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The structures of the major dietary forms of vitamin A. Preformed retinol is primarily found as retinyl palmitate in most animal livers, fortificants, and supplements. From ∼50 provitamin A carotenoids in plants, the common ones include α-carotene, β-carotene, and β-cryptoxanthin. These forms of provitamin A carotenoids are often quantified in human serum.
