Taking vitamin A supplements can weaken the bones and increase the risk of fractures up to seven times, according to a large Swedish study. The research, conducted on men, confirms three earlier studies in women showing that high intake of vitamin A raises the risk of broken hips and weak bones. The latest study is the first to measure levels of the vitamin in blood, rather than just asking about diet and supplement use.
The three-decade study and other evidence suggest that daily vitamin A consumption of more than 1.5 milligrams can be dangerous, and that most people should not take vitamin A supplements. Current dietary recommendations call for only 0.7 mg of vitamin A for women and 0.9 mg for men a day. That is easily supplied by a healthy diet. But many popular multivitamins contain 0.75 mg to 1.5 mg of vitamin A, generally listed on labels as 2,500 international units and 5,000 IUs, respectively. “Vitamin A is potentially harmful,” said Dr. Donald Louria, chairman emeritus of preventive medicine at the University of Medicine and Dentistry of New Jersey in Newark, N.J. “Unless there is a known medical reason like certain diseases of the eye, people should not be taking vitamin A supplements.”