October has been coined “Breast Cancer Awareness Month”, in an attempt to increase not only awareness, but encourage breast cancer screening, and raise money for a cure. Unfortunately, not much effort is put into educating women (and men) about prevention, which is a shame considering that a healthy lifestyle can significantly lower one’s risk of developing this terrible disease (1-2).
Although genetics can play a role, maintaining a healthy body weight, avoiding alcohol and tobacco, breastfeeding (for women), and regular exercise are all lifestyle interventions that can lower one’s risk of breast cancer. When it comes to diet and breast cancer, consuming a high-fiber, plant-based diet centered on whole grains, beans/legumes, fruit, and vegetables appears most favorable (3-8). This advice is echoed by the American Institute for Cancer Research, whose top diet strategy for cancer prevention is to eat a plant-based diet.
In addition to a plant-based diet and overall healthy lifestyle, there are a handful of foods that appear especially protective against breast cancer. The following foods should be consumed on a regular basis for optimal breast cancer protection, and to improve outcomes in those who may already carry a diagnosis.
Soy is the most controversial food when it comes to breast cancer. This is because it’s rich in phytoestrogens, which are naturally-occurring plant compounds that are structurally and/or functionally similar to human estrogen. Since high estrogen levels are associated with an increased risk of developing breast cancer, the thought was that consuming a diet rich in phytoestrogens may elevate one’s risk in a similar manner. This theory, however, is just that, a theory. The overall evidence on soy consumption and breast cancer suggests the exact opposite—that soy can protect against breast cancer. It appears that the phytoestrogens in soy can inhibit the action of human estrogen by competing for the same binding sites throughout the body. Additionally, other compounds in soy may have anti-cancer properties and could also be playing a role. Regardless of the mechanisms, here’s what the data on soy and breast cancer show:
In terms of breast cancer prevention, higher soy intake is associated with a lower risk of developing breast cancer (9-14). This association is stronger in Asian populations who tend to eat more soy, but is maintained to a lesser extent in Western populations who tend to eat less soy (10). Soy appears especially protective when consumed before and during puberty, as it is thought to favorably alter genes that may influence future cancer risk (15). Studies overwhelmingly show that higher soy consumption during childhood and adolescence is associated with lower rates of breast cancer later in life (16-18). This may explain why Asian populations, who consume more soy throughout their life, have lower rates of breast cancer compared to Western populations. In fact, women living on the island of Okinawa, Japan, who consume the traditional diet centered on sweet potatoes, soy, rice, and vegetables, have the longest life expectancy in the world, and extremely low rates of breast cancer.
In addition to helping prevent breast cancer, soy consumption may improve survival and reduce recurrence in women who already carry a diagnosis. Study after study have come to the same conclusion, that women with higher soy intakes have lower mortality rates and lower recurrence rates, compared to women who consume little or no soy (19-27).
These studies look at whole soy consumption, not soy powders, supplements, or extracts. Products like these, because they are in an unnatural state, may not offer the same benefits as whole soy foods and could potentially be harmful. Avoid these products and stick with whole or minimally processed soy foods, such as soy beans, edamame, tofu, tempeh, and soy milk. Check out my Vegan Soul Bowl, Farmers’ Market Tofu Scramble, Aloha Vegan Poke Bowl, or Vegan Lasagna for tasty ways to include soy in your diet.
Similar to soy, flaxseeds are rich in phytoestrogens, particularly a specific class called lignans. When studied, both flaxseed and lignin consumption is associated with a lower risk of developing breast cancer and appears to improve survival in those who already have the disease (28-32). One randomized double-blind placebo-controlled study even found that daily intake of a flaxseed-containing muffin (versus a muffin without flaxseed) significantly reduced tumor growth in newly diagnosed breast cancer patients (33).
