Postprandial lipid metabolism: effects of dietary fatty acids.

Current dietary recommendations for fatty acid intakes aimed at reducing the prevalence of CHD are largely based on the cholesterol hypothesis and on the well-established effects of specific fatty acid classes on fasting total cholesterol, LDL and HDL concentrations (Department of Health, 199 1, 1994). Increasing recognition of the potential atherogenic and thrombogenic consequences of elevated triacylglycerol-rich lipoproteins (TRL; Cohn, 1994; Havel, 1994; Karpe et al. 1994; Hodis & Mack, 1995; Karpe & Hamsten, 1995) has revealed the paucity of dietary studies which evaluate postprandial as well as fasting lipoproteins. The need for a greater understanding of effects of diet on postprandial lipoproteins is emphasized by the fact that most individuals are in a postprandial state for the greater part of every 24 h period. A typical 24 h triacylglycerol profile of a normal individual eating three or four meals and snacks per day is shown in Fig. 1, and illustrates that triacylglycerol levels are elevated above fasting values for approximately 17 h of each 24 h period. Only in the early morning between 03.00 and 06.00 hours, do triacylglycerol levels reflect the values measured after a 12 h fast, the measurement usually made in most epidemiological studies. It is clear that the fasting state does not reflect total 24 h triacylglycerol values and is not the normal nutritional state for most individuals, at least as far as lipid metabolism is concerned.