Hypervitaminosis A
An overdose of vitamin A may cause serious injury to health. It is most likely to happen when children are given too much of a high-potency supplement. Because watermiscible preparations are better utilized than oily preparations, they are more toxic when intake levels are equal. The symptoms of hypervitaminosis A are loss of appetite, abnormal skin pigmentation, loss of hair, dry skin (with Iching), pain in the long bones, and increased fragility of the bones in general. Regular supplementation of more than 3000 RE (10,000 IV) of retinol above that consumed the diet should be carefully supervised by a physician. In adults, regular daily ingestion of more than 7500 RE 25,000 IV) is not advisable.
In three cases of adolescent girls reported, 28 massive doses of 90 ,000 and 200 ,000 IU of vi:tamin A caused symptoms of brain tumor (pseudoumor cerebri), along with most of the syndrome deocribed above.
It now appears that vitamin A toxicity develops when the capacity of the liver to store the vitamin is exceeded.Normally, retinyl esters are mobilized from the liver as rerinol bound to REP, and only a small fraction of total circulating vitamin A is in the ester form. In hyper-:raminosis the proportion of total plasma vitamin A as :-erinyl ester found in association with the low-density lipoproteins is greatly increased. This nonspecifically bound vitamin is believed to be toxic to cellular mem:-anes due to its surface-active properties.
Carotene in large doses is not toxic but usually causes a yellow colora tion of the skin which disappears when the otene is discontinued.
