Risks for women from heart attacks, strokes, colon and breast cancer are unaffected by low-fat diets, a $415 million study has found. The eight-year study of close to 50,000 middle-aged to elderly women found no clear cut evidence that cutting fat from diets reduces the risks of these illnesses.

This new study reverses a key, long standing recommendation that was based on the belief that a low-fat diet would have many positive health benefits.

“Based on our findings, we cannot recommend that most women should follow a low-fat diet” said Jacques Rossouw from the National Heart, Lung and Blood Institute, which funded the study. He added that although the study involved only women, the findings probably apply to men as well.

Despite these findings, several experts warned that the study showed some possible evidence to support reducing fat in a diet, especially for breast cancer.

“I think women who are currently following a low-fat diet should still be encouraged to do so. We didn’t see any unfavorable effects,” said Ross Prentice of the Fred Hutchinson Cancer Research Center in Seattle. “For women who are at a high risk for breast cancer, they should talk it over with their physicians as to whether adopting a low-fat diet might be warranted.” He also emphasized that women on the diet did avoid gaining weight.

Data from 48,835 women age 50 to 79 was analyzed by researchers for the study. Close to 40 percent were told to cut their fat intake as well as to eat more fruits and vegetables. They were aiming to reduce their overall fat intake to less than 20 percent of their daily calories.

About eight years later, these women had cut their total fat from 35-38 percent to 24-29 percent, while the remainding 60 percent continued their fat intake at the same level.

The results, published in the Journal of the American Medical Association, failed to find any significant evidence that the low-fat diets reduced the risk of heart attack and disease, stroke, and colon and breast cancer.

“We had hoped that this approach would prove to be beneficial,” Barbara Howard of the MedStar Research Institute said. “I think we’ve learned that nutrition is never simple and there are no simple solutions.”