NEW YORK (Reuters Health) - Treatment with zinc supplements can cut the severity and duration of acute or persistent diarrhoea in children, a study shows.

Further research, however, is needed to determine exactly how zinc produces its anti-diarrheal effects, the researchers note in the in the February issue of Pediatrics.

The findings stem from a pooled analysis of data from 22 relevant studies, including 16 that focused on the benefits of zinc in 15,231 children with acute diarrhea and six that looked at 2968 children with persistent diarrhoea.

Zinc use cut the average duration of both acute and persistent diarrhea, Dr. Marek Lukacik, from the Medical College of Georgia in Augusta, and colleagues report. In addition, zinc therapy reduced the average stool frequency by 18.8 percent and 12.5 percent in children with acute and persistent diarrhoea, respectively.

Zinc supplements also helped prevent diarrhea. Treatment with zinc supplements reduced the occurrence of both types of diarrhoea by roughly 18 percent relative to placebo.

On the downside, in most of the studies, zinc was more likely than placebo to cause vomiting.

"On the basis of these findings, which now add to the large body of previously published clinical data and update previous meta-analyses and systematic reviews, zinc therapy is useful for treating both acute and persistent diarrhoea and for their prophylaxis," the researchers conclude.

Diarrhea kills more than two million people each year, the World Health Organization estimates. Most are young children living in middle- or low-income countries.