The challenge to reach nutritional adequacy for vitamin A: β-carotene bioavailability and conversion-evidence in humans

beta-Carotene is an important dietary source of vitamin A for humans. However, the bioavailability and vitamin A equivalency of beta-carotene are highly variable and can be affected by food- and diet-related factors, including the food matrix, food-processing techniques, size of the dose of beta-carotene, and the amounts of dietary fat, fiber, vitamin A, and other carotenoids in the diet as well as by characteristics of the target population, such as vitamin A status, nutrient deficiencies, gut integrity, and genetic polymorphisms associated with beta-carotene metabolism. The absorption of beta-carotene from plant sources ranges from 5% to 65% in humans. Vitamin A equivalency ratios for beta-carotene to vitamin A from plant sources range from 3.8:1 to 28:1, by weight. Vitamin A equivalency ratios for beta-carotene from biofortified Golden Rice or biofortified maize are 3.8:1 and 6.5:1, respectively, and are lower than ratios for vegetables that have more complex food matrices (10:1 to 28:1). The vitamin A equivalency of beta-carotene is likely to be context-specific and dependent on specific food- and diet-related factors and the health, nutritional, and genetic characteristics of human populations. Although the vitamin A equivalency of beta-carotene is highly variable, the provision of vegetable and fruit sources of beta-carotene has significantly increased vitamin A status in women and children in community settings in developing countries; these results support the inclusion of dietary interventions with plant sources of beta-carotene as a strategy for increasing vitamin A status in populations at risk of deficiency. Am J Clin Nutr 2012;96(suppl):1193S-203S.