Cereal Chem 63:490-493   |  VIEW ARTICLE
Bioavailability of Vitamins A and E as Influenced by Wheat Bran and Bran Particle Size.

T. S. Kahlon, F. I. Chow, J. L. Hoefer, and A. A. Betschart. Copyright 1986 by the American Association of Cereal Chemists, Inc. 

The effect of wheat bran and bran particle size on the bioavailability of vitamins A and E was investigated in diets containing 5.7-10.7% dietary fiber. Fifty-six male weanling Sprague-Dawley rats were randomly assigned to four diets containing 5% cellulose (C5), 10.5% cellulose (C10), 21.5% coarse (2-mm) wheat bran (CB), or 22.2% fine (0.5-mm) wheat bran (FB) in a six-week study. At the end of six weeks, plasma retinol values were significantly higher in rates fed C10 than those fed C5 and CB diets (0.38 vs. 0.31 and 0.32 microgram/ml, respectively). Also after six weeks, liver retinyl palmitate was significantly higher in rats consuming high-fiber diets. These data indicate that dietary fiber did not adversely influence liver storage of vitamin A. Plasma values did not consistently reflect liver status for either vitamins A or E. Liver alpha-tocopherol values were significantly lower in rats fed CB than those fed FB and C10 diets (39.24 vs. 44.04 and 44.03 micrograms/g, respectively), suggesting that CB significantly decreased bioavailability of alpha-tocopherol as compared to FB or C10 diets when fed similar levels of dietary fiber. Similar liver vitamin E values with fine bran and high-cellulose diets indicate that the vitamin E in wheat bran was not readily available. Data further suggest that coarse bran also reduced availability of the vitamin E in the diet. The significant impairment in bioavailability of vitamin E by coarse bran compared to fine bran indicated that this impairment may not be a function of adsorption of vitamin E on the surface of bran particles. The effect of CB may be partly caused by its interaction and effect on the morphology and physiological processes of the intestinal lumen and its absorption sites.