Dietary vitamin E and beta-carotene sources influence vitamin A and E storage in young rats fed marginal and adequate vitamin E

The effects of two vitamin E levels (30 and 75 IU/kg diet) and the interrelation of two vitamin E sources [dl-alpha-tocopheryl acetate (dl-alpha-TA) and d-alpha-tocopheryl acid succinate (d-alpha-TAS)] and three vitamin A sources [retinyl palmitate (RP), all-trans synthetic beta-carotene (SBC), and natural beta-carotene (NBC)] were studied. Dietary vitamin A sources provided 4,000 IU/kg. Twelve groups of Fischer 344 rats (10/group) were fed designated diets for eight weeks. For RP, SBC, and NBC, the increase in each vitamin E source from a marginal to an adequate dietary level caused a significant increase in liver and heart alpha-tocopherol. Among rats fed diets with an adequate level of vitamin E, d-alpha-TAS was not as effective as dl-alpha-TA in increasing liver alpha-tocopherol levels. Plasma retinol was lower in rats fed d-alpha-TAS than in those fed dl-alpha-TA. Among rats fed diets with an adequate level of dl-alpha-TA, those fed SBC had significantly higher liver and heart alpha-tocopherol concentrations than did all other groups (p < 0.05). Liver retinol equivalents for rats fed NBC were approximately 66% lower than those in rats fed SBC or RP (p < 0.05). The roles of the two vitamin E sources in alpha-tocopherol metabolism are not equivalent. These data indicate that vitamin A source influences the magnitude of the tissue vitamin A and E changes in response to the two vitamin E sources.