Breast cancer risk: genetics vs. lifestyle
Angelina Jolie’s choice to undergo a preventive double mastectomy because of a family history of breast cancer and a mutation in the BRCA1 gene made news and raised important questions. Complex medical decisions like these are personal and must be made on an individual basis. The appearance of this story and subsequent debate in the global media, however, brings up critical issues about the relative contributions of genetics and lifestyle to breast cancer risk. Also it begs the question, if you are indeed genetically susceptible to breast cancer, can you reduce this risk through nutrition?
The BRCA1 and BRCA2 genes are tumor suppressors.1 Having one of several known mutations in one of these genes is known to impair their function and produce a predisposition for breast cancer and several other cancers. There are mutations in other genes that also increase risk; however the majority of hereditary breast cancer cases are attributed to BRCA1 and BRCA2 mutations. These mutations produce a substantial increase in breast cancer risk. About 12 percent of women in the general population will develop breast cancer throughout their lifetimes, but about 60 percent of women who carry a BRCA mutation will develop breast cancer;2 women with a family history and a BRCA mutation could have a risk of breast cancer as high as 87 percent.3 This is frightening, but keep in mind that most breast cancers are not due to these mutations. The percentage of breast cancer cases that are due to BRCA1 mutations is estimated at 3.5-6.2 percent and 2.1-3.4 percent for BRCA2 mutations.3
Breast cancer is a complex disease with many contributing factors. Even those with a genetic issue can dramatically reduce their risk of breast cancer and other cancers through strong dietary decisions. Natural plant foods contain a huge quantity and variety of phytochemicals, micronutrients with a variety of anti-cancer effects: anti-estrogenic, anti-proliferative, pro-apoptotic, anti-angiogenic, antioxidant and anti-inflammatory effects. All of these different functions act synergistically to prevent the development of cancers, regardless of a person’s genotype.
For example, studies have demonstrated that vegetable and fruit consumption or an overall healthful diet is associated with decreased breast cancer risk, even in carriers of BRCA mutations.6,7 The fact that not every woman who has these mutations gets breast cancer suggests that environmental factors can have a preventive effect. An important study demonstrated that higher cruciferous vegetable intake cut risk in half for women with a breast cancer-associated genetic mutation.8,9 This significant reduction in risk was only from the green vegetables at modest intake, it was not the the entire Nutritarian diet – a diet consisting primarily of nutrient-rich foods - designed to maximize protection with all the anti-cancer foods present simultaneously. So even with heightened genetic risk, healthful foods are significantly protective. Since several populations around the world 25 years ago had only about one-tenth of the breast cancer rates that we had in the U.S.,10-12 it is clear that even in the context of increased genetic risk, diet and lifestyle trump genetics.
Regardless of family history, genetic mutation, or even double mastectomy, a Nutritarian diet is essential for reducing cancer risk.
A Nutritarian diet consists of the following key foods referred to as G-BOMBS (Greens, Beans, Onions, Mushrooms, Berries, Seeds). Unfortunately because every cancer prevention study focuses only on one variable, not the synergistic benefits that add up from the entire Nutritarian lifestyle: isothiocyanates from cruciferous vegetables13, organosulfur compounds from onions and garlic, aromatase inhibitors from mushrooms, flavonoids from berries, lignans from flax, chia and sesame seeds, angiogenesis inhibitors from beans, anti-estrogenic effects of fiber, plus the protective effects of exercise have yet to be calculated. That said, each of these factors has been shown to be powerfully protective; for example, one interesting study on lignans followed women for up to 10 years and found a 71 percent reduced risk of breast cancer mortality in women with the highest lignan intake.14 This demonstrates dramatic anti-cancer potential from the Nutritarian approach, because this study was performed on women late in life who already had a diagnosis of breast cancer, and their lignan intake was only minimal. In other words, even more significant protection can be assumed when these changes are much more significant and started earlier in life before breast cancer occurs.
An important point this news story brought up was empowerment, and I want to emphasize that when faced with simple, every day choices – what to have for breakfast, lunch and dinner – all women have the power to achieve substantial protection against breast cancer. Many women can’t afford to get genetic testing, or a preventive mastectomy if they are positive for a mutation, but all women can’t afford NOT to eat a Nutritarian diet for their hearts, their brains, their breasts and their peace of mind.
1. Fan S, Meng Q, Auborn K, et al: BRCA1 and BRCA2 as molecular targets for phytochemicals indole-3-carbinol and genistein in breast and prostate cancer cells. Br J Cancer 2006;94:407-426.
2. BRCA1 and BRCA2: Cancer Risk and Genetic Testing. National Cancer Institute. http://www.cancer.gov/cancertopics/factsheet/Risk/BRCA. Accessed
3. Robson ME: Clinical considerations in the management of individuals at risk for hereditary breast and ovarian cancer. Cancer Control 2002;9:457-465.
4. Bosviel R, Durif J, Dechelotte P, et al: Epigenetic modulation of BRCA1 and BRCA2 gene expression by equol in breast cancer cell lines. Br J Nutr 2012;108:1187-1193.
5. Fustier P, Le Corre L, Chalabi N, et al: Resveratrol increases BRCA1 and BRCA2 mRNA expression in breast tumour cell lines. Br J Cancer 2003;89:168-172.
6. Ghadirian P, Narod S, Fafard E, et al: Breast cancer risk in relation to the joint effect of BRCA mutations and diet diversity. Breast Cancer Res Treat 2009;117:417-422.
7. Nkondjock A, Ghadirian P: Diet quality and BRCA-associated breast cancer risk. Breast Cancer Res Treat 2007;103:361-369.
8. Lee SA, Fowke JH, Lu W, et al: Cruciferous vegetables, the GSTP1 Ile105Val genetic polymorphism, and breast cancer risk. Am J Clin Nutr 2008;87:753-760.
9. Huang MY, Wang YH, Chen FM, et al: Multiple Genetic Polymorphisms of GSTP1 313AG, MDR1 3435CC, and MTHFR 677CC highly correlated with early relapse of breast cancer patients in Taiwan. Ann Surg Oncol 2008;15:872-880.
10. International Agency for Research on Cancer, World Health Organization. CI5plus: Cancer Incidence in Five Continents Annual Dataset [http://ci5.iarc.fr/CI5plus/ci5plus.htm]
11. Ahn YO, Park BJ, Yoo KY, et al: Incidence estimation of female breast cancer among Koreans. J Korean Med Sci 1994;9:328-334.
12. Bah E, Hall AJ, Inskip HM: The first 2 years of the Gambian National Cancer Registry. Br J Cancer 1990;62:647-650.
13. Liu X, Lv K: Cruciferous vegetables intake is inversely associated with risk of breast cancer: A meta-analysis. Breast 2012.
14. McCann SE, Thompson LU, Nie J, et al: Dietary lignan intakes in relation to survival among women with breast cancer: the Western New York Exposures and Breast Cancer (WEB) Study. Breast Cancer Res Treat 2010;122:229-235.