Several epidemiological studies have found associations between asthma and lowered intake (and blood levels) of antioxidant vitamins including C, E, and β-carotene as well as trace elements such as zinc. Supplementation has not, however, consistently lessened the risk of asthma-related outcomes. The authors previously reported an increased risk of wheezing at age 2 years when maternal vitamin E intake was reduced during pregnancy. The present longitudinal cohort study enrolled 1861 children whose mothers were recruited during pregnancy and who have been followed up to age 5 years. Both a food frequency questionnaire and plasma levels were used to assess maternal nutritional status. Asthma status was assessed by skin-prick testing in 700 children, estimates of 1-second forced expiratory volume (FEV1) in 478, and measurements of exhaled nitric oxide in 167.
No consistent associations were found between wheezing, asthma, eczema, or atopic sensitization at age 5 years and the maternal intake of vitamin C or β-carotene, but maternal vitamin E intake during pregnancy, determined at 32 weeks’ gestation, correlated negatively with wheezing and asthma in the children. Maternal plasma levels of α-tocopherol during pregnancy correlated positively with postbronchodilator values of FEV1. Maternal intake of zinc during pregnancy correlated negatively with both active asthma and having asthma at any time. The association between maternal vitamin E intake during pregnancy and the child’s intake at age 5 was very weak, and no consistent associations were found between respiratory outcomes and children’s intake of vitamin E, vitamin C, or zinc at age 5.
These findings warrant further studies to determine whether dietary change or the provision of supplements during pregnancy can lower the risk of asthma and related outcomes in young children. It also remains unclear whether any associations between maternal nutritional status and adverse respiratory outcomes persist in later childhood.