduced considerably, in some cases by up to 25%.

How does physical activity help prevent breast cancer?

While medical researchers are pretty much unanimous that physical activity helps to prevent breast cancer, less is known about the mechanism that makes it possible. One prevailing theory is that physical activity helps to lower the level of circulating hormones (especially insulin and oestrogen) and related growth factors and reduces inflammation, which can contribute to cancer development and progression. (10)

Another common theory is that physical activity works indirectly by reducing overweight and obesity. By helping to keep your weight under control, especially around the middle, physical activity significantly lowers the risk factors linked to chronic diseases and cancer. [15]  Physical activity also has a protective effect, independent of its impact on body weight. In other words, it helps even if you are not losing weight.

And there are still other ways that physical activity can reduce your risk of breast cancer. The National Cancer Institute (NCI) notes that exercise also boosts your immune system. The stronger your immune system, the more powerful it is when fighting cancer cells. The NCI also notes that regular physical activity can reduce body inflammation, which has also been linked to chronic disease and cancer. And finally, the NCI notes that physical activity might lessen your exposure to carcinogens (i.e. cancer-causing agents) by reducing the time it takes food to travel through your digestive system. (16)

How much physical activity do you need?

Guidance from the Chief Medical Office (CMO) in the UK recommends 150 minutes of moderate physical activity per week. That works out to two and one-half hours of exercise per week. You can exercise for even less time – just 75 minutes per week – if the level of exercise intensity is vigorous. And, if the level of exercise falls somewhere between moderate and vigorous, then you can extrapolate that you will need somewhere between 75 and 150 minutes per week. (17) Those numbers are backed up by Cancer Research UK, which uses the 150 minutes figure as an important baseline number.

It’s important to recognise also that exercise, while a powerful tool, will not be enough to prevent breast cancer entirely. Exercise is all about reducing your risk factors. Make sure you find something fun and engaging to enjoy yourself.

Written by Darryl Edwards, a Movement Coach, Natural Lifestyle Educator, nutritionist, and creator of the Primal Play Method developed to inspire others to make activity fun while getting healthier, fitter and stronger. Try a fun activity today and get active – Fancy a game of tag?

References:

(1)  – World Cancer Research Fund. Breast Cancer. 2017, https://www.wcrf-uk.org/uk/preventing-cancer/cancer-types/breast-cancer

*note: 3% refer to breast cancers caused by single inherited gene mutations such as BRCA1

(2) https://www.wcrf-uk.org/uk/preventing-cancer/what-can-increase-your-risk-cancer/inherited-genes-family-history-and-cancer

(3) Dorgan JF, Baer DJ, Albert PS, Judd JT, Brown ED, Corle DK. “Serum hormones and the alcohol-breast cancer association in postmenopausal women.”, J Natl Cancer Inst . 2001;939:710–715., – https://www.ncbi.nlm.nih.gov/pubmed/11333294

(4)  Smith-Warner SA, Spiegelman D, Yaun SSet al. , “Alcohol and breast cancer in women: A pooled analysis of cohort studies.”,JAMA . 1998;2797:535–540., – https://www.ncbi.nlm.nih.gov/pubmed/9480365

(5) Fortner RT, Katzke V, Kuhn T, Kaaks R., “Obesity and breast cancer.”, Recent Results Cancer Res . 2016;208:43–65., – https://www.ncbi.nlm.nih.gov/pubmed/27909901

(6) Castello A, Martin M, Ruiz Aet al. , “Lower breast cancer risk among women following the World Cancer Research Fund and American Institute for Cancer Research Lifestyle Recommendations: EpiGEICAM Case-Control Study.”, PLoS One . 2015;105:e0126096., – https://www.ncbi.nlm.nih.gov/pubmed/25978407

(7) Beral V, Million Women Study C. “Breast cancer and hormone-replacement therapy in the Million Women Study.”, Lancet . 2003;3629382:419–427., https://www.ncbi.nlm.nih.gov/pubmed/12927427

(8) Chlebowski RT, Anderson GL, Gass Met al., “Estrogen plus progestin and breast cancer incidence and mortality in postmenopausal women. JAMA . 2010;30415:1684–1692., https://www.ncbi.nlm.nih.gov/pubmed/20959578

(9) Friedenreich CM, Cust AE. “Physical activity and breast cancer risk: Impact of timing, type and dose of activity and population subgroup effects.”, Br J Sports Med . 2008;428:636–647.,  https://www.ncbi.nlm.nih.gov/pubmed/18487249

(10) Lynch BM, Neilson HK, Friedenreich CM , “Physical activity and breast cancer prevention.”, Recent Results Cancer Res. 2011; 186:13-42., https://www.ncbi.nlm.nih.gov/pubmed/21113759/

(11) Wu Y, Zhang D, Kang S., “Physical activity and risk of breast cancer: a meta-analysis of prospective studies.”, Breast Cancer Research and Treatment 2013; 137(3):869-882., https://www.ncbi.nlm.nih.gov/pubmed/25978407

(12) Fournier A, Dos Santos G, Guillas G, et al., “Recent recreational physical activity and breast cancer risk in postmenopausal women in the E3N cohort.”, Cancer Epidemiology, Biomarkers & Prevention 2014; 23(9):1893-1902., https://www.ncbi.nlm.nih.gov/pubmed/20975025

(13) Eliassen AH, Hankinson SE, Rosner B, Holmes MD, Willett WC., “Physical activity and risk of breast cancer among postmenopausal women.”, Archives of Internal Medicine 2010; 170(19):1758-1764., https://www.ncbi.nlm.nih.gov/pubmed/20975025

(14) https://ww5.komen.org/BreastCancer/Table4Recreationalphysicalactivityandbreastcancerrisk.html

(15)  Shaw KA, Gennat HC, O’Rourke P, Del Mar C, “Exercise for overweight or obesity.”, Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD003817. DOI: 10.1002/14651858.CD003817.pub3 – https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD003817.pub3/abstract

(16) Moore SC, et al., “Leisure-time physical activity and risk of 26 types of cancer in 1.44 million adults.”, JAMA Internal Medicine. May 16, 2016. DOI:10.1001/jamainternmed.2016.1548. – https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2521826

(17) https://www.gov.uk/government/publications/uk-physical-activity-guidelines