News
Zinc supplementation prevents diarrhoea and pneumonia 
Gavin Yamey , BMJ 

Dietary zinc supplementation reduces the incidence of childhood pneumonia by 
41%and the prevalence of diarrhoea by up to 25%according to a systematic 
review of 10 randomised controlled trials all performed in the developing 
world (Journal of Pediatrics 1999;135:689-97). 

This compares favourably with other preventive interventions for diarrhoea, 
such as sanitation and breast feeding, and is more effective than any other 
intervention to prevent pneumonia. 

Zinc deficiency is common in young children in the developing world and is 
associated with reduced immunocompetence and increased rates of serious 
infectious diseases. Several trials in poor countries have shown the benefit 
of zinc supplementation in reducing infection (BMJ 1998;317:369), but these 
have varied in the magnitude of the effect and the presence of a differential 
effect by age and sex. Some trials were underpowered to detect the effects on 
infrequent outcomes, and others remain unpublished. 

A pooled analysis was conducted by the Child Health Research Project, a group 
of researchers from Johns Hopkins School of Public Health and the World 
Health Organisation, who had access to the original trial data. Trials were 
included if they provided oral supplements containing at least half the US 
recommended daily allowance of zinc for children, and if morbidity 
surveillance was carried out for at least four weeks. Two sets of trials were 
identifiedthose in which zinc was given continuously, and those giving only a 
short course. 

For the zinc supplemented children in the seven continuous trials, the pooled 
odds ratios for diarrhoeal incidence and prevalence were 0.82 (95%CI 0.72 to 
0.93) and 0.75 (0.63 to 0.88) respectively. Supplemented children had an odds 
ratio of 0.59 (0.41 to 0.83) for incidence of pneumonia. 

No significant variations in the effects were seen in the subgroups of 
children stratified by age, sex, and weight, and nor was there a significant 
difference between short course and long term supplementation. 

The authors conclude that "the development of effective and feasible 
interventions to improve the zinc status of developing country populations is 
essential." One such intervention, zinc fortification of bread, was shown in 
a randomised controlled trial to reduce diarrhoea, respiratory illnesses, and 
skin infections in Turkish schoolchildren (Cereal Chemistry 1995;73:424-6). 

Dr Robert Black, of Johns Hopkins School of Public Health and co-author of 
the study, said: "Zinc fortification is potentially a powerful tool for 
settings which produce commercial food, and the idea has been acceptable to 
food manufacturers. If there's no commercial food, increasing zinc intake is 
possible by reducing the amount of dietary phytates, which interfere with 
zinc absorption. This can be done by soaking or fermenting food. Long term, 
it is possible that plant breeding could be used to increase zinc or reduce 
phytate content." 

But several questions still remain before zinc therapy can be incorporated 
into diarrhoeal disease control programmes, including the optimal dosing 
regime and duration of therapy. Dr Shammim Qazi, from the Division of Child 
Health and Development of the World Health Organisation, said: "At present 
the WHO is not recommending zinc supplementation as routine. We are waiting 
for the results of larger trials, and we are planning a trial ourselves." 

The Child Health Research Project's Special Report, Zinc for Child Health, is 
at http://ih.jhsph.edu/chr/publicat.htm 
© British Medical Journal 1999