Flaxseeds are best consumed ground, because whole seeds tend to pass right through us and are not absorbed. A tablespoon or two of ground flaxseed can be added to oatmeal, smoothies, or mixed into sauces. When baking, a “flax-egg” can be used as a healthier alternative to real eggs. For every egg the recipe calls for, simply mix one tablespoon of ground flaxseed in three tablespoons of water. Let the mixture sit for a few minutes—as it will thicken to the consistency of a whisked egg—and bake away.
Mushrooms are unique in that they are neither plant nor animal, but belong to the entirely different biological kingdom of fungi (along with yeast and mold). Because they are biologically unique, they also are nutritionally unique. When consumed, edible mushrooms offer a wide range of health-promoting benefits. One of those benefits is the ability to inhibit an enzyme called aromatase.
Aromatase plays a key role in the body’s production of estrogen – a hormone that, when made in excess, can promote breast cancer. Mushrooms have been shown to inhibit aromatase activity in laboratory studies (34). They have also been shown to inhibit breast cancer cell growth in both petri dishes and mice (35-37). Population-based human studies support these lab findings. Compared to women with breast cancer, women without it tend to consume more mushrooms (38-40). A 2014 meta-analysis of observational studies confirmed that mushroom intake is associated with a lower risk of breast cancer (41). There’s also some research to suggest that mushroom consumption may boost the effectiveness of conventional breast cancer therapies (42).
Many of these studies used mushroom varieties that you can find at any grocery store, such as white button, cremini, portabella, oyster, and maitake. The data also suggests that we don’t need to eat a whole carton of mushrooms every day to see a benefit; consuming an average of one mushroom a day can be beneficial. I usually buy a carton of mushrooms once a week and add them to various recipes. My favorite dishes to add them, include: pasta with marinara, vegetable stir-fry’s, vegan poke bowl, tofu breakfast scrambles, stuffed acorn squash, vegan pizza, and even veggie burgers.
If you walk through the produce department at your local grocery store, you will see a rainbow of colors. These colors represent the various pigments found in plants. One of these pigments is beta-carotene, which is responsible for the bright orange color found in many fruits and vegetables. Studies show that women who consume a diet rich in beta-carotene have a lower risk of developing breast cancer (43-49). These studies can’t prove cause and effect, so beta-carotene intake could just be a reflection of high fruit and vegetable intake. It may also be some other nutrient in orange produce that is protective against breast cancer. But, regardless of the mechanisms, consuming foods rich in beta-carotene appears to lower one’s risk of developing breast cancer. The same cannot be said for beta-carotene supplements, which should be avoided.
Pound for pound, the following foods are the best sources of beta-carotene: orange sweet potatoes, orange carrots, red/orange peppers, pumpkin, and other winter squash, such as butternut, acorn, and hubbard. Most dark leafy greens are also rich in beta-carotene (despite not being orange), so include them in your diet as well. Fruit such as cantaloupe, apricots, and papaya are also good sources. The following recipes feature foods rich in beta-carotene: Creamy Butternut Squash Pasta with Broccoli, Pumpkin Spice Smoothie, Vegan Soul Bowl, Sweet Potato and Black Bean Enchilada, Revitalizing Tropical Smoothie, and African Peanut Soup.
Benjamin Franklin was spot-on when he said that an ounce of prevention is worth a pound of cure. As we continue looking for better treatment options and a cure, we should also focus our efforts on prevention. Maintaining a healthy body weight, avoiding alcohol and tobacco, breastfeeding (for women), regular exercise, and a high-fiber, plant-based diet can be our first line defense against this disease. In addition, soy foods, flaxseeds, mushrooms, and orange produce should be consumed on a regular basis.
Please share this information with family, friends, and loved ones, as it’s never too early, or too late, to improve your health.
Peace, love, health
- Is concordance with World Cancer Research Fund/American Institute for Cancer Research guidelines for cancer prevention related to subsequent risk of cancer? Results from the EPIC study
- Healthy lifestyle on the risk of breast cancer.
- Dietary fiber and breast cancer risk: a systematic review and meta-analysis of prospective studies.
