According to the results of a study published Journal of the American Medical Association, breast cancer survivors assigned to a diet very high in fruits and vegetables and low in fat had a similar risk of breast cancer recurrence as women who were advised to follow the “5-A-Day” dietary guidelines.
For women who have been treated for early-stage breast cancer, an important focus of life after treatment is how to stay healthy and avoid a cancer recurrence. In response, researchers have been exploring the effects of factors such as diet, exercise, and body weight on risk of breast cancer recurrence.
Studies have suggested that a diet rich in fruits and vegetables may reduce the risk of breast cancer. Some studies have also suggested that a diet low in fat may provide benefits, but these studies have been less consistent.
To explore the effects on breast cancer recurrence of a diet very high in fruits, vegetables, and fiber and low in fat, researchers conducted a study known as the Women’s Healthy Eating and Living (WHEL) study. The study enrolled more than 3,000 women between the ages of 18 and 70 years who had been treated for early-stage (Stage I to Stage IIIA) breast cancer.
Half the women in the study were assigned to the diet high in fruits and vegetables and low in fat. The daily target for these women was five servings of vegetables plus one 16-ounce serving of vegetable juice; three servings of fruit; 30 grams of fiber; and 15–20% percent of calories from fat. The study provided women with telephone counseling, cooking classes, and newsletters to help them reach these goals.
The other half of the study participants served as a comparison group. These women were advised to follow the “5-A-Day” dietary guidelines, which encourage five servings of fruits and vegetables a day, more than 20 grams of fiber, and less than 30 percent of calories from fat.
Over the course of the study, women assigned to the diet high in fruits and vegetables and low in fat did consume more fruits and vegetables than women in the comparison group. They also consumed somewhat less fat, although average fat intake remained above what was recommended.
The frequency of cancer recurrence and death was assessed after an average of seven years of follow-up.
- 16.7% of the women in the dietary intervention group and 16.9% of women in the comparison group experienced a breast cancer recurrence or a new breast cancer.
- 10.1% of the women in the dietary intervention group and 10.3% of women in the comparison group died.
These results-which indicate no effect of the dietary intervention on risk of breast cancer recurrence or death-differ from the results of a previous study known as the Women’s Intervention Nutrition Study (WINS). In WINS, women assigned to a low-fat diet had a reduced risk of breast cancer recurrence. A possible explanation for these differing results is that women in the low-fat group of the WINS study experienced significant weight loss. In contrast, the two study groups in the WHEL study had generally similar body weight throughout the study. It’s possible that weight control-rather than the low-fat diet per se-may explain the benefit observed in the WINS study.
The results of the WHEL study should not discourage women from eating a diet rich in fruits and vegetables. Fruits and vegetables remain an important part of a healthy diet.
Reference: Pierce JP, Natarajan L, Caan BJ et al. Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer: The Women’s Health Eating and Living (WHEL) Randomized Trial. JAMA. 2007;298:289-298.