Dietary Antioxidants Affect Vitamin E Isomer Absorption

MARSEILLE, France—Some antioxidants consumed through the diet may adversely impact the intestinal absorption of alpha-tocopherol, a fat-soluble isomer of vitamin E, according to researchers at Méditerranée Aix-Marseille University (Eur J Clin Nutr. 2007;61:1167-73). They first evaluated the effect of different combinations of antioxidants on alpha-tocopherol absorption by a human intestinal cell line, and then compared the effect of two doses of lutein on postprandial alpha-tocopherol responses to an meal rich in that vitamin E isomer. Eight healthy men ate two similar meals in a random order at a one-month interval. The meals contained 24 mg alpha-tocopherol in sunflower oil, plus either 18 or 36 mg lutein. Blood samples were collected during the postprandial periods to compare chylomicron alpha-tocopherol responses.

Researchers found a mixture of polyphenols and a mixture of carotenoids significantly impaired alpha-tocopherol absorption. The inhibitory effect of gamma-tocopherol was close to significance (P=0.055). In contrast, vitamin C had no significant effect (P=0.158). Naringenin was the only polyphenol that significantly impaired alpha-tocopherol absorption. Postprandial alpha-tocopherol response was weakest at the highest dose of lutein (616 ± 280 nmol/l h vs 1001 ± 287 nmol/l h). The observed extent of reduction (-38%, P=0.069) supported the inhibitory effect of carotenoids.