The effect of fish oil supplementation on plasma alpha-tocopherol, retinol, lipid and lipoprotein levels in normolipidemic subjects

The effects of supplementation with maxEPA fish oil (FO) on the plasma concentrations of alpha-tocopherol, retinol, lipids and lipoproteins in young male subjects were studied. Ten normolipidemic adult male volunteers (25-39 y) supplemented their usual Western diets for 6 wk with 18 g MaxEPA FO per d. Blood samples were collected prior to supplementation, after 6 wk of supplementation, and 10 wk following cessation of the supplement. There was a significant increase (21%) in plasma alpha-tocopherol concentration after 6 wk of FO supplementation which returned to baseline 10 wk after cessation of the supplements. Plasma retinol increased by 14% and plasma triglyceride (TG) concentration decreased by 28% after 6 wk of supplementation. When FO was taken as a supplement to a typical Western diet significant increases in the concentrations of total cholesterol (TC) (7%), low-density-lipoprotein cholesterol (LDL-C) (10%) and high-density-lipoprotein (HDL-C) (10%) in normolipidemic subjects were observed. Despite animal data indicating an increased need for dietary vitamin E with FO supplementation, in this clinical trial, the FO supplement administered in this study increased plasma alpha-tocopherol. This increase is due to the 1.35 mg of alpha-tocopherol added by the manufacturer which appears sufficient to maintain plasma vitamin E levels in the presence of increased PUFA intake, at least over a 6 wk period. Retinyl ester content in eight commercial FO products other than MaxEPA ranged from 2 to 2450 micrograms/g FO, with a mean of 315 micrograms/g. The alpha-tocopherol content in 12 other FO capsules available to consumers for over the counter purchase ranged from 18 to 2241 micrograms/g FO, with a mean of 1025 micrograms/g. The effects of ingesting FO supplements with a low content of alpha-tocopherol on the plasma levels of alpha-tocopherol needs to be further examined.