Low-Fat Diet Fails to Curb Diseases: Cancer, Heart Ills Not Reduced for Older Women

By Kawanza Newson, Milwaukee Journal Sentinel

Feb. 8–Eating a low-fat diet won’t reduce women’s risk of cancer or heart disease, deflating the belief that postmenopausal women who change their diets can potentially affect their development of certain diseases.

However, experts caution that the findings are not an excuse to continue or start bad eating habits.

“We don’t know how much diet will help your risk of cancer, but if you eat a better diet and maybe lose a few pounds, you might not reduce your risk, but you’ll feel better and your overall quality of life will be better,” said James A. Stewart, an oncologist and professor of medicine at the University of Wisconsin’s Comprehensive Cancer Center in Madison who was not involved in the study.

Almost the entire issue of today’s Journal of the American Medical Association is devoted to studies on whether a diet that is low in fat but high in fruit, vegetables and grains can reduce a woman’s risk of specific cancers or cardiovascular disease.

The three studies — assessing risk of breast cancer, colorectal cancer and heart disease — were based on research from the Women’s Health Initiative, best known for its landmark finding in 2002 that taking hormones after menopause raised the risk of certain cancers and heart problems. The studies involved more than 48,000 postmenopausal women, nearly 1,200 from Milwaukee, who were followed for about eight years.

One group reduces fat intake

The women were assigned to either a control group that maintained typical eating habits or to a dietary intervention group that learned diet and behavior changes to reduce total fat intake to 20% while increasing consumption of fruits and vegetables to at least five servings and grains to at least six servings.

However, many women in the intervention group were unable to meet the dramatic reduction in fat during the study. In addition, the women in the study tended to have a high body mass index, and most didn’t see significant changes in their weight.

The same group involved in the current studies previously reported that after about seven years, the control group weighed about the same as when the study started and the intervention group — which had lost weight initially — regained most of it.

Fighting breast cancer

The main priority of the reports was to determine whether the diet could reduce the risk of breast cancer, the most common cancer in American women. Though the incidence of breast cancer was 9% lower in the diet group compared with the control group, the difference was not statistically significant.

However, significant results also were seen among women in the low-fat diet group who began the study with the highest baseline fat consumption and among women who most strictly adhered to the study’s dietary-fat goals. Women in these categories experienced a 15% to 20% overall reduction in breast cancer incidence.

“The bottom line is that changing to a low-fat diet may reduce breast cancer risk, especially among women who have a relatively high-fat diet to begin with, but we don’t view our data as strong enough at this time to make a broad recommendation that all women initiate a low-fat diet for that purpose,” said Ross Prentice, a biostatistician at the Fred Hutchison Cancer Research Center in Seattle who was involved in the study.

“Additional research is needed to determine the specific dietary elements that may help prevent breast cancer, the optimal time to initiate dietary interventions, and the duration these diets should be followed to achieve the maximum benefit,” wrote Aman U. Buzdar, professor and deputy chairman of medicine in the department of breast medical oncology at the University of Texas M.D. Anderson Cancer Center in Houston, in an editorial accompanying the study in the journal.

Though the results were more conclusive for colorectal cancer, whose risk has previously been shown to increase with a high consumption of red meat and processed meat, the study’s design was not adequate to answer the question about heart disease, Prentice said.

For example, it’s known that specific types of fats, not overall fat intake, are most important, he said.

Also, it’s unclear whether studying a younger set of women would have yielded more conclusive different results. The ages of the women in the study range from 50 to 79.

“These are chronic conditions that take many years to develop,” said Jane Kotchen, a professor of epidemiology at the Medical College of Wisconsin who was involved in the study.

Regardless, “it seems advisable for women to eat a prudent diet based on recent Dietary Guidelines for Americans, which provides an overall plan for healthy eating,” she said.

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