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Implication for practice and research
▪ Zinc supplementation as an adjunct therapy to oral rehydration solution (ORS) has been shown to reduce duration and severity of the diarrhoea episode among children <5 years of age in low- and middle-income countries.
▪ Zinc-fortified ORS should not take the place of zinc in addition to ORS in low- and middle-income countries.
▪ Additional research is needed before ‘super ORS’ should be recommended as a treatment in high-income countries which should include studies comparing efficacy and cost of zinc alone plus ORS with the combined zinc, ORS and prebiotic treatment.
Diarrhoea continues to be the second leading cause of death among children below 5 years of age around the world.1 Zinc-fortified ORS solution has been shown to be efficacious in decreasing stool frequency and proportion of episodes extending beyond 7 days when investigated in young Indian children.2 There is also evidence that zinc syrup alone is more efficacious than the zinc-fortified ORS.2 The treatment of diarrhoea is simple and inexpensive. ORS should be used for the prevention and treatment of dehydration, and zinc supplementation should be used to shorten the duration and severity and to decrease diarrhoea incidence in the 2–3 months following treatment.3
The authors randomised 119 Italian children, aged 3–36 months, with acute diarrhoea to receive ORS or ‘super ORS’ that was fortified with zinc and prebiotics. They did not include a group of children to receive the WHO-recommended treatment of ORS and zinc supplementation of 10 mg (0–5 months) and 20 mg (6–59 months), respectively.
The authors observed that a higher proportion of children recovered within 72 h among those receiving the ‘super ORS’ (72.9%) compared with those receiving standard ORS (50%, p=0.01). Children receiving the ‘super ORS’ also consumed more ORS in the first 24 h and reported the need for fewer additional medications to treat the episode.
Zinc supplementation in addition to ORS is being actively promoted in low- and middle-income countries around the world only as a supplemental, dispersible tablet or syrup and not as an ORS fortificant. Zinc-fortified ORS is not part of the WHO/Unicef recommendation, and it has not been widely studied after the initial study by Bahl and colleagues2 for a number of reasons. Although there are clinical guidelines suggesting the ideal quantity of ORS a child should consume to prevent and treat diarrhoea, the reality of how much ORS a child drinks per day during the course of an episode varies widely. For this reason, it becomes difficult to determine the correct dose of zinc to be added to the ORS. At any given amount, there will be children who are at risk of overdosing on one hand, and, perhaps far more likely, those who will consume too little and thus not receive the benefit of the zinc on the other.
Zinc is also recommended for 10–14 days, and ORS is typically consumed only until the dehydration is corrected. Giving zinc for a longer period, and not just as a quick treatment, has been shown to reduce the incidence and prevalence of diarrhoea and pneumonia in the 2–3 months following an episode.4 It is unlikely that this benefit would be observed in a cohort of children taking zinc for 1–3 days, which is the duration we would expect if zinc were only given with the ORS. It should be noted that, because zinc has not been widely studied in developed countries, we cannot be sure whether this preventive effect would be observed in these populations.
It would have been helpful if the authors had cited the Bahl et al study,2 the only study till date assessing the efficacy of zinc-fortified ORS, and addressed questions with regard to their choice of study design, which failed to compare zinc supplementation alone with zinc-fortified ORS – a main conclusion of the original Bahl et al study. There is little evidence demonstrating the effect of prebiotics as an adjunct treatment for infectious diarrhoea. As this study combines prebiotics and zinc, it is not possible to use these data to draw conclusions as to the individual benefit of prebiotics. The addition of prebiotics should be questioned until more conclusive data are available.
Zinc supplementation has been shown to decrease the duration and severity of diarrhoea when given in addition to ORS to children in low- and middle-income countries where it is suspected that children are at a far greater risk of zinc deficiency. The findings in this study are interesting, given that these results are consistent with what has been observed in developing countries though this study was conducted in Italy. Although there have been no studies of zinc supplementation for diarrhoea treatment among children in high-income countries, the study by Passariello and colleagues suggests that zinc may offer some benefit to these children as well.
Zinc is safe and, when given at the WHO-recommended dose of 10–20 mg/day, has no clinical side effects. These findings suggest the need for additional studies of zinc supplementation as an adjunct treatment for diarrhoea in addition to ORS and including them as a ‘super ORS’ among children in developed countries. Although diarrhoea mortality is low among children in developed countries, diarrhoea morbidity remains an economic and social burden resulting in expensive physician visits as well and time off from work and school.
Competing interests None.
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