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Zinc Supplements Help Undersized Infants Survive

Study seen as beneficial for developing countries

MONDAY, Dec. 3, 2001 (HealthDayNews) -- Babies with low birth weight are likelier to survive the first nine months of life if they're given zinc supplements, a new study says.

The supplements, given to undersized infants in India, were particularly helpful in preventing deaths from diarrhea, according to the study, which appears in the December issue of Pediatrics.

"We have done studies documenting morbidity effects, but this is the first trial documenting the mortality question," says Dr. Sunil Sazawal, lead author of the study and an associate scientist in international health at Johns Hopkins Bloomberg School of Public Health in Baltimore.

Sazawal cites previous research that found zinc supplements given to preschool children in developing countries reduced the incidence of pneumonia overall by 41 percent and the incidence of diarrhea overall by 18 percent.

According to the study, 20 million low birth-weight babies are born around the world every year, 90 percent of them in developing countries. These small infants are particularly vulnerable to diarrhea and respiratory infections, which are the primary causes of death in children under the age of 5.

Because low birth-weight babies have been shown to have low zinc concentrations in their cord blood and because zinc deficiency has been linked to depressed immunity, the authors set out to test whether adding zinc could increase the infants' odds of survival.

Between April 1996 and November 1998, the researchers looked at 1,154 full-term infants in New Delhi who were small for gestational age, meaning that their birth weight was less than the 10th percentile for that age. The babies were randomly assigned to one of four groups and, starting at the age of 30 days, were given one of the following combinations: riboflavin; riboflavin and zinc; riboflavin, calcium, phosphorus, folate and iron; or riboflavin, zinc, calcium, phosphorus, folate and iron.

The babies in the two groups that received zinc did indeed demonstrate a higher survival rate. Of the 20 documented deaths, only five infants had been given zinc. The results were most dramatic among the deaths caused by diarrhea: Only one infant had been given zinc, while nine had not.

There are a few caveats to these findings, however. Although he does not dispute the link between zinc supplements and reduced mortality, Dr. David Horwitz, a clinical associate professor of pediatrics at New York University Medical Center, does not feel the study fully establishes a link between added zinc and the immune system.

"I think the study is way too small to say this is an immune modulator as opposed to a better treatment for diarrhea," Horwitz says. "There are way too many other factors to say that for sure."

Also, just because added zinc is good for underweight children does not necessarily mean it's good for everyone, he adds. "You cannot extrapolate that zinc supplementation in healthy babies makes you better or is even good for you," he warns.

The findings appear far more significant for developing countries than for developed regions of the world, like the United States.

"It's not going to change anything dramatically in this country because we already supplement our babies who are small with extra zinc," says Dr. Asha Puri, interim director of neonatology at Cedars-Sinai Medical Center in Los Angeles. "Babies who are breast-fed are then supplemented with human milk fortifier, which has extra zinc to meet daily requirements."

But even for areas of the world where malnutrition and poverty are common, Puri feels several questions are unanswered.

"They had a big group of mothers who exclusively breast-fed, and mortality in that subset was low compared to the babies who were partially breast-fed," she says. "So the question is not so much zinc supplementation, but should we be doing something to teach these mothers how to sterilize the bottles better so the babies don't get infected?"

"This is a stepping-stone study. It doesn't prove anything, but it gives some direction for future work," Horwitz adds.

In fact, Sazawal and his colleagues are launching a trial with 50,000 children to see whether the benefits of zinc supplementation extend to children of normal weight. That study will take about two years to complete.

What To Do

For information on all aspects of baby and child health, visit the American Academy of Pediatrics.

For specific information on newborns, try Neonatology on the Web.

SOURCES: Interviews with Sunil Sazawal, M.D., Ph.D., associate scientist, department of international health, Johns Hopkins Bloomberg School of Public Health, Baltimore; Asha Puri, M.D., interim director of neonatology, Cedars-Sinai Medical Center, Los Angeles, and professor of pediatrics, University of California, Los Angeles; David Horwitz, M.D., clinical associate professor of pediatrics, New York University Medical Center, New York; December 2001 Pediatrics
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