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Influence of a Diet Very High in Vegetables, Fruit and Fiber and Low in Fat on Prognosis Following Treatment for Breast Cancer

Introduction:
Previous evidence from preclinical studies indicates that plant-derived foods contain anticarcinogens. In addition a comprehensive review of the literature found that a diet high in vegetables and fruit probably decreases breast cancer risk while a diet high in total fat would increase risk. However, evidence is lacking that a consistent diet high in vegetables, fruit, and fiber while low in total fat can influence breast cancer recurrence or survival. A medical study was conducted to assess whether a major increase in vegetable, fruit, and fiber intake and a decrease in dietary fat intake reduces the risk of recurrent and new primary breast cancer and all-cause mortality among women with previously treated early stage breast cancer.

Methods:
The 3088 female participants, aging from 18 to 70 years of age at diagnosis, were enrolled in the study. All women had been previously treated for early stage breast cancer at diagnosis. Participants were enrolled between 1995 and 2000, and followed through June 2006. The participants were split into two groups, one for intervention and the other for comparison (the control group). The intervention participants agreed to consume a 5-A-Day diet requiring an intake of 5 vegetable servings plus 16 oz of vegetable juice, 3 fruit servings, 30 g of fiber, and 15% to 20% of energy intake from fat, each day. The primary evaluation would examine two end points: (1) the combined outcome of invasive breast cancer reoccurrence or new primary breast cancer and, (2) death from any cause.

Results:
Over the course of the study, 518 participants experienced a breast cancer event and 315 deaths were reported, with more than 80% of them due to breast cancer.
At baseline there was no significant difference in dietary intake between the groups
with both groups consuming a daily average of more than 7 servings of fruits and vegetables, there no observed differences in fiber, fat or energy intake.
The study results showed that the intervention group achieved and maintained the following statistics vs. the comparison group through 4 yrs: +65% servings of vegetables, +25% fruit, +30% fiber, -13% energy intake from fat. Plasma carotenoid concentrations were used to validate changes in fruit and vegetable intake.

Over the 7.3 yr follow up, 256 women in the intervention group (16.7%) and 262  (16.9%) in the comparison group experienced an invasive breast cancer event; 155 from the intervention group vs 160 from the comparison group died.  No significant interactions were observed between the diet group and baseline demographics, characteristics of the original tumor, or breast cancer treatment.

Conclusion:
Among the remaining participants of early stage breast cancer, the diet high in vegetables, fruit, fiber and low in fat did not significantly reduce further breast cancer events or mortality in the 7.3 year follow up period.

Study Limitations:
At baseline, both groups consumed a daily average of more than 7 servings of fruits and vegetables; significantly highly than the average American’s consumption of ~3.5 servings of both fruits and vegetables combined. Additionally it was not found that the possibility that increased exercise and weight loss might benefit breast cancer survivors. Lastly, the study did not address whether consuming the high-vegetables/fruit/fiber and low-fat diet of the study intervention early in life would alter risk of primary breast cancer. The study also did not investigate whether weight loss and exercise would be beneficial in reducing the risk for breast cancer in addition to the high fruit/vegetable/fiber and low fat diet. In a separate study, Pierce and colleagues found a greater survival after early-stage breast cancer in women physically active with high fruit and vegetable intake regardless of obesity.

Literature Citation :
Pierce J, Natarajan L, Caan B, 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.2007;298:289-298.

Pierce JP, Stefanick ML, Flatt SW, et al. Greater survival after breast cancer in physically active women with high vegetable/fruit intake regardless of obesity. J Clin Oncol. 2007;25(17);2345-2351.