Ross L. Prentice, Ph.D., of the Fred Hutchinson Cancer Research Center, Seattle, and colleagues with the Women's Health Initiative (WHI) Dietary Modification Trial, examined the effect of a low-fat diet on the incidence of breast cancer. The WHI, which began in 1992 with 48,835 postmenopausal women without prior breast cancer, included a dietary modification intervention consisting of consumption of a reduced amount of fat (20 percent of energy) and of an increased amount of vegetables and fruits (5 or more servings a day) and grains (6 or more servings a day). The women, aged 50 to 79 years, were randomly assigned to the dietary modification intervention group (40 percent, n = 19,541) or the comparison group, who were not asked to make dietary modifications (60 percent, n = 29,294). It has been hypothesized that a low-fat diet can reduce breast cancer risk, but previous studies have had mixed results.

The average follow-up time was 8.1 years. Overall, 655 (3.35 percent) women in the intervention group and 1,072 (3.66 percent) women in the comparison group developed invasive breast cancer during follow-up.

"Among postmenopausal women, a low-fat dietary pattern did not result in a statistically significant reduction in invasive breast cancer risk over an 8.1 year average follow-up period. However, the nonsignificant trends observed suggesting reduced risk associated with a low-fat dietary pattern indicate that longer, planned, nonintervention follow-up may yield a more definitive comparison," the authors conclude.

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Contact: Kristen Woodward
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JAMA and Archives Journals
7-Feb-2006