There has been much discussion about the safe dosages of vitamin A. The Recommended Dietary Allowances (RDA) have frightened consumers, and the government has not published the facts about vitamin A. In the first place, vitamin A or retinol is the form of vitamin A found in animal tissue. Carotene is the form of provitamin A found in plant tissue. The RDA claims that levels higher than 5000 IU of vitamin A may be toxic in human males, yet dosages of prepared vitamin A are between 10 000 and 25 000 IU (depending on the country the product is sold in). The controversy has arisen from the therapeutic use of vitamin A in the treatment and prevention of diseases such as cancer. Reactions that occur from long-term use of high doses of vitamin A may include dry skin, headaches, and fatigue, and have been observed clinically when doses of over 100 000 IU a day have been taken for approximately 13 months. But all symptoms disappeared following discontinuation of the supplement. Other studies have shown that it took 71/2months for symptoms of toxicity to develop after consumption of 300 000 IU a day. However, no toxic effects have been observed in people taking 50 000 IU a day over a long period of time. Thus, vitamin A shows no toxic side effects at levels 10 times the RDA.
Although experts are still debating the optimum level of vitamin A, one 1976 study suggests that the "ideal" daily allowance of vitamin A is 33,000 IU. New studies on the benefits of vitamin A are appearing in the scientific literature every year, which no doubt will alter the "ideal" daily allowance of vitamin A.
if you are still worried about taking vitamin A but want a supplement, take beta carotene, the nontoxic vitamin A precursor, also known as provitamin A.
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