Vegetarian diets across the lifecycle: impact on zinc intake and status

Optimal zinc status is an important consideration when evaluating the nutritional adequacy of vegetarian diets. In the absence of animal tissue sources of zinc and with increased intake of inhibitors of zinc absorption, phytic acid in particular, the bioavailability of zinc is thought to be lower from vegetarian as compared to omnivorous diets. The aim of this chapter is to review the research that examines the effects of vegetarian compared to omnivorous diets on zinc intake and zinc status in the elderly, adults, children, pregnancy, and lactation. A narrative review of the published literature was undertaken, focusing on observational studies in humans that reported zinc intake and biomarkers of zinc status at various stages of the life cycle. Compared to their respective nonvegetarian control groups, adult male and female vegetarians have lower dietary zinc intakes and serum zinc concentrations. However in the elderly, children, and in women during pregnancy and lactation, there is insufficient evidence to determine whether zinc intake and status are lower in vegetarians compared to omnivores. Inconsistencies in study findings reflect variations inherent in the definition of vegetarian diets, and in many instances compromised statistical power due to a small sample size. Improved methods for the assessment of zinc status are required to determine whether homeostatic responses are sufficient to maintain an adequate zinc status in vegetarians, particularly during times of increased requirement. Appropriate dietary advice to increase the zinc content and bioavailability of vegetarian diets throughout the life cycle is prudent.