Researchers have long known that zinc plays an important role in human health. Now, a new study shows that daily zinc supplements can protect Third World children from disease to a dramatic extent.

Zinc is one of the most plentiful substances in the body, second only to iron. It is vital to many bodily functions, including maintaining a healthy immune system. The study, conducted by researchers at the Johns Hopkins Bloomberg School of Public Health, examined whether zinc supplementation would help children who live in areas where malaria is common. Along with pneumonia and diarrhea, malaria accounts for 45 percent of the 10 million child deaths worldwide each year.

Researchers examined 42,546 children living in Pemba, Zanzibar. Half of the children were randomly selected to receive daily zinc supplements, while the other half were given a placebo.

Overall, the study found 18 percent fewer deaths in children aged 12 to 48 months, who were given the extra zinc. However, the researchers did not find any significant reduction among children 1 to 11 months of age. The study is published in the March 17, 2007, edition of The Lancet.

"This large trial demonstrates that the benefits of zinc supplementation include mortality reduction in addition to the reduction in cases of pneumonia, diarrhea and malaria that we found in previous trials," said Robert Black, M.D., the study's co-author and chair of the Bloomberg School's Department of International Health.

Why would zinc not help younger children? The researchers say that it is possible that infants acquire sufficient amounts of zinc before birth and through breast feeding to sustain them during the first year of life. The failure to find an effect in infants could also be a result of the lower doses of zinc given to infants.

"While further work is needed to evaluate higher dose effects, recommendations for use of zinc as a preventive strategy needs to consider the collective evidence of the effect on growth, morbidity and mortality, which would suggest benefit in children age 6 months and up," said co-author, Sunil Sazawal, Ph.D., associate professor in the Department of International Health.