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.
