Saturated Fat and Heart Disease: the meta-study
The article opens by pointing out that "Early animal studies showed that high dietary saturated fat and cholesterol intakes led to increased plasma cholesterol concentrations as well as atherosclerotic lesions". However, "More recent epidemiologic studies have shown positive, inverse, or no associations of dietary saturated fat with CVD morbidity and/or mortality". Obviously, these conflicting studies lead us nowhere. They then continue and point out that the studies that showed benefits of saturated fat reduction were those in which the satured fat was replaced by polyunsaturated fat. Possibly, the increase in polyunsaturated fat is the cause of the benefit, rather than the reduction in saturated fat. Either way, this brings up the issue of the replacement for the saturated fat - to make up for the caloric loss, does it make a difference what other type of food intake replaces the decrease in fat calories?
The uniqueness of this study (compared to many other modern studies), is that it looks directly at health impacts, rather than at "risk factors". It analyzes the results based on the number of fatal and non-fatal cardiovascular events (e.g., heart attacks, strokes, etc.) rather than based on changes in cholesterol levels. 19 previous studies were included, that had a 5 to 23 year follow-up, and included 347,747 subjects. Of these subjects, 11,006 developed heart disease or stroke.
The results show no correlation between saturated fat consumption and cardiovascular disease within the Margin of Error. Comparing groups with the highest versus lowest fat consumtion, the relative risk for CHD was 1.07, with a Margin of Error between 0.96 and 1.19; the relative risk for stroke was 0.81 (0.62 to 1.05 Margin of Error); the relative risk for all CVD was 1.00 (Margin of Error between 0.89 and 1.11). The results were not changed by subdividing the subjects by age or sex. They state that the influence of specific replacement nutrients needs more data to be able to arrive at conclusions.
Some of the issues of nutrient replacement are addressed in a subsequent paper (Reference 2), summarized on the next page.