Postprandial changes in the plasma concentration of alpha- and gamma-tocopherol in human subjects fed a fat-rich meal supplemented with fat-soluble vitamins

Abstract

The plasma concentrations of alpha (alpha)- and gamma (gamma)-tocopherol in 10 male and 15 female subjects (n = 14) received 1 g fat/kg body wt as soybean oil, and the meal was supplemented with 100% of the RDA for fat-soluble vitamins. In expt. 2, the subjects (n = 11) received 1 g fat/kg body wt as 50% soybean oil + 50% cream, and the meal was supplemented with 200% of the RDA for fat-soluble vitamins. The ratio of gamma- :alpha-tocopherol given in the test meal of expt. 1 was 2.8:1 and in expt. 2 was 0.9:1. Blood samples were obtained 0, 3, 6, 9 and 12 h after the meal. Tocopherol concentration was measured in plasma and lipoprotein fractions. In both studies, plasma triglyceride concentration increased significantly after the meal (P less than 0.001). Mean plasma cholesterol and alpha-tocopherol concentrations were unchanged, but plasma gamma-tocopherol concentration was significantly increased at 6, 9 and 12 h after the meal (P less than 0.05). The increase in plasma gamma-tocopherol was due to increases within the triglyceride-rich lipoprotein (TRL) fraction (d less than 1.006 g/ml) at earlier timepoints, followed by a sustained increase within low density lipoprotein (LDL) and high density lipoprotein (HDL) fractions at later timepoints. In contrast, alpha-tocopherol in LDL and HDL decreased postprandially, concomitant with a rise in TRL alpha-tocopherol. Our results are consistent with the concept that there are differences in the distribution of alpha- and gamma-tocopherol in postprandial lipoproteins.