Effects of dietary protein on growth and on plasma and liver vitamin A and E levels in young rats

Abstract

The effects of dietary protein sources on rat plasma and liver vitamin A and E levels were studied in male weanling rats fed purified 20% protein diets for 28 days. Diets contained adequate amounts of all vitamins and minerals. The food efficiency values expressed as percentages of ANRC casein ranged from 85 to 99 with the exception of liver powder, which was 45. The liver vitamin A levels ranged from 131 to 320 μg/g. The liver vitamin A levels were higher for soy isolate, soy flour, blue-green algae (BGA) and liver powder than for ANRC casein (P<0.05). The high-lactose whey group had the lowest vitamin A levels; liver powder had the highest. The liver vitamin E levels ranged from 42 to 96 μg/g. The liver vitamin E levels with all protein sources, except wheat-milk and milk-egg-BGA, were lower than for ANRC casein (P<0.05). Liver vitamin E levels for textured soy protein, low-lactose whey and BGA were approximately 47% lower than for soy isolate, high-lactose whey and milk-egg-BGA, respectively. ANRC casein had the highest plasma vitamin A and E levels (P<0.05). Milk-egg-BGA, liver powder and BGA caused the greatest reductions in plasma vitamin E, 48, 59 and 88%, respectively. The results suggest that food processing and/or protein matrices may possibly affect liver and plasma vitamin A and E levels.