Zinc supplementation can be ineffective in the treatment of diarrhea. A randomised controlled trial published in the open access journal BMC Medicine has shown that supplementation with either zinc or zinc and copper is no more effective than placebo.
Archana Patel, from the Lata Medical Research Foundation, India, led a team of researchers who studied the effects of the different supplements on a group of 808 children in Nagpur, also in India. She said, "The expected beneficial effects of zinc supplementation for acute diarrhea were not observed. Therapeutic zinc or zinc and copper supplementation may not have a universal beneficial impact on the duration of acute diarrhea in children".
The authors found that neither duration of diarrhoea, total stool weight, use of oral rehydration salts nor use of intravenous fluids were affected by supplementation. The authors said, "There could be many reasons for the lack of effect observed in our study. Although our study controlled for baseline serum zinc concentrations, these are not always a reliable measure of body zinc status. As such, baseline zinc deficiency in our subjects may have affected our results. Different diarrhea etiologies and the impact of interactions of zinc with multi-vitamins shown in previous studies may also explain the difference between our study and others that have shown a positive effect."
The authors have called for a re-examination of all available trial data, including this one, to dissect out the potential contributors to heterogeneity of results before zinc can be universally recommended for treatment of acute childhood diarrhea.