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Low-Fat Diet Not Associated With Reduced Risk of Breast, Colorectal CancerA low-fat diet is not associated with a reduced risk of colorectal cancer or breast cancer, according to a randomized controlled trial of nearly 50,000 women.
International comparison studies have suggested that countries with a lower dietary fat intake have reduced risks of colorectal cancer and breast cancer. The Women's Health Initiative (WHI) Dietary Modification Trial was designed to test whether a low-fat diet reduces the rate of colorectal cancer, breast cancer, and heart disease in 48,835 postmenopausal women aged 50–79 years. About 20,000 of the women were randomly assigned to intensive dietary instruction to increase their fruit, vegetable, and grain consumption. They used self-monitoring techniques and other strategies to reduce fat intake to about 20% of total daily calorie intake. These women were not specifically instructed to lose weight. The control group of women were told to maintain their usual diet.
Researchers diagnosed colorectal cancer at a rate of 0.13% a year in the group of women on a low-fat diet and a rate of 0.12% per year in the control group. They diagnosed breast cancer at a rate of 0.42% a year in the group of women on a low-fat diet and a rate of 0.45% a year in the control group. These differences were not statistically significant. The low-fat diet also had no effect on the incidence of cardiovascular disease, coronary heart disease, or stroke.
The researchers note that few women were actually able to reduce fat intake to 20% of total calories: Only 31% met that goal after 1 year and 14% did after 6 years. Nevertheless, the women in the dietary intervention group did consume a lower-fat diet and ate on average one more serving of fruits and vegetables per day than the control group.
The studies were published in the February 8 issue of the Journal of the American Medical Association.
Noninvasive Diagnostic Tests Not Accurate Enough To Replace Biopsies, Study Reports
Four noninvasive breast cancer examinations—magnetic resonance imaging, ultrasonography, positron emission tomography scanning, and scintimammography—do not have the accuracy to replace biopsies to detect cancer in women who have abnormal findings on a mammogram or physical examination, according to a new meta-analysis by the Agency for Healthcare Research and Quality, part of the U.S. Department of Health and Human Services.
Four-fifths of women who have a breast biopsy because they had an abnormal mammogram or physical examination do not test positive for breast cancer. A noninvasive screening test would reduce the number of invasive biopsies for women who do not have cancer.
AHRQ's review included 81 studies of four noninvasive screening methods: MRI, ultrasonography, PET scan, and scintimammography. The agency's analysis showed that these tests would miss 4%–9% of all cancer cases in women with an average risk of breast cancer.
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