Diet Double In Fruits, Vegetables Does Not Prevent Breast Cancer Recurrence, National Study Finds
An extremely low-fat diet rich in fruits, vegetables and fiber neither reduces the risk of breast cancer recurrence in women, nor increases the chance for survival any more than the nationally recommended "5-a-day," according to a pivotal study published in the July 18 issue of the Journal of the American Medical Association.
The largest and most comprehensive diet prevention study ever conducted, The Women's Healthy Eating Living (WHEL) was supported by the National Cancer Institute and enrolled 3,088 women previously treated for early stage breast cancer. Seven institutions across the country participated in the study, with the Moores Cancer Center at the University of California, San Diego serving as the coordinating site.
The University of Texas MD Anderson Cancer Center enrolled 380 breast cancer survivors, including 50% (50 women) of the African American women who participated in the study. Lovell Jones, Ph.D., professor in the Department of Health Disparities Research Center, says the study's results were extremely surprising.
"The WHEL's findings are pivotal because we always assumed that we were not eating enough fruits and vegetables and the more we ate, the more protected we would be against cancer," says Jones, the study's principal investigator at MD Anderson.
"Earlier observational studies of the WHEL's own control group saw a 40% increase in survival. Additionally, a report of interim analysis from the Women's Intervention Nutrition Study found that a low fat diet might reduce the risk of recurrence. Given these findings, we really did think that we would see a significant statistical difference in the recurrence and survival rates between the women who adopted a super healthy lifestyle compared to those that ate the recommended allowance."
The 10-year randomized trial enrolled participants between 1995 and 2000; all of the patients were 18-70 years old and survivors of early stage breast cancer, up to Stage IIIA. The comparison group (1551 women) followed the "five-a-day" healthy diet, were given written material regarding a healthy lifestyle, offered four cooking classes during the first year and received bimonthly newsletters. In contrast, the intervention group (1537 women) adopted a diet double in vegetable and fruit daily servings, high in fiber and low in fat. They were intensively monitored with frequent phone counseling sessions, were offered 12 cooking classes during the first year and received monthly newsletters.
There was a 90% compliance rate in the study and the women in the intervention group averaged an intake of nine servings of fruits and vegetable a day, both very impressive statistics, says Jones. The study's primary endpoints were combined outcome of breast cancer recurrence or a new primary cancer diagnosis and death from any cause. The women were followed for 7.3 years.
There was no statistical difference in either the recurrence or death rates in the two groups. During the study, 518 of the women - 256 (16.7%) from the intervention group and 269 (16.9%) from the comparison group - had a recurrence of their breast cancer, or developed a second primary. A total of 315 women, 155 (10.1%) from the intervention group and 160 (10.3%) from the comparison group died during the study.
"With these findings, it is imperative that we not discount the importance of a healthy diet and its role in cancer prevention," says Jones. "It is important to remember that our control group was eating the recommended guidelines for fruits and vegetables."
What the study did not account for, explains Jones, is what the participants were eating prior to their enrollment into the study, be it healthy or not. He believes that for the greatest preventative effect, women must make healthy changes to their diet long before a possible diagnosis of breast or any other type of cancer.
"Another factor that undoubtedly impacted our findings was the improvement in therapy over the last decade. We have made more strides in the treatment of breast cancer in the last 10 years than we had in the 25 years before that. It is very possible that we are seeing the impact of better therapy on both sides of our study," says Jones.
Future studies examining the outcome of the minorities enrolled in the trial are planned, says Jones.
The study was funded by the National Cancer Institute and a foundation gift from the Walton Family Foundation.
MD Anderson's Center for Research on Minority Health is one of National Institute's of Health/National Center on Minority Health and Health Disparities' Center of Excellence.