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Increasing Vegetable and Fruits Beyond Current Dietary Guidelines Does Not Reduce Breast Cancer Recurrence or Death, According to a New Study

Diet and Breast Cancer

Eating a diet very high in vegetables, fruit and fiber and low in fat, did not reduce breast cancer recurrence or death in early stage breast cancer survivors, according to a study published in the July 18, 2007 issue of the Journal of the American Medical Association (JAMA). The study is the largest randomized clinical trial to assess the influence of diet on additional breast cancer events.

The results are part of the multi-center Women’s Healthy Eating and Living (WHEL) study, designed to investigate the effects of a nutrient-dense, fiber-rich, plant-based diet on additional breast cancer events. Participating institutions included the UCSD Moores Cancer Center, the Kaiser Permanente Division of Research in Oakland CA; the Kaiser Permanente Center for Health Research in Portland, Oregon; University of California, Davis; Stanford University; University of Arizona at Tucson, and the University of Texas M.D. Anderson Cancer Center in Houston.

“For the typical woman diagnosed with early stage breast cancer, there is no additional benefit from dramatically increasing consumption of plant-based foods rich in ‘cancer preventive’ compounds, compared to following the recommended healthy diet,” said John Pierce, PhD, director of the Cancer Prevention and Control Program at the Moores UCSD Cancer Center

“These results do not mean that women should stop paying attention to what they eat,” said Bette Caan, Dr.P.H., senior epidemiologist at the Kaiser Permanente Division of Research in Oakland, California. “In addition, being physically active, eating a diet with plenty of fruits and vegetables and moderate in fat is still one of the best ways we know to maintain a healthy weight.”

The WHEL study followed 3,088 women, ages 18 to 70, for between 6 and 11 years. Participants were randomly assigned to one of two diet groups. The comparison group followed the guidelines promoted by the U.S. Department of Agriculture (USDA), which include five vegetable and fruit servings per day, at least 20 grams of fiber per day and 30 percent fat.

The intensive intervention group was asked to follow a daily dietary pattern that included five vegetable servings, 16 fluid ounces of vegetable juice, 3 fruit servings, 30 grams of fiber and 15-20 percent of energy from fat.

At the start of the study, both groups consumed similar amounts of vegetables and fruits (7 servings a day on average), fiber and calories form fat. Telephone counseling helped women assigned to the intensive dietary group to change their diets substantially. At the end of the first year of observation, women in the intervention group had increased their vegetable and fruit intake to an average of 12 servings a day. They also increased their fiber intake substantially and decreased fat intake. These large changes in self-reported dietary pattern were validated by large changes in plasma carotenoid concentrations. By the fourth year of the trial, relative to the comparison group, the intensive dietary group was still consuming more vegetable servings (+65 percent), more fruit servings (+25 percent), more fiber (+30 percent), and less energy from fat (-13 percent). The difference in diets between the two groups was maintained throughout the trial.

After a median of 7 years of follow-up, the study observed no difference in recurrence or survival between groups. About 17 percent of women in both diet groups developed a breast cancer recurrence or new breast cancer and 10 percent of women in both groups died.

The results do not rule out the possibility that following a diet extremely high in fruits, fiber and low in fat from a young age would be helpful. Further more, researchers will be investigating specific subgroups within this study to determine if any of the women might have received some additional benefit from the dietary change.

In addition to John Pierce, a faculty member in the Department of Family and Preventive Medicine at the UCSD School of Medicine, other UCSD authors include Shirley W. Flatt, Loki Natarajan, Lisa Madlensky, Wael K. Al-Delaimy, Sheila Kealey, Barbara A. Parker, Vicky A. Newman, Cheryl L. Rock, Wayne Bardwell, Jennifer A. Emond, Susan Faerber, Kathryn Hollenbach, and Linda Wasserman.

In addition to Bette Caan, Kaiser Permanente Division of Research, Oakland, Calif., other authors include: Njeri Karanja, the Kaiser Permanente Center for Health Research in Portland, Oregon; Marcia L. Stefanick, Stanford Prevention Research Center; Robert Carlson, Stanford Comprehensive Cancer Center; Cynthia A. Thompson and Cheryl Ritenbaugh, University of Arizona; Richard Hajek and Lovell A Jones, MD Anderson Cancer Center; Ellen B. Gold, UC Davis; James Marshall, Roswell Park Cancer Institute Buffalo; and E. Robert Greenberg, the Fred Hutchinson Cancer Center.

This work was initiated with support by the Walton Family Foundation, with the major part of the study supported by grants from the National Cancer Institute.

Founded in 1979, the Moores UCSD Cancer Center is one of just 40 centers in the United States to hold a National Cancer Institute (NCI) designation as a Comprehensive Cancer Center. As such, it ranks among the top centers in the nation conducting basic, translational and clinical cancer research, providing advanced patient care and serving the community through innovative outreach and education programs.

The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and the society at large. It seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 400-plus staff is working on more than 250 epidemiological and health services research projects.

Kaiser Permanente is America’s leading integrated health plan. Founded in 1945, it is a not-for-profit, group practice program headquartered in Oakland, Calif. Kaiser Permanente serves more than 8.7 million members in nine states and the District of Columbia. Today it encompasses the not-for-profit Kaiser Foundation Health Plan, Inc., Kaiser Foundation Hospitals and their subsidiaries, and the for-profit Permanente Medical Groups. Nationwide, Kaiser Permanente includes approximately 156,000 technical, administrative and clerical employees and caregivers, and 13,000 physicians representing all specialties. For more Kaiser Permanente news, visit the KP News Center at:

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