Up to 10 percent of breast cancer cases are caused by mutations in tumor suppressor genes, including breast cancer susceptibility gene-1 (BRCA1) and breast cancer susceptibility gene-2 (BRCA2). Proteins made by these genes are used to repair damaged DNA. Defects in this process cause mutation carriers to have high lifetime risks of developing breast, ovarian and some other cancers.
Evidence suggests that the increased risks associated with BRCA mutations can be modified by lifestyle factors. For example, medium intensity physical activity has been found to be associated with a modest reduction in breast cancer risk for BRCA1 and BRCA2 carriers. In addition, there are some foods that have been found to protect against breast cancer in BRCA1 and/or BRCA2 carriers.

Foods that reduce risk of breast cancer in harmful BRCA carriers

The following foods have been found to be associated with reduced risk of breast cancer in BRCA1 and/or BRCA2 carriers or are rich sources of compounds that have been found to influence BRCA1 and/or BRCA2 expression in favorable ways:
Several studies have reported that heavy coffee consumption is associated with significantly reduced breast cancer risk among women with harmful BRCA1 or BRCA2 gene mutations. However, note that a 2013 study reported increased breast cancer risk for BRCA1 mutation carriers who were heavy coffee drinkers.

Foods to limit or avoid for BRCA mutation carriers

One study reported that consumption of flame-broiled fish was associated with increased risk of breast cancer in BRCA mutation carriers through its heterocyclic amine (HCA) content. Another study reported that consuming reheated cooking oil intensifies harmful BRCA1 mutations, apparently since repeated heating of oils produces reactive toxic intermediates that can lead to such mutations. This suggests that restaurant foods such as French fries that are cooked in oil that is used for many hours over a period of days should be avoided. Milk has also been linked to increased breast cancer risk in BRCA1 carriers.
The relationship between alcohol and breast cancer risk in BRCA mutation carriers is unclear. Not all studies have reported a harmful effect of alcohol consumption. However, two studies have reported that embryos with BRCA1 deficiencies are particularly susceptible to the carcinogenic effects of alcohol in animal models of breast cancer. Smoking during the pre-reproductive years appears to increase breast cancer risk for harmful BRCA mutation carriers.
Young women in general and BRCA1 mutation carriers in particular should avoid iron deficiency, since it has been linked to higher risk of breast cancer in these populations. However, note that meat consumption has been reported to preferentially increase breast cancer risk in BRCA2 carriers.

Potentially beneficial supplements for BRCA mutation carriers

It is best to obtain beneficial compounds by consuming food, if possible. However, supplements make sense if medically necessary or to make up for deficiencies that are difficult to correct through diet.
The following supplements generally have been found to be safe and beneficial for carriers of harmful BRCA mutations:
CoQ10 (if needed for heart health)100 to 400 mg/day
Fish oil (from wild-caught fish)1000 to 2000 mg/day
Vitamin D1000 to 2000 IU/day
Avoid taking supplements during the two days before, the day of, and the day after any chemotherapy treatment. There is some evidence that maintaining optimal levels of vitamin D could reduce the risk of triple negative breast cancer among BRCA1 carriers. It might make sense to be tested for deficiency in vitamin D and plan for follow up to determine if your level has reached a desirable level. Please consult your oncology team for advice concerning your situation and dosages.

Supplements to be avoided by BRCA mutation carriers

Attempting to take advantage of the apparent treatment effects of micronutrients and other dietary components by using supplements carries the risk of adverse and paradoxical effects, including promoting breast cancer growth and metastasis. When a beneficial micronutrient is administered at low doses by consuming food, it is likely to have subtle chemopreventive effects, whereas when the same micronutrient is administered at high doses, it is more likely to have pharmacological effects, with results that are not fully understood.
While supplements containing I3C, DIM, resveratrol, and genistein (all protective against BRCA-associated breast cancer) are readily available, a better strategy is to consume foods that contain these substances. Safe and effective dosages have not been determined for these compounds.

Bisphenol A (BPA) exposure

Bisphenol A (BPA), an endocrine disruptor, is suspected of increasing the risk of breast cancer. BPA has been found to stimulate mammary cell proliferation in BRCA1 mutant mice, leading to hyperplasia. This suggests that women with BRCA1 mutations might be particularly vulnerable to the cancer-promoting effects of BPA. BPA exposure can be limited by avoiding canned foods, canned sodas, and polycarbonate plastic bottles and food containers, which may be marked with a 7 or 3 recycling number in a triangle-shaped icon (normally found on the base).

Antiperspirants containing aluminum compounds

Most antiperspirant sprays, sticks, and roll-ons contain aluminum chlorohydrate or other aluminum salts designed to block the secretion of sweat. The aluminum in such preparations has been shown to enter through the skin in tiny amounts and to accumulate in breast tissue. Applying an antiperspirant to skin that is scraped, cut or irritated (such as may occur after shaving) can result in significantly higher exposures.
Aluminum has been demonstrated to cause DNA damage and to induce inflammatory responses within the breast. Aluminum salts found in antiperspirants were also shown in one study to reduce levels of (beneficial) BRCA1 mRNA and BRCA1 protein in normal breast epithelial cells. Levels of BRCA2 and other tumor suppressor genes (CHK1, CHK2, Rad51, and ATR) were also reduced. Given that aluminum appears to interfere with the functioning of tumor suppressor genes, BRCA mutation carriers should probably avoid using aluminum-containing antiperspirants.

Sources of information provided in this webpage

The food lists above, which are updated continually as new research becomes available, have been developed based solely on the results of academic studies. Clicking on any of the foods will take you to its webpage, which contains specific information concerning that food's relationship to breast cancer (including its overall ranking), as well as links to supporting studies.

Eat a wide variety of foods

It is important for BRCA1 and BRCA2 mutation carriers to eat a wide variety of the foods from our recommended food list and limit or avoid those on our avoid list, in addition to paying particular attention to the foods on the lists above. Please see our article on how to optimize your breast cancer diet for information on what to eat during all stages of treatment and recovery.
Below are links to 20 recent studies concerning this topic. For a more complete list of studies, please click on BRCA1 and BRCA2.