Statement of CSPI Nutrition Director Bonnie Liebman on the Womenís Health Initiative Study
February 8, 2006
Media reports on a recent major study on low-fat diets may mislead the public because they suggest that current advice to reduce the risk of heart disease and cancer are wrong. In fact, the study tested diet advice that is 10 to 20 years out of date.
The Womenís Health Initiative, which randomly assigned almost 50,000 women to eat either a low-fat diet or their typical diet, found no significant difference between the groupsí risks of breast cancer, colorectal cancer, or cardiovascular disease. However, health authorities including the Institute of Medicine of the National Academy of Sciences, the American Heart Association, the American Cancer Society, and the Departments of Health and Human Services and Agriculture have not recommended a low-fat diet for at least a decade, if at all.
Since that time, heart disease experts have recommended replacing bad fats (saturated and trans) with good fats (polyunsaturated and monounsaturated). In the WHI, women who were told to eat a low-fat diet cut back only modestly on all fats, so they did not benefit from an increase in good fats. Furthermore, women on the low-fat diet were eating only slightly less bad fat than the women who were told to eat their usual diets, reducing the odds that researchers would see a difference in the groupsí heart disease rates.
The American Cancer Societyís current diet guidelines recommend eating more fruits and vegetables, choosing whole grains over refined grains and sugars, limiting the consumption of red meats, limiting alcohol, maintaining a healthful weight, and staying physically active.
Unfortunately, many fatty foods in the average American diet are high in bad fat. Those foods include red meat, pizza, pies, pastries, frosted cakes, full-fat ice cream, butter, stick margarine, doughnuts, and most commercially fried foods (chicken, fish, and French fries). So people who mistakenly conclude that they neednít watch their fat intake are likely to eat more bad fat.
Media reports also downplayed an intriguing result in the study on breast cancer. The data suggest that a low-fat diet may reduce the risk of breast tumors that respond to estrogen but not progesterone. Future research may clarify whether diet reduces the risk of some tumors but not others.