Reason for Optimism? continued...
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."
Good Fats and Bad
U.S. Dietary guidelines recommend that between 20% and 35% of daily calories come from fat, with saturated fat accounting for less than 10% of daily calories. The guidelines call for limiting saturated fats and trans fats in favor of unsaturated fats, such as those found in fish, nuts, and certain vegetable oils.
The WHI study did not make the distinction between so-called "good fats" and "bad fats," however, and the researchers say this may have influenced the findings.
There has been a shift in thinking about the role of dietary fat in disease since the trial was designed in the early 1990s. The emphasis now is on reducing saturated fats and trans fats in the diet, rather than reducing overall fat consumption.
The link between cardiovascular disease and diets high in saturated fat has been well established.
"This study shows that just reducing total fat intake does not go far enough to have an impact on heart disease risk," says Jacque Rossouw, MD, adding that women who are following diets low in saturated and trans fats should be encouraged to continue doing so.
"We have a pretty clear signal that women who are still eating [high-fat diets] would be well advised to reduce their fat intake," he says.