Why didn't the WHI study indict saturated fat?

The Women's Health Initiative (WHI) probably found that a low-fat diet doesn't prevent coronary heart disease in postmenopausal women because, among other reasons, the study did not target specific kinds of fat.

The dietary modification arm of WHI studied almost 49,000 postmenopausal women for 8 years. About 40% of them got intensive behavioral interventions to reduce fat to 20% of calories and increase intake of fruits, vegetables, and grains. As reported in the February 8 issue of JAMA, the lower-fat diet did not significantly reduce the risk of coronary heart disease, stroke, or cardiovascular disease (combined CHD and stroke) "and achieved only modest effects on CVD risk factors, suggesting that more focused diet and lifestyle interventions may be needed to improve risk factors and reduce CVD risk."

Linda Van Horn, PhD, RD, speaking at an NIH-sponsored conference entitled "The WHI Legacy to Future Generations of Women" (February 28–March 1, 2006) pointed out that the study's first goal was to test whether lowering overall fat intake would reduce breast cancer, and thus: "Saturated fat did not command the greatest attention in terms of the overall intervention."

In addition she noted that there was no separate focus on trans fats, because when the study was launched there was little known about them. Van Horn also stressed that the study did show, "decreased risk for those who adhered most to the reduction in saturated fat and trans fat and increased the most in fruits and vegetables."

"There were no changes in triglycerides, HDL cholesterol, glucose, or insulin, and interestingly, those factors are typically most associated with changes in weight," she said. Weight change itself was not a major study focus, said Van Horn, so that leaves questions unanswered.