Zinc supplements, a popular if controversial weapon against colds in the United States, are effective in treating cases of severe pneumonia, researchers reported yesterday.
In a study in Bangladesh, zinc added to a standard antibiotic helped hospitalized children recover faster. Perhaps more significantly, it prevented outright treatment failures - suggesting that doctors might not have to switch antibiotics as often to get results.
By reducing a child's exposure to antibiotics, doctors hope they will be able to stem the worrisome growth of antibiotic-resistant diseases, which are fast becoming a public health scourge worldwide.
With publication of the latest study, led by doctors at the Johns Hopkins Bloomberg School of Public Health, zinc looms as a potentially powerful tool against infectious diseases in the Third World.
Previous studies had shown that zinc is effective in preventing and treating diarrheal diseases, the second-leading killer of children worldwide. Research had also shown that the trace mineral prevents pneumonia, the No. 1 killer.
"It was beyond dispute that zinc helps to prevent pneumonia," said Dr. W. Abdullah Brooks, an infectious disease researcher at the Hopkins public health school and lead author of the study. "No one showed that it had a treatment benefit."
An estimated 2 million children die of pneumonia each year, and 1.7 million succumb to diarrheal disease.
The study appeared the same week that the World Health Organization and UNICEF jointly recommended zinc as part of an international strategy against diarrheal disease. The other key element is oral rehydration therapy, a mineral-rich solution that prevents dehydration.
Dr. Robert Black, director of international health at Hopkins, said zinc plays an important role in the immune system.
Children who have been subjects in diarrhea and pneumonia studies come from populations that are generally deficient in zinc, he said, and zinc therapy might have worked by correcting the deficiencies.
It is not clear whether giving zinc can help people who already get enough from their diets, Black said.
Scientists, including those taking part in the study, appear divided on whether zinc's only role is correcting a nutritional deficit. Admitting the issue is far from settled, Brooks said he believes that zinc might act more like a drug - boosting immunity by other means.
Zinc is present in many edible plants but exists in much higher concentrations in meat. In the United States, where zinc deficiency is rare, people get most of their zinc from poultry and red meat.
In Bangladesh, scientists studied 270 children under age 2 who were being treated for severe pneumonia. Also participating were researchers from the International Center for Diarrheal Disease Research in Bangladesh.
All the children in the study received antibiotics. Half also took zinc supplements, while half took a placebo.
Those receiving zinc recovered after an average of three days, compared with four in the placebo group. More impressively, according to Black, just two children taking zinc failed to get better with a single antibiotic regimen, compared with nine in the placebo group.
"This is really exciting because we think it really has the potential for improving the treatment of pneumonia," said Black, adding that zinc supplementation costs a penny a day.
Children in the study received 20 milligrams of zinc a day, almost seven times the recommended daily allowance for young children in the United States.
The study does not settle whether zinc is a cold fighter. In 2002, Americans spent $58 million on zinc lozenges and supplements, making it the fourth most popular dietary supplement, according to the Nutrition Business Journal.
Brian Sanderoff, a pharmacist who specializes in herbs and dietary supplements at his Owings Mills store, said he believes zinc deficiency is more common in the United States than is generally thought. To him, zinc's benefits are clear.
"I've had patients who used to get five or six colds a year and now don't get any," said Sanderoff, who also recommends zinc for prevention of enlarged prostate and many other conditions.
According to the National Institutes of Health, researchers have come to different conclusions about zinc's power against the common cold.