Zinc supplementation: effects on the growth and morbidity of undernourished Jamaican children

We investigated whether there was a growth or morbidity response to zinc supplementation. The study was randomized, placebo-controlled, and double-blind. Children were recruited at clinics in Kingston, Jamaica, and supplemented at home. Children selected were singletons aged 6-24 months, and stunted (< -2.0 s.d. length for age, NCHS references). They were stratified by sex and age and randomly assigned to receive zinc supplement (n = 31) or placebo (n = 30). Four children were excluded because of hospitalization; all others had all measurements. Adequately nourished children (n = 24) were recruited from a well-baby clinic. The supplement provided 5 mg elemental zinc in a syrup daily for 12 weeks; the placebo comprised the syrup only. Caretakers were interviewed to obtain social background data, number of clinic visits and hospitalizations. Anthropometric measurements were done on enrolment, and after 6 weeks, 12 weeks and 12 months. Children's health was determined by weekly questionnaire to caretakers of the undernourished groups during the supplementation period. The supplemented and placebo groups were similar on enrolment. The adequately nourished children were from significantly better socio-economic circumstances. Mean initial hair zinc content was 5.5 +/- 4.8 mumol/g (supplemented group) and 6.7 +/- 12.1 mumol/g (placebo)(n.s.). Regression analyses showed that there were no significant effects of supplementation on length, height or head circumference, nor on the incidence of any morbidity symptom. Mean duration of the episodes was significantly shorter for skin rashes in the supplemented group compared with the control group (ANCOVA, P = 0.02), and longer for vomiting (P = 0.02). The incidence of hospitalization was significantly greater in the control group (Fisher's exact test, P = 0.02). Zinc supplementation reduced the hospitalizations which probably reflect severity of morbidity, but did not improve growth.