A low-fat diet probably does help reduce the risk of breast cancer, says a lead researcher for the Women's Health Initiative (WHI) dietary modification trial.

Although a report on the study in the February 8, 2006 issue of JAMA said, "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," it noted that the nonsignificant trends toward reduced risk indicate follow-up "may yield a more definitive comparison."

At the "WHI Legacy to Future Generations of Women" conference in Bethesda, Md., Ross Prentice, PhD, said the results were reported far too dismissively, particularly in the popular press. Among other supporting data, he noted, "We see a greater evidence of reduction in breast cancer risk among the group that started higher [in dietary fat] and made a bigger change. So these are data that you would not expect to see if the intervention was doing nothing relevant to breast cancer risk."

In the huge study of almost 49,000 women, breast cancer rates were 9% lower in those who were taught to eat a lower-fat diet than in the comparison group. The original hypothesis was based in part on findings of breast cancer rates that are up to fivefold higher in nations with high-fat diets, such as the United States, compared to those with low-fat diets.

The researchers indicated that the benefit may not have reached a level of significance because dietary fat intake was not low enough in the dietary change group or that the follow-up period was not long enough.