Minimum Vitamin A Requirements in Infants as Determined by Vitamin A Concentration in Blood.

In previous communications 1 we reported that the vitamin A concentration in the blood is a good indicator of the size of the vitamin A stores in the rat. Thus, low levels of the vitamin in the blood were usually associated with little or no storage in the liver, the chief depot of vitamin A, whereas high concentrations in the blood were accompanied by large stores. Intermediate blood values were of less significance as they were associated with either small or large amounts of vitamin A in the liver.

Studies carried out in infants 2 coincided, in general, with the results of our experiments in rats and indicated the practical importance of the vitamin A blood level in the diagnosis of vitamin A deficiency. In a series of 93 normal infants, ranging in age from 3 weeks to 6 months, the lowest concentration of vitamin A in the blood was found to be 45 international units per 100 cc plasma. Further observations have indicated that 40 international units may be regarded as the lower limit of the normal range of the vitamin A concentration of the blood for infants under 6 months of age. Values below this level were obtained in infants who, either were suffering from disorders interfering with the absorption of the vitamin as, for example, cystic fibrosis of the pancreas, coeliac disease and congenital obliteration of the bile ducts, or were receiving diets devoid of vitamin A.

Required to bring about normal blood levels in young infants having low concentrations of the vitamin in the blood as a result of a diet devoid of vitamin A.