Part 6: Safety First — Excess
Is a low-carb diet safe? A diet that is lower in carbohydrates is by necessity higher in protein and fat. And everybody knows that’s supposed to be trouble, right? After all, researchers have been focusing on dietary fat and cholesterol for a long, long time as a potential source of cardiovascular disease. But in part, it was because a simple test had been discovered to measure serum cholesterol, and, like the drunk in the old joke, the researchers were looking for their car keys over near the streetlight, where the light was better.
In fact, there wasn’t even a good association between total dietary fat or total serum cholesterol and total mortality. The picture got a little clearer when LDL was considered separately from HDL, but it also made all the old recommendations nonsensical:
The observation that monounsaturated fats both lower LDL ['bad'] cholesterol and raise HDL ['good' cholesterol] also came with an ironic twist: the principal fat in red meat, eggs, and bacon is not saturated fat, but the very same monounsaturated fat as in ['heart-healthy'] olive oil. The implications are almost impossible to believe after three decades of public-health recommendations suggesting that any red meat consumed should at least be lean, with any excess fat removed.
Consider a porterhouse steak with a quarter-inch layer of fat. After broiling, this steak will reduce to almost equal parts fat and protein. Fifty-one percent of the fat is monounsaturated, of which 90 percent is oleic acid [the same fat that comprises olive oil]. Saturated fat constitutes 45 percent of the total fat, but a third of that is stearic acid, which will increase HDL cholesterol while having no effect on LDL (Stearic acid is metabolized in the body to oleic acid, according to Grundy’s research.) The remaining 4 percent of the fat is polyunsaturated, which lowers LDL cholesterol but has no meaningful effect on HDL. In sum, perhaps as much as 70 percent of the fat content of a porterhouse steak will improve the relative levels of LDL and HDL cholesterol, compared with what they would be if carbohydrates such as bread, potatoes, or pasta were consumed. The remaining 30 percent will raise LDL cholesterol but will also raise HDL cholesterol and will have an insignificant effect, if any, on the ratio of total cholesterol to HDL. All of this suggests that eating a porterhouse steak in lieu of bread or potatoes would actually reduce heart-disease risk, although virtually no nutritional authority will say so publicly. The same is true for lard and bacon.
…from Good Calories, Bad Calories (Knopf, 2007), by Gary Taubes, p. 168-169
Continued in Part Seven…