Robert Russell, professor of medicine and nutrition, Tufts University School of Medicine, Boston, and chair of the panel that wrote the recently released report on vitamin A by the National Academy of Sciences (NAS), says there is absolutely no danger of toxicity from the beta carotene form of vitamin A often provided in daily multivitamins. Beta carotene is converted to vitamin A in the liver, and excesses are stored in the skin.
The NAS report on vitamin A, which has been widely publicized in the news media, has caused thousands of vitamin supplement users to call manufacturers regarding potential vitamin A toxicity. Dr. Russell, says the danger of liver toxicity is only posed by vitamin A acetate and palmitate, fatty forms of vitamin A, that may build up in the liver. People can take 50,000 international units of vitamin A from beta carotene without toxicity, says Dr. Russell.
According to Dr. Russell, there have no reported cases of toxicity at the 10,000 IU intake of vitamin A, but to be on the safe side, the National Academy of Sciences establishes a 5X safety factor. In a recent study involving 146 patients who took an average of 18,000 units of vitamin A palmitate over a 5-year period as treatment for inherited night blindness, none developed liver toxicity.
Dr. Russell notes that while there are few cases of overt vitamin A deficiency resulting in night blindness in the USA, one study indicates 25-50 percent of young adults may not have sufficient stores of vitamin A in the liver. He says the NAS indicates healthy adults should have a 4 months-supply of vitamin A stored in their liver.
Very high-dose beta carotene sometimes results in a harmless orange skin condition called carotenemia that can even fool doctors into thinking a person has jaundice.
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