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What if Saturated Fat is Not the Problem?

A professor of biochemistry provides perspective.

By Richard Feinman

Here's an idea to chew on: The carbs in your diet tell your body what to do with the fat you eat, so it's the type and amount of carbohydrates that matter when it comes to your weight and health.

Virtually every bit of health information today includes the advice to avoid saturated fat — the so-called evil stuff that lurks in animal foods like steak and eggs. The basis for this recommendation is that research has shown a correlation between saturated fat intake and total cholesterol and LDL ("bad cholesterol"). The problem with these studies is that the effects are not large, there is wide variation among individuals and, in most of these studies, the predicted benefit in incidence of cardiovascular disease did not materialize. In addition, we now know much more about risk factors for cardiovascular disease (CVD) beyond LDL. No assessment of CVD risk can be made without considering HDL ("good cholesterol"), triglycerides, and the size of the LDL particle. Plenty of research shows that these markers can worsen when people reduce their intake of saturated fat and that they can improve by reducing the intake of carbohydrates.

You don't have to be a medical researcher to recognize that this is a politically charged issue. The thing that is missing for the public is an impartial evaluation of all the data on saturated fat. My personal opinion is that there is much contradictory data and a recent review of the situation suggests that there is not sufficient evidence to make any recommendations.

There is a sense that, in the absence of definitive evidence, lowering saturated fat will at least do no harm. This is not right. The problem for people with diabetes is what happens when saturated fat is replaced with carbohydrate, and research has repeatedly shown that this may actually be harmful. Consider that, according to the Centers for Disease Control and Prevention, during the onset of the current epidemic of obesity and diabetes, almost all of the increase in calories in the American diet has been due to carbohydrate. The percent of total fat and saturated fat in our diet decreased. In men, the absolute amount of saturated fat consumed decreased by 14 percent!

One of the most striking reasons to doubt the across-the-board proscriptions against saturated fat is the report from the large scale Framingham study in the Journal of the American Medical Association, titled "Inverse association of dietary fat with development of ischemic stroke in men." You read that right: The more saturated fat in the diet, the lower the incidence of stroke.

Perhaps the most compelling research was published in a 2004 issue of the American Journal of Clinical Nutrition by researchers from the Harvard School of Public Health. Their study showed that, in postmenopausal women with heart disease, a higher saturated fat intake was associated with less narrowing of the coronary artery and a reduced progression of disease. Even with similar levels of LDL cholesterol, women with lower saturated fat intake had much higher rates of disease progression. Higher saturated fat intake was also associated with higher HDL (the "good" cholesterol) and lower triglycerides.