Maternal hematologic status at delivery can be negatively affected by prenatal zinc and vitamin A supplements

The demand for zinc, vitamin A, iron, and other micronutrients increases during pregnancy. Deficiencies in these nutrients lead to poor pregnancy/birth outcomes, as well as anemia and infections. However, based on potential adverse interactions and similar absorption and transport mechanisms, there are some concerns about co-supplementation with zinc, vitamin A, and iron. Noor and colleagues addressed this question in a study published in the February 2020 issue of The Journal of Nutrition.

Data for the study were derived from two large randomized controlled trials conducted in Tanzania. Subjects from one study were provided daily zinc (25 mg) and/or vitamin A (2500 IU) from the first trimester through delivery and their results were compared to those receiving a placebo. Iron-replete subjects in the other study were provided iron (60 mg/day) to evaluate the safety and efficacy of the supplement. Baseline blood samples were analyzed, as were those collected at delivery, for hemoglobin, serum ferritin, soluble transferrin receptor, plasma zinc and zinc protoporphyrin.

Supplementation with zinc and vitamin A lowered hemoglobin concentrations at delivery, and vitamin A increased ferritin concentrations at delivery but led to increased risk of severe anemia. Iron supplementation reduced the risk of iron depletion at delivery. Zinc and iron supplements did not affect plasma zinc concentrations in either study. The data from these studies led the authors to conclude that supplementing zinc and vitamin A had no benefit to maternal hematologic status, but that iron supplementation was beneficial, even among iron replete individuals. They further concluded that more consideration should be given to the efficacy and safety of vitamin A supplement use.

Reference Noor RA, Abioye AI, Darling AM, Hertzmark E, Aboud S, Premji Z, Mugusi FM, Duggan C, Sudfeld CR, Spiegelman D, Fawzi W. Prenatal zinc and vitamin A reduce the benefit of iron on maternal hematologic and micronutrient status at delivery in Tanzania.The Journal of  Nutrition, DOI:  https://doi.org/10.1093/jn/nxz242. 

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Nancy Turner, PhD

Nancy Turner is a Professor of Nutrition at Michigan State University.  Her research focus is on the role of diet on colon cancer and inflammatory bowel disease.  She is the author of many papers on this topic, as well as the co-editor of a book, and co-author of a textbook.