Vitamins A, E, and carotene: effects of supplementation on their plasma levels.

We conducted a randomized, double-blind trial among 59 generally well-nourished adults to determine the effects of vitamin A, vitamin E, and beta-carotene supplements on plasma retinol, alpha-tocopherol, and carotenoid levels. Over a period of 16 wk a daily alpha-tocopherol supplement of 800 IU approximately doubled plasma alpha-tocopherol levels (p less than 0.001), caused a small decrease in plasma carotenoids (p = 0.02), and produced a slight and statistically insignificant reduction in plasma retinol. A daily beta-carotene supplement of 30 mg (5000 retinol equivalents) approximately tripled plasma carotenoid levels (p less than 0.001) but did not affect plasma retinol or alpha-tocopherol. A daily retinyl palmitate supplement of 25,000 IU (13,750 retinol equivalents) did not appreciably affect plasma retinol, alpha-tocopherol, or carotenoid.