23 Does Eating More Fruit and Vegetables Reduce the Risk of Breast Cancer?

Does Eating More Fruit and Vegetables Reduce the Risk of Breast Cancer?

Results from the WHEL Study

Women who have been diagnosed with breast cancer often pay extra attention to their diet as a way to prevent recurrence of their cancer. Healthcare professionals and researchers alike have long suspected a correlation between healthful eating patterns and reduced risk of chronic diseases such as certain forms of cancer and heart disease.

Recently, several studies related to these issues have been making the headlines, and you may feel as though you have heard conflicting information about what role a plant-based diet, specifically, plays in your risk of developing cancer. It may help to take a look at one of these studies—the Women’s Healthy Eating and Living (WHEL) study—and see how the research can help you make decisions about your own nutrition plan.

The WHEL study was a Phase III clinical trial conducted from 1995 to 2000 designed to investigate and confirm early reports that by increasing consumption of fruit, vegetables, and fiber and by subsequently lowering fat, women could reduce breast cancer recurrence or the development of a second primary diagnosis of breast cancer. Research from the Women’s Intervention Nutrition Study (WINS) released in 2005 suggested that following a low-fat diet helped reduce the risk of breast cancer recurrence in postmenopausal women who were initially diagnosed with estrogen receptor–negative breast cancer.

Participants in the WHEL study, which was conducted at seven different medical centers and enrolled a total of 3,088 women ranging in age from 18 to 70 who had been diagnosed and treated for breast cancer (Stages I to IIIA), were divided into two groups at the start of the study. The control group participants (1,551 women) were educated to incorporate the U.S. Department of Agriculture’s (USDA) 5 A Day (www.5aday.org) program to increase consumption of fruit and vegetables to five servings per day, with the intent of achieving a daily intake of 20 grams of fiber each day and less than 30 grams of fat, which follows the USDA’s guidelines for healthy Americans. The remaining participants (1,537 women) were part of the intervention group and were instructed to consume at least three servings of fruit, five servings of vegetables, 16 ounces of vegetable juice, and 30 grams of fiber per day and to limit fat to 15 to 20 percent of daily calories. Intervention group participants received dietary newsletters, cooking classes, and phone-based counseling to help them meet their goals. All participants at the start of the study were consuming diets of similar caloric content and were of comparable body weight.

At the end of the five-year study, significant differences between the two groups were noted. Participants in the intervention group were consuming 65 percent more vegetables, 25 percent more fruit, 30 percent more fiber, and 13 percent less fat than the control group. Even with these significant changes in dietary patterns, however, there were no significant changes in the rate of breast cancer recurrence or diagnosis of a new primary cancers between the two study groups.

According to lead researcher John Pierce, PhD, the limitations of the study could have contributed to the lack of statistically significant change noted among participants. Although the intervention group on average consumed more fruit, vegetables, and fiber, they did not meet the lower fat percentage that was initially recommended in the study. Another problem noted was the slight increase in weight over the course of the study, which indicated that the caloric content of the diets in both groups was greater than initially reported. As with many studies involving nutrition, dietary recalls of the participants are often skewed, leading to problems with their validity.

Does this mean that women diagnosed with breast cancer should not follow a high-fiber, low-fat diet? No. The bottom line is that more research needs to be done to evaluate how diet truly affects the development and the recurrence of breast cancer. In addition, before you throw all the veggies out of the fridge, remember that eating a diet that is rich in plant-based foods can help reduce your risk of heart disease and stroke and can have an overall positive benefit on your health.

Fruits and vegetables are packed full of powerful antioxidants and food components called phytochemicals. Both phytochemicals and antioxidants work to protect cells from damage from free radicals. A practical tip to remember is to eat from the rainbow: aim to add a variety of color to your diet every day to ensure that you are getting a mix of these powerful anticancer substances. As a rule of thumb, aim for at least five servings of fruit or veggies every day, with the goal of having at least three different colors represented.

Until further research has been completed, women can still benefit from the information we have gained from the WHEL and WINS studies, both of which describe a strong correlation between body weight, fat content, and breast cancer risk. Lowering the fat content of your diet, adding fiber, and starting an exercise program or increasing the intensity of your current practice—all can reduce body fat and help you reach a healthy body weight. If you have questions about any of these issues, seeking the professional help of a registered dietitian at your cancer center can be a good first step in making healthy lifestyle changes.