Background. Low birth weight infants have been noted to have low zinc concentrations in cord blood, and zinc deficiency in childhood is associated with reduced immunocompetence and increased infectious disease morbidity. This study investigates whether zinc supplementation of infants born full term and small for gestational age affects mortality.
Methods. A randomized, double-blind, controlled trial with 2-by-2 factorial design enrolled 1154 full-term small for gestational age infants to receive in syrup 1 of the following: riboflavin; riboflavin and zinc (5 mg as sulfate); riboflavin, calcium, phosphorus, folate, and iron; or riboflavin, zinc, calcium, phosphorus, folate, and iron. A fixed dosage of 5 mL per child was given daily from 30 to 284 days of age. Household visits were made 6 days per week to provide the syrup and conduct surveillance for illness and death. When a child’s death was reported, parental reports and medical records were used to ascertain the cause. The effects of zinc and of the combination of iron, folate, calcium, and phosphorus were analyzed by intent to treat. The mortality analysis was performed using a survival analytic approach that models time until death as the dependent variable; all models had 2 terms as independent variables: 1 for the zinc effect and 1 for the vitamin and mineral (calcium and phosphorus, folate and iron) effect.
Results. Zinc supplementation was associated with significantly lower mortality, with a rate ratio of 0.32 (95% confidence interval: 0.12–0.89). Calcium, phosphorus, folate, and iron supplementation was not associated with a mortality reduction, although a statistically nonsignificant trend toward reduction was observed with a rate ratio of 0.88 (95% confidence interval: 0.36–2.15).
Conclusion. Zinc supplementation in small for gestational age infants can result in a substantial reduction in infectious disease mortality.