Abstract
Pregnant women are vulnerable to a low zinc status due to the additional zinc demands associated with pregnancy and foetal development. The present systematic review explores the relationship between habitual vegetarian diets and dietary zinc intake/status during pregnancy. The association between vegetarian diets and functional pregnancy outcome also is considered. A literature search was conducted of MEDLINE; PubMed; Embase; the Cochrane Library; Web of Science; and Scopus electronic databases up to September 2014. Six English-language observational studies qualified for inclusion in the systematic review. A meta-analysis was conducted that compared the dietary zinc intake of pregnant vegetarian and non-vegetarian (NV) groups; the zinc intake of vegetarians was found to be lower than that of NV (−1.38 ± 0.35 mg/day; p < 0.001); and the exclusion of low meat eaters from the analysis revealed a greater difference (−1.53 ± 0.44 mg/day; p = 0.001). Neither vegetarian nor NV groups met the recommended dietary allowance (RDA) for zinc. In a qualitative synthesis; no differences were found between groups in serum/plasma zinc or in functional outcomes associated with pregnancy. In conclusion; pregnant vegetarian women have lower zinc intakes than NV control populations and both groups consume lower than recommended amounts. Further information is needed to determine whether physiologic adaptations in zinc metabolism are sufficient to meet maternal and foetal requirements during pregnancy on a low zinc diet.
Highlights
The involvement of zinc in numerous biological processes, including enzyme action, regulation of gene expression, and cell signalling, underscores the importance of this essential trace element in health [1,2]
Pregnant women are vulnerable to a low zinc status due to the additional zinc demands associated with pregnancy and foetal growth and development, with late pregnancy being the period of greatest need [8]
The balance of evidence evaluated in the present systematic review suggests that there is no difference between groups in biomarkers of zinc status or in functional outcomes associated with pregnancy
Summary
The involvement of zinc in numerous biological processes, including enzyme action, regulation of gene expression, and cell signalling, underscores the importance of this essential trace element in health [1,2]. Zinc is widely distributed in foods, with meat, fish, shellfish, and poultry being the major contributors of bioavailable zinc in the adult omnivorous diet [4]. Zinc is less bioavailable and likely to be present in lower amounts when obtained from plant-derived compared to animal food sources [5], suggesting that careful planning is required to ensure adequate amounts of absorbable zinc are present in a vegetarian diet. In a recent meta-analysis [6], dietary zinc intakes were found to be lower in adults who follow habitual vegetarian diets compared to omnivorous control groups. The difference in intake may be important, for vegetarians with additional zinc requirements, including those who are pregnant. Pregnant women are vulnerable to a low zinc status due to the additional zinc demands associated with pregnancy and foetal growth and development, with late pregnancy being the period of greatest need [8]
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