Immune function: relationship of nutrition and disease control. Vitamin A and beta-carotene on host defense.

Even though the protective role played by vitamin A and beta-carotene against numerous diseases has been clearly demonstrated, the exact mechanism by which they afford this protection is not completely understood. Impairment of the animal's immune system resulting from the vitamin deficiency may account for increased susceptibility to infection. This article attempts to draw from available information on the effects of vitamin A and beta-carotene on specific and nonspecific host defense mechanisms as they relate to disease.