Maternal supplemental and dietary zinc intake and the occurrence of neuraltube defects in California

The authors investigated the association between maternal preconceptional s upplemental and dietary zinc intake and risk of neural tube defects (NTDs) in a population-based case-control study conducted between 1989 and 1991 in California. Cases were 430 NTD-affected fetuses/infants, and controls were 429 randomly selected non-malformed infants. Mothers reported their precon ceptional use of vitamin, mineral, and food supplements, and completed a 98 -item food frequency questionnaire. Increased total preconceptional zinc in take was associated with a reduced risk for NTDs (quintiie 5 vs, quintile 1 , odds ratio (OR) = 0.65, 95% confidence interval (CI) 0.43, 0.99). Phytate intake, a constituent of the diet known to impede zinc absorption, appeare d to modify the zinc - NTD association. In addition, increased servings of animal products, the most bioavailable food source of zinc, was associated with a reduced risk for NTDs (quintile 5 vs. quintile 1, OR = 0.49, 95% CI 0.32, 0.76). Risk estimates for zinc intake were changed little after contr olling for multiple sociodemographic factors and total folate intake, but w ere attenuated after controlling for nutrients highly correlated with dieta ry sources of zinc, such as protein. In sum, the analyses indicate that ris k of NTDs in infants and fetuses decreased with increasing maternal preconc eptional zinc intake. However, it remains unclear whether increased zinc in take, or another nutrient or combination of nutrients highly correlated wit h zinc intake in the diet, is causally associated with reduced NTD risk.