专业术语—低脂食物并不能减少健康风险2
Others said that diet could still make a difference, at least with heart disease, if people were to eat the so-called Mediterranean diet, low in saturated fats like butter and high in oils like olive oil. The women in the study reduced all kinds of fat.
The diets studied "had an antique patina," said Dr. Peter Libby, a cardiologist and professor at Harvard Medical School. These days, Dr. Libby said, most people have moved on from the idea of controlling total fat to the idea that people should eat different kinds of fat.
But the Mediterranean diet has not been subjected to a study of this scope, researchers said.
And Barbara V. Howard, an epidemiologist at MedStar Research Institute, a nonprofit hospital group, and a principle investigator in the study, said people should realize that diet alone was not enough to stay healthy.
"We are not going to reverse any of the chronic diseases in this country by changing the composition of the diet," Dr. Howard said. "People are always thinking it's what they ate. They are not looking at how much they ate or that they smoke or that they are sedentary."
Except for not smoking, the advice for a healthy lifestyle is based largely on indirect evidence, Dr. Howard said, but most medical researchers aGREe that it makes sense to eat well, control weight and get regular exercise.
That is also what the cancer society recommends. Dr. Thun, who described the study's results as "completely null over the eight-year follow-up for both cancers and heart disease," said his group had no plans to suggest that low-fat diets were going to protect against cancer.
Others cautioned against being too certain that a particular diet would markedly improve health, and said that whether someone developed a chronic disease might not be entirely under their control — genetics also plays a role.
David A. Freedman, a statistician at the University of California, Berkeley, who is not connected with the study but has written books on the design and analysis of clinical trials, said the results should be taken seriously.
"The studies were well designed," Dr. Freedman said, "and the investigators tried to confirm popular hypotheses about the protective effect of diet against three major diseases in women."
"But," he added, "the diet studied here turned out not to be protective after all."
The study was part of the Women's Health Initiative of the National Institutes of Health, the same program that showed that hormone therapy after menopause might have more risks than benefits.
