In the February 2005 issue of Tufts University Nutrition Newsletter there was a special report on Vitamin A. The main point of the report was to highlight the fact that Vitamin A is toxic, even at doses lower that previously thought. To quote some relavant main points of the article for you: "Scientists have known for decades that in very high doses, Vitamin A is toxic. But now it appears that even moderately high doses---the kind you can get from regularly popping high-dose supplements from health food stores may be harmful to some people". "The line between too much and too little turns out to be a fine one." "We are still in the process of figuring out how big the window is, says Robert Russell, MD, director of the Hean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts. With the exception of certain trace minerals, its boundries appear to be much narrower than almost any other nutrient." "Excess Vitamin A is not easily flushed from the body. Chronic toxicity, while rare, can occur with long-term consumption of 25,000 IU of vitamin A a day. The symptoms, while reversible, are none too pretty: water in the brain, vomiting, tiredness, constipation, bone pain and severe headaches. The skin may acquire a rough and dry appearance and this can be accompanied by hair loss and brittle nails. Vitamin A supplements have also been linked to hip fractures in postmenopausal women increased risk of spontaneous abortion in the first two months of pregnancy. The National Academy of Science has lowered its suggestion for vitamin A, saying men should aim for no more than 3000IU each day while women should strive for 2,330 IU. Even more significant, says Dr. Russell, is that the upper intake level was placed at no more than 10,000 IU. The body can convert beta-carotene into vitamin A in only the amount that it needs." Beta-carotene supplements do seem to have some down sides, especially for smokers. For smokers, high-doses of beta-carotene incresed the incidence of lung cancer. According to Dr. Wang, a researcher at HNRCA, "The beneficial versus harmful effects of beta-carotene are definitely related to the doses we take and the accumulation of the carotenoid in our body. Beta-carotene, like vitamin A, is a fat-soluble compound and can be stored in our organs at a very high level, particularly if you take it for a prolonged period of time. Why? Ironically, the presence of too much beta-carotene led to a complicated chemical process that actually destroys retinoic acid, the most active form of vitamin A that regulates cell function and has been shown to have anti-cancer properties. In other words, too much beta-carotene was interfering with the good qualities of vitamin A. The final paragraph of the special reports contains this recommendation: ...the best advice is to be prudent with supplements. In the United States, there is no reason for a healthy person to take a vitamin A containing supplement. The only people for whom vitamin A-containing supplements are warranted are those who have chronic gastrointestinal disease and therefore have difficulty absorbing nutreints.
Bottom line...from reading what you are taking, it seems safe in that the vitamin A is in the form of beta-carotene. However, remember you are getting some vitamin A from foods, and too much beta-carotene may be interferring with it's effectiveness.
Sue Gilbert, M.S., Nutritionist at iVillage.com