- Dietary fiber intake and risk of breast cancer by menopausal and estrogen receptor status.
- Dietary fiber intake and risk of breast cancer: a meta-analysis of prospective cohort studies.
- Dietary fiber intake and risk of breast cancer in postmenopausal women: the National Institutes of Health-AARP Diet and Health Study.
- Effect of dietary fiber intake on breast cancer risk according to estrogen and progesterone receptor status.
- Vegetarian diets and the incidence of cancer in a low-risk population.
- Association between Soy Isoflavone Intake and Breast Cancer Risk for Pre- and Post-Menopausal Women: A Meta-Analysis of Epidemiological Studies
- Intake of Soy Isoflavones Reduces Breast Cancer Incidence among Women in North America
- Is soy consumption good or bad for the breast?
- Epidemiology of soy exposures and breast cancer risk.
- Meta-analysis of soy intake and breast cancer risk.
- Soy isoflavones consumption and risk of breast cancer incidence or recurrence: a meta-analysis of prospective studies.
- Childhood soy intake and breast cancer risk in Asian American women.
- Adolescent and adult soy intake and risk of breast cancer in Asian-Americans.
- Soyfood intake during adolescence and subsequent risk of breast cancer among Chinese women.
- Soy food intake after diagnosis of breast cancer and survival: an in-depth analysis of combined evidence from cohort studies of US and Chinese women.
- Dietary isoflavone intake and all-cause mortality in breast cancer survivors: The Breast Cancer Family Registry
- Positive effects of soy isoflavone food on survival of breast cancer patients in China.
- Effect of soy isoflavones on breast cancer recurrence and death for patients receiving adjuvant endocrine therapy.
- Study on soy isoflavone consumption and risk of breast cancer and survival.
- Soy food consumption and breast cancer prognosis.
- Post-diagnosis soy food intake and breast cancer survival: a meta-analysis of cohort studies.
- Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study.
- Soy food intake and breast cancer survival.
- Dietary lignan intakes in relation to survival among women with breast cancer: the Western New York Exposures and Breast Cancer (WEB) Study.
- Lignans and breast cancer risk in pre- and post-menopausal women: meta-analyses of observational studies
- Meta-analyses of lignans and enterolignans in relation to breast cancer risk.
- Consumption of flaxseed, a rich source of lignans, is associated with reduced breast cancer risk.
- Flax and Breast Cancer: A Systematic Review.
- Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer.
- White button mushroom phytochemicals inhibit aromatase activity and breast cancer cell proliferation.
- Commonly consumed and specialty dietary mushrooms reduce cellular proliferation in MCF-7 human breast cancer cells.
- Anti-aromatase activity of phytochemicals in white button mushrooms (Agaricus bisporus).
- Inhibition of growth and induction of apoptosis in human cancer cell lines by an ethyl acetate fraction from shiitake mushrooms.
- Dietary intakes of mushrooms and green tea combine to reduce the risk of breast cancer in Chinese women.
- A case-control study on the dietary intake of mushrooms and breast cancer risk among Korean women.
- Dietary mushroom intake and the risk of breast cancer based on hormone receptor status.
- Dietary mushroom intake may reduce the risk of breast cancer: evidence from a meta-analysis of observational studies.
- The effects of dietary supplementation with Agaricales mushrooms and other medicinal fungi on breast cancer: evidence-based medicine.
- Beta-carotene intake and risk of postmenopausal breast cancer.
- Dietary carotenoids and risk of breast cancer in Chinese women.
- Premenopausal breast cancer risk and intake of vegetables, fruits, and related nutrients.
- Serum carotenoids and breast cancer.
- Plasma carotenoids and risk of breast cancer over 20 y of follow-up
- Plasma carotenoids, retinol, and tocopherols and risk of breast cancer.
- Prospective study of carotenoids, tocopherols, and retinoid concentrations and the risk of breast cancer.