THURSDAY, March 31, 2005 (HealthDay News) -- A new study finds little evidence that multivitamin and mineral supplements protect against infections in older people.
More randomized controlled trials need to be done before doctors can recommend routine use of these products, concluded researchers in a report posted Thursday in the online edition of the British Medical Journal.
"Everyone wants to take a vitamin because they're always worried that they are deficient and, in the olden days, they might have been," said Dr. Tharakaram Ravishankar, medical director of Glen Cove Center for Nursing and Rehabilitation in Glen Cove, N.Y. "But now a lot of supplements are in food so, actually, you really won't be having any vitamin deficiency if you're eating proper meals." Ravishankar was not involved in the study, which was conducted by researchers at Royal Hallamshire Hospital, Sheffield, and the University of Leicester, both in England.
According to the study authors, the elderly are the fastest growing segment of the population in the developed world. And as people age, their chance of acquiring an infection increases. Older people are up to 10 times more likely to die of infection than younger adults, the researchers said.
In light of these facts, there's been growing interest -- and a growing market -- in vitamin supplements aimed at reducing the risk of infection. According to the study, 20 to 30 percent of people in developed countries already use these supplements, despite a lack of scientific evidence supporting their use.
The authors of the study reviewed completed, randomized, controlled trials that examined the effect of multivitamins and mineral supplements on infections in elderly people. In all, they identified only eight trials that fit their criteria.
Three of the studies did find that multivitamins reduced the average number of days spent with infection each year by 17.5.
Overall, however, the authors stated, evidence for the effectiveness of multivitamins and mineral supplements was "of poor to moderate quality, heterogeneous and conflicting."
The differences in study quality and results may have been due to the use of supplements with different compositions, the recruiting of participants who started out with varying nutritional status and differences in study follow-up times and seasonal periods covered. Any or all of these factors may have accounted for the differences seen in the results, the researchers said.
There was also little evidence of adverse effects from consuming vitamin supplements, but the authors noted that this may have stemmed from poor reporting. Other studies, in which individuals used larger doses of micronutrient supplements, did show some toxic effects, but these studies were not included in the meta-analysis.
Overall, the studies seemed to raise more questions than they answered, according to the British researchers. They noted that when the authors of six of the earlier trials were contacted, none responded.
An additional problem is that experts still do not know how multivitamins and mineral supplements might work -- if, in fact, they do work at all. The mechanism could be related to the nutrients' effects on immunity, an improvement of an underlying deficiency or something else entirely.
Still, the results of the trials studied were "sufficiently encouraging" to warrant more study, the British team concluded.
Specific supplements might have some benefit, Ravishankar noted. "Folic acid seems to help in cardiovascular disease, especially in women," he said.
Vitamin E, on the other hand, does not seem to have any benefit. And, while antioxidants taken at a younger age may help with vascular damage, that doesn't mean they have any effect on preventing infection.
"People think that if I take a multivitamin, I won't get sick," Ravishankar said. "It won't prevent against infection, especially if you have diabetes or another condition where the immune system is compromised. That's not going to make you not get a cold or cough."
More information
The U.S. Department of Agriculture has more on vitamins and minerals.
