Vitamins and minerals

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Abstract

Taking vitamins and minerals to fight the common cold is popular in western countries and thus it is important to find out whether or not they are effective. A large number of trials have found that regular vitamin C supplementation shortens the duration of colds, and is probably beneficial when administered therapeutically starting soon after the onset of symptoms. Zinc lozenges have reduced the duration of common cold symptoms when the total daily zinc doses were over 70 mg. Consequently, both vitamin C and zinc have the potential to become options for treating the common cold, but more research is needed to determine optimal doses and treatment strategies. The prophylactic effect of vitamins and minerals has also been examined in several trials. Vitamin C has no preventive effect in the general community, but may reduce the incidence of respiratory symptoms in restricted population groups such as people under acute physical stress and people with a particularly low dietary intake of vitamin C. There is no evidence that vitamin E supplementation prevents colds in middle-aged people. Nevertheless, the effects of vitamin E in elderly males have been found to be heterogeneous, and further studies are warranted in elderly people. β-Carotene has been promoted for improving the immune system, but there is no evidence that it is effective against colds. The use of multivitamin and multimineral combinations against respiratory tract infections in elderly people has been studied in a number of trials, but a nearly uniform lack of efficacy has been found. Vitamin D and folic acid have been constituents of multivitamin supplements, and the absence of benefits of these supplements implies that increasing the intake of vitamin D or folic acid in elderly people would not have substantial preventive effects against respiratory infections.