The bottom line: As zinc binds to protein, absorption of zinc is largely dependent on protein intake, especially proteins derived from animals. The amount of protein in the diet is a major factor contributing to efficiency of zinc absorption and evidence suggests that vegetarians are at higher risk of zinc deficiency. Taking a zinc supplement with protein, such as a protein-rich meal, or whey protein isolate may substantially increase bioavailability by enhancing absorption.
Zinc is available to be consumed in the diet from both plant and animal sources. The recommended dietary intake (RDI) for vegetarians is 12 mg/day for women and 21 mg/day for men. Based on the lower bioavailability of zinc from a vegetarian diet, this is 150% of the RDI for the general Australian population.
Lean red meat, wholegrain cereals and legumes provide the highest concentrations of zinc (generally in the range of 2.5–5.0 mg/100 g raw weight). Unrefined whole grains provide a higher concentration of zinc compared to refined grains due to zinc being contained in the outer layers of the grains (up to 5.0 mg/100 g, compared with 1.0 mg/100 g).
Dietary sources of zinc that are important for all Australians (not just vegetarians), include, wholegrain breads and cereals, rolled oats, brown rice, nuts, seeds, legumes, tofu/soy products and fortified foods. Fruit and green leafy vegetables have much lower concentrations of zinc due to their high water content.
The daily requirement for vegetarians has been set at 1.5 times the zinc requirement of the general population due to the higher content of phytate which typically decreases the absorption of zinc in vegetarian diets. A well planned vegetarian diet can reach sufficient amounts of zinc for all age groups.
References:
1. Australian Health Survey: Usual Nutrient Intakes, 2011-12 financial year [Internet]. Australian Bureau of Statistics. 2021 [cited 17 May 2021]. Available from: https://www.abs.gov.au/statistics/
2. Saunders A. 2013. Zinc and Vegetarian Diets. The Medical Journal of Australia. Available from: https://www.mja.com.au/