THE INFILTRATION OF CAROTENOIDS INTO H U-

CAROTENOIDS are lipids which are usually colored either red or yellow. In figure 1, the distinguishing characteristics of the carotenoid molecule are illustrated by the specific carotenoid lycopene. Common to all carotenoids is a long central carbon chain which contains a sequence of periodic double bonds and methyl side groups. In certain carotenoids, the ends of this chain are closed rings. Other carotenoids have a hydroxyl group attached to the terminal ring, and may occur in nature either as the free carotenoid alcohol or as the ester of a fatty acid. Carotenoids occur in human tissue as a result of absorption from the intestine of pigments ingested with foodstuffs. There is abundant evidence that carotenoids are not synthesized by any human tissue. Because certain carotenoids serve as precursors of vitamin A, studies have been performed to determine the effect of a carotenoid-free diet in normal man. When carotenoids are omitted from the diet, blood and tissue levels promptly decline, and continue to fall until carotenoids can no longer be detected.1 On the other hand, increased carotenoid intak