Sufficient amounts of vitamin A can be obtained through a balanced diet, but vitamin A deficiency can occur due to insufficient intake.[1][2][3] Supplementation with vitamin A is used to treat vitamin A deficiency, which is most common in malnourished infants/children living in developing countries.[1][2][3] The evidence shows that supplementation with vitamin A can improve growth, vision, and survival in malnourished infants/children[4][5][6][7][8][9] and in premature babies.[10][11] However, the precise recommendations for treating vitamin A deficiency are unclear because results are inconsistent among studies.[5][6][7][8][9][10][11]
Observational studies show that higher dietary intake of vitamin A, which includes total vitamin A intake from all sources (foods, drinks, and supplements), is associated with a reduced risk of depression.[12] However, this association is derived from cross-sectional and cohort study designs in which vitamin A intake was estimated from historical diet recall using food frequency questionnaires. This makes it difficult to prove a causal link between vitamin A intake and depression.
Besides dietary vitamin A, all-trans retinoic acid (Tretinoin) and 13-cis-retinoic acid (Isotretinoin) are types of vitamin A used in prescription drugs that are effective in treating acne.[13][14][15]