From Reuters Health Information
By Amy Norton
NEW YORK (Reuters Health) Aug 05 - A daily vitamin D supplement may help young men enjoy more sick-free days during cold and flu season, a small study suggests.
Vitamin D has been the subject of much research of late, with studies linking low vitamin D levels in the blood to higher risks of type 1 diabetes and severe asthma attacks in children and, in adults, heart disease, certain cancers and depression.
But whether vitamin D is the reason for the excess risks -- and whether taking supplements can curb those risks -- has yet to be shown.
Because rates of vitamin D insufficiency rise during the winter in many parts of the world, researchers have been interested in whether the vitamin might play a role in people's susceptibility to colds, flu and other respiratory infections.
Some past research has indeed found that people with relatively lower vitamin D levels tend to have higher rates of respiratory infections, said Dr. Ilkka Laaksi of the University of Tampere in Finland, the lead researcher on the new study.
Along with that evidence, recent lab research has shown that vitamin D may play an important role in the body's immune defenses against respiratory pathogens, Dr. Laaksi told Reuters Health by e-mail.
For the current study, reported online July 15th in the Journal of Infectious Diseases, Dr. Laaksi's team randomly assigned 164 male military recruits to take either 400 IU of vitamin D or placebo every day from October to March.
At the end of the study, the researchers found no clear difference between the two groups in the average number of days missed from duty due to a respiratory infection -- which included bronchitis, sinus infections, pneumonia, ear infections and sore throat.
On average, men who took vitamin D missed about two days from duty because of a respiratory infection, compared with three days in the placebo group. That difference was not significant in statistical terms.
However, after adjustment for smoking status, flu vaccination, and other factors, the hazard ratio for absence from duty due to respiratory illness was lower in men who took vitamin D.
The findings, Dr. Laaksi said, offer some evidence of a benefit from vitamin D against respiratory infections.
Still, the extent of the benefit was not clear. While recruits in the vitamin group were more likely to have no days missed from duty, they were no less likely to report having cold-like symptoms at some point during the study period.
Moreover, recent studies on the usefulness of vitamin D for warding off respiratory ills have come to conflicting conclusions.
A study of Japanese schoolchildren published earlier this year found that those given 1,200 IU of vitamin D each day during cold and flu season were less likely to contract influenza A compared to children taking placebo.
On the other hand, a recent study of 162 adults found that those who took 2,000 IU of vitamin D everyday for 12 weeks were no less likely to develop respiratory infections than those given placebo pills.
Dr. Laaksi said larger clinical trials looking at different doses of vitamin D are still needed before the vitamin can be recommended for curbing the risk of respiratory infections.
SOURCE: http://link.reuters.com/dan53n
J Infect Dis 2010.
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