Adding just a little zinc to the diet can greatly reduce cases of malaria, diarrhea and pneumonia, researchers say.

They said zinc - touted in the United States in recent years as a way to soften the effects of the common cold - boosts the immune system and can save lives in developing countries."The incredible thing about zinc is that if you look at the three major killers of children everywhere - diarrhea, malaria and pneumonia - we are seeing that zinc has a very significant impact on reducing the severity and incidence of those," said Anuraj Shankar, an immunologist at the Johns Hopkins School of Public Health.

The August issue of the American Journal of Clinical Nutrition is devoted to studies on zinc and health. Shankar, working with other experts in a child health study, found the trace mineral can have remarkable effects.

They found that adding zinc to the diet - and only a little is needed - could reduce the duration of a diarrhea attack by 20 to 30 percent and could stop up to 38 percent of cases from ever happening at all.

It reduced acute respiratory infections such as pneumonia by up to 45 percent, Shankar said in a telephone interview.

"We are finding reductions in malaria of 35 percent or more," he added.

A study Shankar did in Peru found that when pregnant women were given zinc, their children were healthier for a year after birth.

"You're looking at a low-cost, effective way to promote maternal and child health. You're not going to cure every problem with this but you are going to significantly improve people's health," Shankar said.

He said researchers knew zinc was important, but it had taken a long time to figure out the potential impact.

"Only now, in the last five years really, have people been doing controlled trials with zinc," he said.

One study in India found that children with low blood levels of zinc had more bouts of diarrhea, and were more likely to have fever along with diarrhea.

A study in Vietnam found a 21/2-fold decrease in all respiratory infections when children got zinc.

Shankar, who studies the effects of nutrients on the immune system, said zinc is vital.