A new study finds little evidence that multivitamin and mineral supplements protect older people from infection.
The authors of the study reviewed the results of eight randomized, controlled trials that examined the effect of multivitamin and mineral supplements on infections in elderly people.
Three of the studies found multivitamins reduced the average number of days spent with infection each year by 17.5.
Overall, however, the authors say that evidence for the effectiveness of multivitamin and mineral supplements was "conflicting."
The conflicting results may have been due to several factors: the use of supplements that had different compositions, participants who started out with varying nutritional statuses and differences in follow-up times and seasonal periods covered.
There was also little evidence of adverse effects from taking vitamin supplements, but the authors say this may have stemmed from poor reporting.
The studies seemed to raise more questions than answers, according to the British researchers.
Experts still do not know how multivitamin and mineral supplements work-if, in fact, they do. The researchers speculate that the nutrients in these supplements may have an effect on immunity or correct an underlying deficiency.
"Everyone wants to take a vitamin because they're always worried that they are deficient, and in the olden days, they might have been," says Dr. Tharakaram Ravishankar, medical director of Glen Cove Center for Nursing and Rehabilitation in Glen Cove, New York. "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."
"People think that 'If I take a multivitamin, I won't get sick," Ravishankar says. "It won't prevent infection, especially if you have a diabetes or another condition where the immune system is compromised." Supplements are not going to prevent a cold or cough, he adds.
However, the results of the trials studied were "sufficiently encouraging" to warrant more study, the British team concludes. Randomized controlled trials would provide insight into whether doctors should recommend the routine use of these products, they say.