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Supplementing iron and zinc: double blind, randomized evaluation of separate or combined delivery



Many children have diets deficient in both iron and zinc, but there has been some evidence of negative interactions when they are supplemented together. The optimal delivery approach would maximize clinical benefits of both nutrients. We studied the effectiveness of different iron and zinc supplement delivery approaches to improve diarrhea and anemia in a rural Bangladesh population.

Study Design:

Randomized, double blind, placebo-controlled factorial community trial.


Iron supplementation alone increased diarrhea, but adding zinc, separately or together, attenuated these harmful effects. Combined zinc and iron was as effective as iron alone for iron outcomes. All supplements were vomited <1% of the time, but combined iron and zinc were vomited significantly more than any of the other supplements. Children receiving zinc and iron (together or separately) had fewer hospitalizations. Separating delivery of iron and zinc may have some additional benefit in stunted children.


Separate and combined administration of iron and zinc are equally effective for reducing diarrhea, hospitalizations and improving iron outcomes. There may be some benefit in separate administration in stunted children.

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This study was funded by the US Agency for International Development through the Global Research Activity award #HRN-A-00-96-90006-00 to the Johns Hopkins Bloomberg School of Public Health. We thank Saifuddin Ahmed (Johns Hopkins Bloomberg School of Public Health) and Parivash Nourjah (Johns Hopkins Medical Institutions, Agency for Healthcare Research and Quality) for their statistical assistance, Hervé-Pierre Le Goascoz (Nutriset) and Neal Brandes (USAID) for their assistance and support through this project, and most of all the entire ICDDR,B team, the Kumudini hospital staff, and the Mirzapur community.

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Correspondence to S Chang.

Additional information

Contributors: SC, AB, RB, SA, MW, KZ contributed to study design. SA, SB, MW, KMR, TR, AM, NB contributed to collection of data. SC, RB contributed to analysis of data. SC prepared the first draft of the manuscript. All authors provided significant advice, contributed to, and approved the final manuscript.This study was registered in (identifier number NCT00470158), and approved by the Johns Hopkins Bloomberg School of Public Health Institutional Review Board (H. and the International Centre for Diarrhoeal Disease Research, Bangladesh Ethical Review Committee (2005-040).


The findings and conclusions in this document are those of the authors, who are responsible for its contents; the findings and conclusions do not necessarily represent the views of AHRQ or USAID. Therefore, no statement in this report should be construed as an official position of these entities, the US Department of Health and Human Services, or the US Agency for International Development.

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Chang, S., El Arifeen, S., Bari, S. et al. Supplementing iron and zinc: double blind, randomized evaluation of separate or combined delivery. Eur J Clin Nutr 64, 153–160 (2010).

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  • iron
  • zinc
  • supplement
  • delivery
  • interaction
  • diarrhea

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