Updated: Jul 5
I'm often asked as a breast cancer dietitian, I had a breast cancer diagnosis, what should I eat? Do I need to go vegetarian—or vegan— to lower my risk of hormone-related cancers and recurrence? And what about low fat—how low should I go?
Hold on to your chocolate croissant. Because my answer is this: Find a pattern of eating you enjoy, which also happens to make you feel better, stronger, and prevent disease. Food should not be yet another source of stress for survivors.
Nutrition studies are notoriously difficult to conduct. You can't lock people in a room for weeks and ask them to only eat certain foods (although that has been done). The evidence is mixed when it comes to hormone-related cancers, including breast, endometrium, and ovarian cancers. Some studies point to no evidence or a mild effect, while others show a definite impact, but only on a specific hormone receptor status. Other studies show an effect, depending on the age of diagnosis or the diet before diagnosis.
But there are recent studies with preliminary results on nutrition and specific types of breast cancer:
Eating vegetables are associated with lower risk of the more aggressive estrogen receptor negative (ER–) tumors.
Close to one-third of ER– breast cancer, and a small percentage of total breast cancer, could be avoided with higher adherence to a Mediterranean-type diet. The Mediterranean diet is filled with plant foods.
Eating non-starchy vegetables have more of an effect on reducing ER– breast cancers than other types of breast cancers. Non-starchy vegetables are beets, parsnips, turnips, spinach and lettuce, and onions, garlic, and leeks.
As far as age, younger women eating fewer plant foods in adolescence and early adulthood may lead to a higher risk of premenopausal breast cancer. In postmenopausal women, dietary fiber found in fruits may have a role in preventing breast cancer and recurrence, as fiber removes excess estrogen from the body.
The evidence is very strong that eating a spectrum of fruits and vegetables protects your heart and brain. But do these plant foods also lower your risk of breast cancer? The very same foods that are good for the heart and brain—and your bones—also work to reduce cancer risk and chronic disease.
As a dietitian, I know that more fruits and vegetables lower inflammation, enabling the body to reduce cancer risk. Researchers analyzed 13 population studies, and found that women who ate a higher amount of cruciferous vegetables had a 15 percent lower risk of breast cancer, compared to those who ate the least. This class of vegetables includes broccoli, brussels sprouts, cabbage, watercress, and kale.
Here are some answers about eating to reduce cancer risk:
What about specific foods? Vegetables with orange, yellow, and green pigments have carotenoids, and women with higher levels of this phytochemical have lower rates of all breast cancers. Foods high in dietary calcium are associated with a decreased risk of premenopausal breast cancer. You can find calcium in plant foods such as fortified plant-milks and tofu; green vegetables such as, broccoli, bok choy, and Napa cabbage; fruits such as dried figs; almond butter and almonds; and tahini sesame paste.
How many plant foods are enough? Five to seven servings a day are the most protective. Studies don't show an increased benefit above that amount. Women who ate more than five and a half servings of fruits and vegetables had an 11 percent lower risk of breast cancer than those who ate two and a half servings. A serving is one cup of leafy greens, half cup raw or cooked vegetables, or a half cup of chopped or cooked fruits.
How do cancer survivors or those newly diagnosed make sense of all the nutrition and cancer evidence? Most of the studies point to a Mediterranean type diet, with anti-inflammatory, high fiber, and colorful plant foods, as the most likely to reduce cancer. Moreover, the overall pattern of eating, with lots of diverse foods, are more protective than any one food—not that mushrooms or broccoli aren't good for you. A wide array of plant foods are the key to a strong microbiome, an environment hostile to cancer growths.
What about my weight? A diet poor in nutrients increased breast cancer by 10 percent—and this is important—regardless of a women's weight.
Does exercise make a difference? This is where we have the strongest evidence to date. Exercise combined with diet increases the years of survival after breast cancer. Women who ate five vegetable and fruit servings a day and moved daily, had a higher 10-year survival rate than those who did not accomplish these lifestyle changes.
Finally, the most recent research points to a lower fat pattern of eating to reduce the risk of dying from breast cancer. The study is based on data from the federally funded Women’s Health Initiative (WHI). In this clinical trial, 48,835 postmenopausal women age 50-79, with no previous history of breast cancer, were asked to modify their diet from 1993 to 1998. (Previous studies were mixed.) Note that this study was done during the era when low fat diets were recommended.
How lowfat did these women achieve? Many of the women studied had previously eaten 32% of their calories from fat. They were asked to reduce it to 20%, but most ended up eating a diet with 25% or less, and the majority did not reach the goal. Thus, this was a lower fat study—not necessarily a low-fat diet. These fat calories are in line with current dietary guidelines.
Women were also asked to increase their intake of fruits, vegetables, and whole grains, and meet with dietitians. So, although this study shows the way we eat does have an impact on disease, it's unclear whether benefits were accrued from extra servings of health-promoting foods, or only from eating lower fat.
Going vegetarian may not change a strong hereditary BRCA-related cancer risk. But discovering new plant foods empowers you to become a strong thriver. A heavily plant-based diet prevents the diseases survivors are more at risk for, including heart disease and bone loss.
Eating well prevents the risk factors that lead to cardiovascular disease, such as high blood pressure, diabetes, and unhealthy levels of fat in the blood. Plant foods help with mild depression, better mood, cognition, and the ability to better withstand cancer treatment.
A note on supplements: Aside from correcting nutritional deficiencies, you can't rely on supplements to make up for dietary shortfalls. Studies show they don't prevent cancer, and taking more vitamins and minerals than you need can be harmful. Fiber is usually missing from blended drinks, so don't rely on juices and clear smoothies to up your intake.
Finally, live your best life while trying not to give in to food fears, or use restrictive dieting methods, a common habit in cancer survivors. This is not how to take care of your body, because yo-yo dieting actually increases the risk of both heart disease and breast cancer. Work with a Registered Dietitian to learn the foods that will nourish and strengthen you, and fit your lifestyle and culture.
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