Vitamin E in foods from high and low linoleic acid diets

Abstract

As part of a human diet study, vitamin E activity was estimated in foods used in seven daily menus. Each menu was designed to contain 35% fat calories with either 10 or 30 gm/day of linoleic acid (18:2) and 500 mg/day of cholesterol. To estimate vitamin E activity, each food used in the menus was analyzed for alpha and gamma tocopherol content by high-pressure liquid chromatography with fluorescence detection. This article reports the alpha and gamma tocopherol contents of those foods, tocopherol contributions from each food in one sample 2,400-kcal menu, and the mean daily vitamin E activity (milligram alpha tocopherol equivalents) of all seven menus at five caloric levels. Major sources of alpha tocopherol (greater than 10% of the RDA) common to both diets (10 and 30 gm linoleic acid) were olive oil and a few fruits and vegetables. Additional major sources in the 30-gm linoleic acid diets were polyunsaturated fatty acid (PUFA) vegetable oils and margarine. Contrary to a common assumption, increasing the level of PUFA in the menus did not necessarily result in higher milligram equivalents of alpha tocopherol because soybean oil, with a tocopherol composition that is predominantly gamma tocopherol, was the major source of linoleic acid in the diets. Thus, vitamin E activity was not necessarily increased when soybean oil was substituted for a less saturated fat such as olive oil, which has mostly alpha tocopherol.