Some factors that determine your personal risk of breast cancer are beyond your control, such as age and family history. But diet is one of several breast cancer risk factors you do have the power to change, and it can play a pivotal role in reducing your risk of the disease.
About 30 percent of postmenopausal breast cancer diagnoses are linked to modifiable risk factors such as diet, according to the American Cancer Society. Other studies have shown that as many as 50 to 70 percent of breast cancers can be prevented depending on when people make healthy lifestyle changes. And there is even some research suggesting that following healthy eating habits may reduce the risk of cancer recurrence and death among breast cancer patients.
Scientists are still unraveling the relationship between breast cancer and diet, so there is no agreed-upon “breast cancer diet” shown to prevent the disease or improve outcomes in those who have it. But so far, research indicates that many of the foods and nutrients known to support overall health, such as vegetables and fiber, are also key for breast health.
Diet appears to influence the risk of breast cancer in several ways. For one, being overweight or obese is a well-established risk factor for breast cancer, and eating healthfully plays an essential role in helping you lose weight (if needed) and keep your weight stable. Excess body fat has been linked to a higher risk of breast cancer in postmenopausal women due to its effects on inflammation, hormone levels, factors that regulate cell growth, and others.
Fortunately, you can decrease your risk by losing weight and maintaining the loss. A 2020 study conducted by BCRF investigator Dr. Walter Willett showed that women over 50 who lost 10 or more pounds and sustained it could reduce their future breast cancer risk by 32 percent.
Eating a balanced, healthy diet also has other benefits, too. A healthy lifestyle is linked with lower levels of inflammation, and studies suggest that certain nutrients, vitamins, and compounds have anti-cancer properties that may help lower your risk of breast cancer. One well-known example is antioxidants, which are naturally occurring substances found in fruits, vegetables, and other plant-based foods. Antioxidants neutralize free radicals—unstable molecules than can damage cells’ DNA, thereby supporting the development and progression of breast cancer. Examples of antioxidants include vitamins C (found in citrus and red and green peppers), vitamin E (almonds, hazelnuts), polyphenols (broccoli, olive oil, oats), and carotenoids (spinach, carrots, mango).
Fiber may also play a significant role in breast cancer prevention. A review of studies published in the journal Cancer found that women who consumed the highest amounts of fiber were eight percent less likely to develop the disease compared to those who ate the least. That may be due to fiber’s ability to control blood sugar and lower levels of estrogen.
Eating more fiber may also help prevent breast cancer by influencing the makeup of your gut microbiome—the balance of good and bad microorganisms that reside in the gastrointestinal tract. Studies suggest that the microbiome may impact the risk of breast cancer by altering estrogen metabolism. Dr. Willett is currently using questionnaires and blood and fecal samples from women whose lifestyle and dietary choices have been followed for decades to study the microbiome’s role in breast cancer risk and prevention.
Antioxidants and fiber aren’t the only compounds and nutrients that may reduce your risk of breast cancer. Studies suggest that vitamin D, calcium, and polyunsaturated fatty acids (PUFAs) such as omega-3 fatty acids may also have protective effects. And soy foods such as tofu and edamame, once thought to increase the risk of breast cancer, appear to lower it.
Many of nutrients and compounds that could help prevent breast cancer may also benefit those who have the disease, though more research is needed to confirm the links. A review of research published in the International Journal of Environmental and Public Health showed that breast cancer patients who adopted a healthy diet—one with high intakes of fruits, vegetables, and whole grains, and limited intakes of red and processed meats and saturated fats—post diagnosis can reduce mortality from all causes, including breast cancer.
Combining good breast cancer nutrition with exercise may also have a significant impact on outcomes. A recent study conducted by BCRF researcher Dr. Melinda Irwin showed that following an exercise program and a diet high in fruits, vegetables, and fiber and low in sugar and processed foods was associated with a greater pathological complete response (pCR) in patients with hormone receptor (HR)-positive/HER2-negative and triple-negative breast cancer undergoing presurgical chemotherapy. Exercise and a healthy diet may improve pCR by reducing inflammation and improving immune response.
While there are no “superfoods” that lower your likelihood of developing breast cancer, studies show that following a mostly plant-based diet may have a protective effect, especially among post-menopausal women. Many studies have focused on the Mediterranean diet, a pattern of eating that emphasizes whole, minimally processed foods. A 2017 study published in the International Journal of Cancer found that post-menopausal, estrogen receptor (ER)–negative breast cancer—a subtype with a poor prognosis—was 40 percent less prevalent in those who adhered closely to the Mediterranean diet.
Key components of the Mediterranean diet include:
You may associate wine with the Mediterranean diet; however, the researchers excluded it from the study because alcohol is linked to a higher risk of breast cancer.
In general, it’s best to avoid the typical western-style diet many Americans follow, which is high in processed grains, processed meats (bacon, hot dogs), and red meats—all foods associated with increased rates of breast risk and progression. Nutrients and foods to avoid with breast cancer include:
Saturated fat and trans fats. Foods high in saturated fat, particularly high-fat dairy products such as butter and cheese,may increase breast cancer mortality. Other foods high in saturated fat include beef, lamb, pork, poultry (especially with skin); lard; coconut oil and palm oil; and many baked and fried foods (such as fast food). Trans fat, found in fried foods and baked goods, should also be avoided: Studies found that intake of trans fats after diagnosis was associated with a 45 percent increased risk of breast cancer–specific mortality and 78 percent all-cause mortality.
Alcohol. Experts know that drinking any type of alcohol (beer, wine, liquor) raises the risk of breast cancer, but alcohol may also have detrimental effects on breast cancer patients. Studies of drinking and its impact on survivorship have yielded mixed results, but preliminary research suggests a connection between alcohol intake and poorer outcomes in patients who are postmenopausal or who have ER-positive breast cancer.
Foods high in added sugar. The rumor that sugar “feeds” cancer isn’t true, but it is wise to limit foods high in added sugars like high-fructose corn syrup, because they’re typically high in calories and contribute to weight gain, insulin resistance, and inflammation. Obvious sources of added sugar include desserts (candy, cookies, pies, cake), juice, and soda. However, added sugar also lurks in foods you might not suspect, such as pasta sauce, salad dressing, dried fruit, and condiments such as ketchup.
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