Too Much Vitamin A Boosts
Risk of Broken Bones

NEW YORK (Reuters Health) - Men in their 40s and 50s who have the highest blood levels of vitamin A are more likely to break a bone in their old age than their peers with lower levels, according to a Swedish study released Wednesday.

The results--which confirm two other studies in women--suggest that some people may be getting too much of a good thing via supplements and fortified food, the study's authors say.

They believe that "current levels of vitamin A supplementation and food fortification in many Western countries may need to be reassessed," according to the report.

Dr. Karl Michaelsson of University Hospital in Uppsala, Sweden and colleagues looked at 2,322 men aged 49 to 51 and followed them for 30 years. Men with the highest blood levels of vitamin A at the beginning of the study were 1.6 times as likely to break a bone as men with an average amount of vitamin A in their blood. When it came to breaking a hip, those with elevated vitamin A had a 2.5-fold greater risk than men with lower levels of vitamin A. Overall, 266 men broke a bone during the study.

There was no link between blood levels of beta-carotene, a compound that is converted to vitamin A in the body, and fracture risk, according to the report in the January 23rd issue of the New England Journal of Medicine.

Vitamin A is found in fish liver oils, liver, kidney and milk. It is sometimes added to dairy products, which in Sweden includes margarine and low-fat dairy products.

While vitamin A is necessary for growth, vision, reproduction and a healthy immune system, too much vitamin A has long been known to be dangerous. Taking too much vitamin A (25,000 IU to 50,000 IU per day or more) over long periods can cause bone and joint pain, loss of appetite, nausea, vomiting and weight loss.

And a single extremely high dose can cause drowsiness, irritability, headache, vomiting and widespread peeling off of the skin.

In an accompanying editorial, Dr. Paul Lips of Vrije Universiteit Medical Center in Amsterdam, The Netherlands, notes that blood levels of vitamin A tend to increase with age, probably because it takes longer to clear from the body.

The risk of too little vitamin A is greatest in malnourished children and the risk of too much is greatest for adults--especially older people, Lips notes.

The current study "suggests that vitamin A supplementation and fortification of food with vitamin A may be harmful in Western countries, where the life expectancy is high and the prevalence for osteoporosis is increasing."

SOURCE: The New England Journal of Medicine 2003;348:287-294,347-349.

Reference Source 89

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