Lower-fat diet reduces breast cancer risk

Women who followed a lower-fat diet rich in fruits, vegetables and grains had a lower risk of dying from breast cancer than those on a higher-fat diet, according to results from a major new study released Wednesday.

The conclusions, from the latest analysis of the federally funded Women’s Health Initiative, provide the first randomized clinical trial evidence that diet can reduce postmenopausal women’s risk of dying from breast cancer, the researchers said. Past observational studies — which don’t measure cause and effect — have had inconsistent findings.

The results “are exciting and empowering for the patient,” said Elisa Port, chief of breast surgery at Mount Sinai Health System, who was not involved in the study. “This is a wake-up call for women — there’s something they can do rather than just waiting for the shoe to drop.”

The trial involved more than 48,000 women who did not have breast cancer when they enrolled in the study conducted at 40 centers across the United States. From 1993 to 1998, the women were randomly assigned either to follow their usual diet, in which fat accounted for 32 percent of daily calories on average, or to try to reduce fat intake to 20 percent of calories while consuming daily servings of vegetables, fruit and grains.

The dietary-intervention group fell short of the goal; they managed to reduce their fat consumption to about 24.5 percent, and then “drifted up to about 29 percent,” according to lead study author Rowan Chlebowski of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center. Members of the group lost 3 percent of their body weight on average. Still, the women in that group who developed breast cancer had a lower risk of death than the women who followed their regular diets and developed the disease.

Chlebowski said the study showed that women could improve their health by making modest changes in what and how much they eat. “This is dietary moderation, it’s not like eating twigs and branches,” he said. “It’s what people were eating, say, 20 years ago, before you could pick up 900 calories in one candy bar.”

Breast-cancer experts generally praised the study but expressed some reservations. In particular, the study was designed not to determine whether a low-fat diet provided a mortality benefit but whether such a diet could reduce the risk of developing breast cancer in the first place.