Zinc supplementation has been shown to improve diarrhea and pneumonia in children from regions where zinc is deficient in the diet.  However, the effectiveness of preventive zinc supplementation for health improvement and child growth is not well documented.  Islam and colleagues conducted a study to explore the impact of dose, duration, and frequency of zinc supplementation on the incidence of diarrhea and linear growth in children.  They report their results in the May 2022 issue of The Journal of Nutrition.

Children (9-11 months, n=2886) were enrolled in a randomized, partially double-blind, controlled, 6-arm, community-based efficacy trial.  They were assigned to receive one of the following interventions over a 24 week period: 1) micronutrient powder (MNP, 4.1 mg zinc and 10 mg iron) daily; 2) high-zinc (10 mg), low-iron (6 mg) MNP daily; 3) high zinc (10 mg) and low iron (6 mg) or a no-iron MNP on alternating days; 4) dispersible zinc tablet (10 mg); 5) dispersible zinc table (10 mg) for 2 weeks at enrollment and at 12 weeks; or 6) placebo powder.  Incidence of diarrhea and change in length-for-age Z score over the 24 week period were determined.

There were no differences in the incidence or prevalence of diarrhea among any of the treatment groups.  A smaller decline in length-for-age Z score was observed in those receiving the high zinc and low iron MNP, as compared with the placebo powder group.  The authors concluded that the dose, duration, and frequency of zinc in the MNPs used in the study were unable to reduce diarrhea, even though the high zinc and low iron MNP provided modest improvements in the length-for-age Z scores of the children.

In an editorial, Wieringa states the lack of effect in this study is similar to previous results that failed to show improvement in linear growth with MNP supplements, probably because diets are lacking protein, energy, essential fatty acids, in addition to micronutrients.  Wieringa suggests that although providing a complete and diverse diet is the preferred way to resolve deficiencies, fortified supplements such as complementary foods with high nutrient density or supplementary lipid-based foods should be used to improve nutrient status of children.  Wieringa concludes that preventive zinc supplements do not appear to be an effective approach.


M Munirul Islam, Robert E Black, Nancy F Krebs, Jamie Westcott, Julie Long, Kazi Munisul Islam, Janet M Peerson, Rahvia Alam Sthity, Afsana Mim Khandaker, Mehedi Hasan, Shams El Arifeen, Tahmeed Ahmed, Janet C King, Christine M McDonald, Different Doses, Forms, and Frequencies of Zinc Supplementation for the Prevention of Diarrhea and Promotion of Linear Growth among Young Bangladeshi Children: A Six-Arm, Randomized, Community-Based Efficacy Trial, The Journal of Nutrition, Volume 152, Issue 5, May 2022, Pages 1306–1315, https://doi.org/10.1093/jn/nxab439.

Frank T Wieringa, Has Zinc Lost Its Shine?, The Journal of Nutrition, Volume 152, Issue 5, May 2022, Pages 1185–1186, https://doi.org/10.1093/jn/nxac028.

Images via canva.com.