3 years ago
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)*.
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, living 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)
Over the past 20 years, extensive studies have been done, examining 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 that is left is to determine is by just how much.
For example, one 2014 meta-study looked at 73 individual studies from around the world and 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 women who are inactive. (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 take all these physical activity studies into account, the lifetime risk of breast cancer could be reduced considerably, in some cases by up to 25%.
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 plays a significant role in lowering the risk factors linked to risk of chronic diseases and cancer.  The physical activity itself also has a protective effect, which is 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 be used to reduce your risk of breast cancer. The National Cancer Institute (NCI) notes that exercise is also very good at boosting your immune system. The stronger your immune system, the more powerful it is when it comes to 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 amount of time that it takes food to travel through your digestive system. (16)
Guidance from the Chief Medical Office (CMO) in the UK recommends 150 minutes of moderate physical activity per week. That works out to a total of 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 also uses the 150 minutes figure as an important baseline number.
It’s important to recognise also that exercise, while a powerful tool, is not going to 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 while doing so.
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 in the process. Try a fun activity today and get active – Fancy a game of tag?
(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
(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
(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
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