Evolution, Cholesterol, and Low-Fat Diets
To the Editor:
Steinberg et al1 report that cholesterol, even at levels within the normal range, may cause endothelial dysfunction. This is hardly surprising. From an evolutionary perspective, which enhances the understanding of both human nutritional requirements2 and humankind’s metabolic physiology,3 there is no doubt that current standards for serum cholesterol values fail to match those of today’s hunter-gatherers, “whose experience represents the closest living approximation of ‘natural’ human lipid metabolism.”4 Whereas in Western countries serum cholesterol levels <200 mg/dL are considered “desirable,”4 the mean serum cholesterol level found in 5 hunter-gatherer groups was 123.2±7.2 mg/dL,4 which suggests that the “desirable” level for serum cholesterol concentration is <150 rather than <200 mg/dL.4 This suggestion, notably, is in accord with the results of Steinberg et al.1 However, although these authors correctly point out that their findings have important clinical implications,1 they unfortunately fail to mention the most important recommendation that can easily be inferred from their study, namely, a drastic reduction in the currently widely advocated direction that 30% of energy should be obtained as fat.5 Such a drastic reduction, besides being theoretically well founded on evolutionary grounds,2 3 4 5 has been experimentally shown to represent an excellent tool for both lowering cholesterol levels and reversing coronary atherosclerosis.5
In view of the frequently reported association between low serum cholesterol and cancer, some physicians might be reluctant to recommend a substantial reduction in dietary fat. Their worries, however, are clearly unjustified, because no enhanced cancer mortality is seen in populations with low cholesterol levels.2 3 4 5 It is evident, therefore, that catabolic diseases cause low cholesterol levels instead of the reverse. On the other hand, it is conceptually untenable that humans can be killed by the same low-fat nutritional environment that both molded their lipid metabolism and kept their cholesterol levels physiologically low for millions of years.2 3 4 5
- Copyright © 1999 by American Heart Association
Steinberg HO, Bayazeed B, Hook G, Johnson A, Cronin J, Baron AD. Endothelial dysfunction is associated with cholesterol levels in the high normal range in humans. Circulation. 1997;96:3287–3293.
Eaton SB, Eaton SB III, Konner MJ, Shostak M. An evolutionary perspective enhances understanding of human nutritional requirements. J Nutr. 1996;126:1732–1740.
Baschetti R. The low fat/low cholesterol diet. Eur Heart J. 1997;18:1514–1515.
We appreciate Dr Baschetti’s comments in response to our publication in Circulation. The aim of our study was to extend to subjects who exhibit “normal range” cholesterol levels the observation that frankly hypercholesterolemic subjects display endothelial dysfunction. Our article was not intended to lead to nutritional guidelines. Clearly, cholesterol contributes to the development of macrovascular disease, and thus, a left shift in cholesterol levels on a population basis is desirable and should lead to lower rates of cardiovascular mortality. However, one needs to be cautious about assigning any teleologic significance to cholesterol levels achieved by primitive diets. Indeed, life expectancy is higher in industrialized populations compared with hunter-gatherers or populations of underdeveloped countries. Although advances in sanitation and disease prevention are undoubtedly important, it is conceivable that higher cholesterol levels than those exhibited by hunter-gatherer populations may confer some survival benefit. Thus, more research on the overall health consequences of different diets must be performed before we should recommend more drastic changes in the diet of healthy people than those already recommended by the AHA or similar organizations.