The lipid theory of cardiovascular disease states that dietary cholesterol and saturated fatty acids cause elevations in plasma levels of cholesterol, and that this in turn is the cause of cardiovascular disease. The assumption that dietary cholesterol and saturated fatty acids are able to cause increases in plasma levels of cholesterol is pivotal to the theory. Certainly dietary cholesterol and saturated fatty acids may influence the cholesterol levels in individuals with familial hypercholesterolaemia, a disorder characterised by excessively high levels of plasma cholesterol that ultimately leads to the development of atherosclerosis at an early age. Indeed, many of the studies that have reported associations between dietary lipid intake and cardiovascular disease in populations as a whole, have not controlled for those with familial hypercholesterolaemia. Removal of such subjects attenuates the association.
When healthy populations are considered, there does not appear to be an association between dietary cholesterol and cardiovascular disease. For example, in one study, the effects of eggs of plasma levels of cholesterol were tested in rural farm workers who received eggs as part of payment for their work and subsequently therefore had a high intake of dietary cholesterol. However, there were no detrimental changes to the plasma levels of cholesterol in the subjects who consumed the high egg diet when compared to control subjects who ate very low levels of cholesterol (here), suggesting their risk of cardiovascular disease was not affected. Studies have also investigated the effects of high intakes of saturated fat on plasma levels of cholesterol and cardiovascular disease in rural populations with high intakes of coconut. The subjects who lived in the Pukapuka and Tokelau in the polynesian atolls and are known for their high intakes of saturated fat but low intakes of sucrose and cholesterol.
A study investigating the islanders showed that the Tokelauans obtained greater energy from coconuts compared to the Pukapuka (63 % compared to 34 %, respectively)1. The higher energy intake resulted in a significantly higher intake of saturated fat in the Tokelauans which was composed primarily of lauric (C12:0) and myristic acids (C14:0). The serum total cholesterol levels were 34 to 40 mg/dL higher in the Tokelauans, who had a larger body size and more body fat than the Pukapukans. As bodyfat levels are associated with cholesterol levels, it is not possible to say that the saturated fat was the reason for the association dietary fat and plasma cholesterol. The higher energy intake of the Tokelauans may also explain the higher plasma cholesterol levels. More importantly the risk of cardiovascular disease was low in both groups of islanders. Therefore high intakes of saturated fat are not the cause of cardiovascular disease, as has been shown in studies investigating the high intakes of saturated fat in the Maasai in Africa.
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