Excess Vitamin A Leads to Fractures
A recent study published in the New England Journal of Medicine indicates that middle aged men with high blood levels of vitamin A are more likely to break a bone in the later years of their life compared to those with lower levels of the vitamin. In a population based study, these investigators monitored 2,322 men aged 49 to 51, for 30 years. Serum retinol and beta carotene were analyzed at study enrollment. During the follow up period, fractures were documented in 266 individuals and the risk of fracture was measured according to the serum retinol level. Men with the highest levels of vitamin A were found to be 2.5 times more likely to break a bone than men with lower levels of vitamin A. There was no link between blood levels of beta carotene and fracture risk. The investigators suggested re-evaluation of current levels of vitamin A supplementation and food fortification.
Chronic vitamin A toxicity, caused by high intake of vitamin A over a long period, is known to result in bone and joint pain, anorexia, nausea and vomiting and weight loss. High levels of vitamin A are also known to affect bone and mineral metabolism. It has also been reported that the relative risk of bone fracture was 2.1 for persons with vitamin A intake exceeding 1.5 mg/day compared to those whose intake was less than 0.5 mg/day.
Serum retinol levels may increase with age, probably as a result of decreased ability of the body to clear such substances, thus increasing the risk of older people taking excessive vitamin A.