The most prominent manifestations of a deficiency of vitamin A include difficulty in adapting to the dark, followed by night-blindness and a serious inflammation of the eyes that may end with loss of sight. Other important changes affect the skin. the deficiency may be due to an insufficient intake of vitamin A or carotene, from which it is formed in the body, or in failure of the body to absorb and utilize these materials. We know now that inflammations of the liver may interfere with the body’s use of vitamin A. Mineral oil taken in large amounts prevents the absorption of vitamin A. The condition affects infants more often than adults, since infants require the vitamin both for growth and maintenance of certain structures. The liver can store enough vitamin A to carry the body along for six to ten months.
The changes in the skin associated with a deficiency of vitamin A include a generalized dryness and the growth of horny plugs called “hyperkeratoses” over the extensor surfaces of the limbs, the back, and the buttocks. Another manifestation is the appearance of grayish-white spots on the white portion of the surface of the eye.
When a shortage of vitamin A is noted, the condition should be corrected immediately by including in the diet such foods as butter, vitamin-enriched margarine and cod liver oil, which provide plenty of vitamin A. If symptoms have occurred, extra vitamin may be given as a capsule containing up to 25,000 units daily, which is about five times the usual required daily intake.
Cases are known in which people have taken tremendous quantities of this vitamin, even up to 250,000 units of vitamin A per day. Large excesses may cause serious changes in the liver, the spleen, the blood and the hair and nails.