Low-Fat Diet May Not Cut Cancer Risk
Study Fails to Show Lower Risk in Women of Breast Cancer and Heart Disease
Feb. 7, 2006 - A study of almost 50,000 postmenopausal women shows little
evidence that following a low-fat diet reduces the risk of breast cancer,
colorectal cancer, or even heart disease.
Researchers stopped short of calling findings from the $415 million Women's
Health Initiative (WHI) Dietary Modification Trial disappointing, saying,
instead, that longer follow-up of the women in the study may prove the
disease-fighting benefits of a low-fat diet.
But significant reductions in breast cancer, colorectal cancer, and heart
disease were not seen in the majority of women in the study who ate low-fat
diets high in fruits, vegetables, and grains for an average of eight years.
Nonetheless, investigators at a news conference today called the findings
consistent with current disease-prevention guidelines.
"The results of this study do not change established recommendations for
disease prevention," says National Heart, Lung, and Blood Institute
Director Elizabeth G. Nabel, MD.
"Women should continue to get regular mammograms and screenings for
colorectal cancer, and work with their doctors to reduce their risks for heart
disease, including following a diet low in saturated fat, trans fat, and
Largest Low-Fat Trial
Results from this study, the largest intervention study to evaluate low-fat
diets, are reported in The Journal of the American Medical
From 1993 to 2005, the study included 48,835 postmenopausal women aged 50 to
79 who either agreed to follow a low-fat diet or were told to continue eating
as they had been.
By the end of the first year, the low-fat-diet group had reduced their
average total fat intake to 24% of their daily calories. By the sixth year of
the study, 29% of their daily calories came from fat.
In contrast, fat accounted for roughly 35% of daily calories consumed by
women in the nonintervention group during the first year of the study and 37%
of daily calories in the study's sixth year.
Reason for Optimism?
During an average of eight years of follow-up, women who reduced their total
fat intake did not have reduced risk for colorectal cancer. The researchers
write that whether greater adherence to the low-fat diet, longer follow-up, and
starting a low-fat diet earlier on would have made a difference to the risk for
colorectal cancer "remain unanswered questions."
Women in the low-fat group had a 9% lower risk of breast cancer than women
who made no dietary changes, which is not a significant reduction. But Nabel
and other experts say there is reason for optimism in the findings.
And reductions in risk were greatest among women who had cut their overall
fat intake and saturated fat intake the most. The researchers say longer
follow-up may show a clearer difference.
"It is best to say at this point that we have evidence of some
relationship between breast cancer risk and (dietary) fat content," says
the study's principal researcher, Ross Prentice, PhD. "But we should
probably leave it at that."