Zinc supplementation in Bangladeshi women and infants: effects on pregnancy outcome, infant growth, morbidity and immune response

Abstract

Zinc plays an essential role during periods of rapid growth and development, and is therefore important during the periods of gestation, fetal life, and early infancy. In this thesis two intervention studies are described to evaluate the effect of zinc supplementation during the last six months of pregnancy or between 1 and 6 months of age in infancy on pregnancy outcome, infant growth, morbidity from infectious diseases and immune response to childhood vaccines during the first six months of life. The study was performed in the urban slum areas of Dhaka, Bangladesh; an area where low birth weight (LBW) is prevalent and zinc deficiency is assumed to be common.The results showed that supplementation with 30 mg elemental zinc/day during the last two trimesters of pregnancy, did not improve intra-uterine or postnatal growth but resulted in a reduced morbidity from diarrheal diseases and impetigo in the infants during the first six months of life, particularly in infants born with LBW. These effects were most likely due to improved cellular immunity in these infants as indicated by a higher proportion of positive responses to the tuberculin skin test at 6 months of age. Supplementation of infants with 5 mg elemental zinc/day from 4 to 24 weeks of age improved linear and ponderal growth and reduced morbidity from Acute Lower Respiratory Infections (ALRI) but only in a small proportion of infants that were zinc deficient at 4 weeks of age. In most infants however, supplementation with zinc did not have any effect on growth or morbidity. There was no clear effect of zinc supplementation on infant's immune response. Zinc improved the antibody response to certain specific Pneumococcal serotypes whereas a very small but negative effect of zinc on the response to the tuberculin skin test was observed.In conclusion, the findings of this study suggest that child health and survival programs in less developed countries should consider the inclusion of zinc in antenatal multiple micronutrient supplements especially in regions where LBW is prevalent. More research is required to enable formulation of policy directions regarding the use of zinc supplements in infants during the first six months of life.</p