Vitamin A Requirement of Human Adults: An Experimental Study of Vitamin A Deprivation in Man. A Report of the Vitamin A Sub-Committee of the Accessory Food Factors Committee.

This monograph is a description of a long and complicated experimental study on 23 human volunteers, 16 of whom were given a diet virtually devoid of vitamin A and carotene; the remaining 7 received the same diet with a daily supplement of either 2,500 international units of oleovitamin A U. S. P. (natural vitamin A in oil), or 5,000 international units of carotene. The principal laboratory tests used to determine the extent of vitamin A deficiency were measurements of plasma vitamin A and carotenoid content and various tests of retinal function. The latter were the more reliable. Indisputable evidence of deficiency did not appear until after eight months; ultimately, unmistakable deficiency developed in only 3 of the 16 volunteers who persisted in the tests for twelve to twenty-four months.

Follicular hyperkeratosis, conjunctival degeneration and abnormal fatigue were not encountered. After deficiency states were observed, the amounts of vitamin A or