Zinc supplementation shortens the duration of diarrhea in children (11.5 hours shorter duration), especially those who are malnourished (26 hours shorter).
Photo Credits: Shehzad Noorani
Why is zinc important?
Zinc is important for immune function and our ability to fight infections, particularly pneumonia and diarrhea. Zinc deficiency is common among children from low-income countries. Zinc is not stored in our bodies so it must be available in our daily diet or from supplements. Zinc can be used as a treatment for diarrhea.
Does zinc supplementation work?
- Zinc is effective for treating diarrhea.
Equity: does zinc supplementation work in the disadvantaged?
- Zinc was more effective in treating diarrhea malnourished children and reduced the duration of diarrhea by more than one day (about 26 hours). Zinc requirements are higher in malnourished children because zinc deficiencies are considered more severe for them.
- Most of the included studies administered zinc as a syrup however a few used tables or powders. The type of zinc used was zinc sulphate, zinc acetate, or zinc gluconate.
- Zinc was given once a day in most of the trials. In others it was given two or three times a day and one study gave a single dose.
- The dose of zinc ranged from 20-45 mg/day except one trial which provided 10 mg/day to children younger than 6 months and another that used 5 mg/day for children under 6 months. Three trials used a per kilogram dose (2-3mg/kg/day).
- Duration of supplementation varies and studies provided zinc for 1-2 weeks, until recovery, or until 7 days after recovery and one trial gave a single dose.
Population and Setting
- 33 studies were included in this review. The trials were conducted in hospitals or community settings and were conducted mostly in countries rated as high risk for zinc deficiency with some conducted in those at medium or rare risk.
Summary of Findings [SOF] Tables: Zinc compared to placebo for children older than 6 months with diarrhea
Patient or population: Children with acute diarrhea
Settings: all countries
Anticipated absolute effects per year
No of Participants
Quality of the evidence
Risk without zinc supplementation (Control)
Risk with zinc supplementation (95% CI)
Duration of diarrhea – all trials
Mean duration of diarrhea ranged from 31-170 hours
Duration of diarrhea was 11.5 hours shorter with zinc (from 3.2 to 19.7 hours shorter)
Duration of diarrhea – children with moderate malnutrition
Mean duration of diarrhea ranged from 103-147 hours
Duration of diarrhea was 26.4 hours shorter with zinc (from 16.2 to 36.5 hours shorter)
Diarrhea on the 7th day
128 per 1000
35 fewer (from 10-50 fewer)
RR 0.73 (0.61-0.88)
Adverse events (vomiting)
119 per 1000
69 more (from 54-123 more)
RR 1.57 (1.32-1.86)
Adverse Events: Vomiting was more common in the group receiving zinc supplementation than controls. The authors state that this is related to the metallic taste.
1. Downgraded by 1 for indirectness: all trials were conducted in Asia.
2. Downgraded by 1 for serious imprecision: wide CI.
3. Downgraded by 1 for serious indirectness: these trials were all conducted in Asia in countries at high risk of zinc deficiency
4. Downgraded by 1 for serious risk of bias: two trials reported no details on sequence generation, allocation concealment, blinding, and incomplete outcome data, while one did not give any details regarding allocation concealment.
Relevance of the review for disadvantaged communities
Equity - Which of the PROGRESS groups examined
Almost all of the included studies were conducted in low or middle income countries but the review did not report on socioeconomic status of participants. One study was conducted in a high income country. Most of the countries were ranked as high risk for zinc deficiency.
In areas where zinc deficiency are high, zinc is an effective treatment for diarrhea.
Eight of the included studies only enrolled malnourished children, two only enrolled well-nourished children, one enrolled all children regardless of nutritional status, and 20 trials enrolled well nourished children or those with mild or moderate malnutrition. None of the included studies enrolled children with severe malnutrition. Six studies were conducted in community-settings, one was conducted in both community and hospital settings and all the rest were conducted in hospitals.
Zinc supplementation is effective to reduce the duration of diarrhea for children, especially those who are zinc-deficient or mildly or moderately malnourished. Future studies should examine the effect of zinc on children with severe malnutrition.
The dose of zinc ranged from 20-45 mg/day except one trial which provided 10 mg/day to children younger than 6 months and another that used 5 mg/day for children under 6 months. Three trials used a per kilogram dose (2-3mg/kg/day).
The type of zinc used in 8 trials was zinc acetate and 5 used zinc gluconate. Three did not specify. The rest used zinc sulfate.
Most trials administered zinc as a syrup but 4 used powder, 7 used tablets, 2 mixed zinc with oral rehydration solution, and one did not specify.
Zinc was given daily in most of the trials, twice daily in 5 trials, three times daily in 6 trials, and together with oral rehydration solution depending on stool frequency in 2 trials. One trial gave zinc twice a day to infants and a single dose to children over 6 months old.
Since zinc is not stored in the body, adequate zinc must be made available daily. Policy makers and practitioners will need to consider their local setting to determine the most suitable delivery mechanism and schedule. The supplements must be active and stored properly.
The review did not report on the cost-effectiveness of zinc for treating diarrhea overall or in each disadvantaged group.
The cost of zinc will vary based on local conditions. The included studies provided zinc short term for treating diarrhea. Policymakers will need to consider the cost effectiveness of zinc compared to other diarrhea treatments.
Comments on this summary? Please contact Jennifer Petkovic.