Connecting to my past few posts regarding fat, cholesterol, and heart disease, Gary Taubes in “The Soft Science of Dietary Fat” from Science, Vol 291, 30 March 2001, writes:
“The original simple story in the 1950s was that high cholesterol levels increase heart disease risk. The seminal Framingham Heart Study, for instance, which revealed the association between cholesterol and heart disease, originally measured only total serum cholesterol. But cholesterol shuttles through the blood in an array of packages. Low-density lipoprotein particles (LDL, the “bad” cholesterol) deliver fat and cholesterol from the liver to tissues that need it, including the arterial cells, where it can lead to atherosclerotic plaques. High-density lipoproteins (HDLs, the “good” cholesterol) return cholesterol to the liver. The higher the HDL, the lower the heart disease risk. Then there are triglycerides, which contain fatty acids, and very low density lipoproteins (VLDLs), which transport triglycerides.
“All of these particles have some effect on heart disease risk, while the fats, carbohydrates, and protein in the diet have varying effects on all these particles. The 1950s story was that saturated fats increase total cholesterol, polyunsaturated fats decrease it, and monounsaturated fats are neutral. By the late 1970s–when researchers accepted the benefits of HDL—they realized that monounsaturated fats are not neutral. Rather, they raise HDL, at least compared to carbohydrates, and lower LDL. This makes them an ideal nutrient as far as cholesterol goes. Furthermore, saturated fats cannot be quite so evil because, while they elevate LDL, which is bad, they also elevate HDL, which is good. And some saturated fats—stearic acid, in particular, the fat in chocolate–are at worst neutral. Stearic acid raises HDL levels but does little or nothing to LDL. And then there are trans fatty acids, which raise LDL, just like saturated fat, but also lower HDL. Today, none of this is controversial, although it has yet to be reflected in any Food Guide Pyramid.
“To understand where this complexity can lead in a simple example, consider a steak—to be precise, a porterhouse, select cut, with a half-centimeter layer of fat, the nutritional constituents of which can be found in the Nutrient Database for Standard Reference at the USDA Web site. After broiling, this porterhouse reduces to a serving of almost equal parts fat and protein. Fifty-one percent of the fat is monounsaturated, of which virtually all (90%) isoleic acid, the same healthy fat that’s in olive oil. Saturated fat constitutes 45% of the total fat, but a third of that is stearic acid, which is, at the very least, harmless. The remaining 4% of the fat is polyunsaturated, which also improves cholesterol levels. In sum, well over half—and perhaps as much as 70%—of the fat content of a porterhouse will improve cholesterol levels compared to what they would be if bread, potatoes, or pasta were consumed instead. The remaining 30% will raise LDL but will also raise HDL. All of this suggests that eating a porterhouse steak rather than carbohydrates might actually improve heart disease risk, although no nutritional authority who hasn’t written a high-fat diet book will say this publicly.”
Taubes is one of my favorite health writers. I highly recommend his Good Calories, Bad Calories and Why We Get Fat. The former is the more demanding read while the latter is a reader-friendly version of the material he covers in the first book. Also, the link in the first paragraph will bring you to Taubes’ article page at his website. Like his books, all are worth a read.