On the heels of the "null findings" of Women's Health Initiative Dietary Modification Trial for reduction of risk in breast cancer and cardiovascular disease, we're seeing a call for continued follow-up and more rigorous restrcition of dietary fat to prove a low-fat diet offers some protection to health.
Have we lost our minds?
The biggest study so far investigating the relation between breast cancer and fat intake is the Nurses' Health Study, conducted by Harvard University Medical School. A total of 88,795 women free of cancer in 1980 were followed up for 14 years. Comparing breast cancer rates in women who derived more than thirty percent of their calorie intake from fat with women who derived less than twenty percent of calories from fat, they show that those on low-fat diets had a higher rate of breast cancer than those who ate more total fat.
Dr Michelle Holmes and colleagues concluded: "We found no evidence that lower intake of total fat or specific major types of fat was associated with a decreased risk of breast cancer."
Yet the researchers for the WHI trial want more time? To show what - a trend toward a higher incidence of breast cancer in the women eating low-fat diets?
In 1997 the Nurses' Heath Study (noted above) researchers found that "Total fat intake was not signficantly related to the risk of coronary disease."
In 1997 it was found that low-fat, high-carbohydrate diets [15% protein, 60% carbohydrate, 25% fat] increase the risk of heart disease in post-menopausal women. The researchers were clear in their conclusion that a low-fat diet "would increase risk of ischemic heart disease in postmenopausal women," and that "it seems reasonable to question the wisdom of recommending that postmenopausal women consume low-fat, high-carbohydrate diets."
Dr. Gerald M. Reaven, of Stanford University School of Medicine in California, and colleagues compared the effects of a low-fat, high-carbohydrate diet [25% fat, 60% carb, 15% protein] with a high-fat, lower-carbohydrate diet [45% fat, 40% carb, 15% protein], on blood fats and cholesterol. They found their subjects had significantly higher fasting plasma triglyceride concentrations, remnant lipoprotein cholesterol concentrations, and remnant triglyceride concentrations when they were on the high-carbohydrate, low-fat diet, both after fasting and after breakfast and lunch. The study participants also had significantly lower HDL (the 'good' cholesterol) concentrations on this diet.
The authors conclude: "Given the atherogenic potential of these changes in lipoprotein metabolism, it seems appropriate to question the wisdom of recommending that all Americans should replace dietary saturated fat with CHO [carbohydrate]."
In 2004, researchers concluded that "In postmenopausal women with relatively low total fat intake, a greater saturated fat intake is associated with less progression of coronary atherosclerosis, whereas carbohydrate intake is associated with a greater progression." The women followed were consuming an average of 25% total fat - lower than the women in the WHI trial.
Yet the researchers for the WHI trial want more time? To show what - a trend toward a higher incidence of cardiovascular disease in the women eating low-fat diets?