Am Fam Physician. 2008 Mar 15;77(6):842.
Background: Fruits and vegetables may have a role in decreasing breast cancer risk because they contain anticarcinogens. In addition, high-fat diets appear to increase this risk. It is less clear if a diet high in fruit and vegetables and low in fat has a beneficial impact on breast cancer recurrence. One study found that reducing fat intake prolonged relapse-free survival, although the effect was small. The Women's Healthy Eating and Living trial studied the effect of a diet high in fruits, vegetables, and fiber and low in fat on breast cancer recurrence.
The Study: Patients with breast cancer were randomized to an intensive dietary intervention group or a comparison group instructed to consume five portions of fruits and vegetables a day. Eligibility criteria included women with primary operable stage I through stage IIA breast cancer diagnosed between 18 and 70 years of age and within the previous four years. The intensive dietary intervention group received frequent phone interventions, 12 cooking classes, monthly newsletters, and had a targeted daily intake of five vegetable servings, 16 oz of vegetable juice, three fruit servings, 30 g of fiber, and 15 to 20 percent of calories from fat. The comparison group received printed material recommending five servings of fruit and vegetables daily, with follow-up newsletters and an offer of up to four cooking classes. Dietary intake was measured for all participants by 24-hour recall occurring at baseline, one year, four years, and six years. In addition, 50 percent of participants were contacted randomly at various study points for diet assessment. Information was also gathered on breast cancer risk and health status. Outcome measurements were breast cancer recurrence or new primary cancer, or death from any cause.
Results: Of the 7,572 women originally screened, 1,537 were included in the intervention group and 1,551 in the comparison group. No significant differences in diet, mean body weight, or energy intake were observed between groups at baseline. Six years later, a large difference in dietary patterns was observed in the intervention group compared with baseline, whereas the comparison group showed only modest changes. Participants in the intervention group averaged 7.8 daily servings of vegetables at one year, and were able to maintain a similarly high intake over the following years. At year 4, the intervention group was consuming 65 percent more vegetable servings, 25 percent more fruit servings, 30 percent more fiber, and 13 percent less energy from fat than the comparison group. These differences were all statistically significant and corroborated by differences in plasma carotenoid levels. There were no significant differences at any time between groups in overall energy intake and body weight.
Of the 518 participants with breast cancer recurrence or new primary breast cancer, 256 (16.7 percent) were in the intervention group and 262 (16.9 percent) in the comparison group, indicating no significant difference. These results remained unchanged after adjustment for potential confounding factors. Of the 315 women who died (most from breast cancer), 155 (10.1 percent) were in the intervention group and 160 (10.3 percent) were in the comparison group. Group effects by quartile analysis did not yield any new findings.
Conclusion: In this seven-year study, very high levels of fruit and vegetable consumption did not delay or prevent breast cancer recurrence in women with a history of breast cancer, nor did this diet alter mortality. The beneficial impact on disease-free survival observed in previous studies may have been because of weight-loss differences rather than dietary composition. This study does not rule out the possibility that weight loss and physical exercise have survival benefits for patients with breast cancer.
Pierce JP, 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 Healthy Eating and Living (WHEL) randomized trial. JAMA. July 18, 2007;298(3):289–298.
Copyright © 2008 by the American Academy of Family Physicians.
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