Background/Aims: Zinc intake and serum zinc concentrations are lower in adult vegetarians compared to omnivores. The additional zinc demands associated with pregnancy and foetal development may dispose pregnant vegetarians to increased risk of zinc deficiency. The present systematic review and meta-analysis compares the zinc intake and status of vegetarian and omnivorous women during pregnancy. The association between vegetarian diets and functional pregnancy outcomes also is considered.
Methods: A literature search was conducted of MEDLINE; PubMed; Embase; the Cochrane Library; Web of Science; and Scopus electronic databases up to September 2014. Six observational studies published in English that examined zinc intake and/or status in vegetarian compared to non-vegetarian pregnant women qualified for inclusion in the systematic review.
Results: In a meta-analysis of dietary zinc intake, vegetarians were found to have lower zinc intakes than non-vegetarians (−1.38 ± 0.35 mg/day; p < 0.001). Neither the vegetarian nor non-vegetarian group met the recommended dietary allowance for zinc. In a qualitative synthesis, no differences were found between groups in serum zinc or in functional outcomes associated with pregnancy.
Conclusions: Pregnant vegetarians have lower zinc intakes than non-vegetarian control groups, however there is no evidence that this disparity results in adverse effects to the mother or foetus. Further information is needed to determine whether physiologic adaptations in zinc metabolism are sufficient to meet the requirements of pregnancy on a low zinc diet. Meanwhile, dietary advice that increases the zinc intake of both vegetarian and omnivorous pregnant populations to recommended levels is prudent.