Cholesterol Skeptics
Weintraub's Response
A response to Ravnskov's review was provided by Dr. William Weintraub who is currently a professor of cardiology at Emory University. Dr. Weintraub begins by stating the plausibility claim - if one's diet raises cholesterol, and high cholesterol indicates a higher risk of CHD, it is reasonable to expect that if one eats a poor diet for decades, one will develop the disease. He then discusses at length the possible processes by which cholesterol can give rise to atherosclerosis and inflamation. This leads to a requirement to mitigate the risk by reducing cholesterol. Concerning the seemingly high risk associated with very low cholesterol, he states that this is probably due to "confounding" - that is, the low readings were due to illnesses that preceded the study. In addition, he references a major study in the elderly that does show a rise in risk with high cholesterol.
Dr. Weintraub then turns to the issue of whether lowering cholesterol by medication impacts the risk for heart disease. Certainly statins lower the risk, while also lowering cholesterol. However, it is possible that the mechanism for lowering the risk involves lessening the inflamation in the arteries, and is not a direct consequence of cholesterol lowering. Therefore he quotes other studies involving surgery of taking gemfibrozil (a medication) that reduce cholestrol. In general, these studies seem to find that after two years or more of reduction, there is a reduction in myocardial infarction rates and in death from coronary causes. However, in most studies, there is no difference in death from any cause.
Dr. Weintraub then points out that since the mid-1960s, the rate of CHD deaths has declined, and that is in parallel with the replacement of fat from animal sources (saturated fat) with fat from vegetable sources (unsaturated). He then lists some studies that do show a reduction in cardiovascular diseases and atherosclerosis when saturated fat is replaced with unsaturated fat. Although not directly relevant to this issue, he reminds us that omega-3 fatty acids (fish oil) decrease the incidence of sudden heart failure. Likewise, there are studies such as those that we have reviewed that show a reduced risk when vegetables and fruit, or a Mediterranean diet are consumed. Finally, he notes that if a shift from a fatty diet to a higher-calorie high-carbohydrate diet results in increased obesity, inevitably the risk of CVD will increase.