RDA for Zinc May Need to Increase
Reviewed by: Alan Gaby, M.D.
Author: Armah SM
Reference: Fractional zinc absorption for men, women, and adolescents is overestimated in the current Dietary Reference Intakes. J Nutr 2016;146:1276-1280.
Design: Assessment of zinc absorption
Participants: Participants in the National Health and Nutrition Examination Survey (NHANES) 2009-2010.
Study Medication and Dosage: N/A
Primary Outcome Measure: Estimated percent zinc absorption by healthy volunteers.
Key Findings: Using nutrient intake data from NHANES 2009-2010 and applying 2 algorithms that estimated percent zinc absorption as a function of the molar ratio of phytate to zinc in the diet, the authors concluded that the Recommended Dietary Allowances (RDAs) for both men and women need to be increased by nearly one-half of the current values in order to meet their requirements for absorbed zinc.
Practice Implications: Estimates of zinc absorption that were used to establish the current RDAs for zinc were based on data from published studies. However, the inhibitory effect of phytate on zinc absorption was underestimated because of the low phytate content of the semi-purified diets used in these studies. The results of the present study suggest that the RDA for zinc should be increased by nearly 50%. Interestingly, the RDA for zinc was 15 mg per day in the 1980s, but was later reduced to 11 mg per day for men and 8 mg per day for women.
In most studies of healthy adolescents and adults of various ages consuming Western diets, mean zinc intake ranged from 7.3 mg per day to 10.4 mg per day. Thus, a substantial proportion of the population is failing to meet even the current RDA for zinc. If, as the present study suggests, the RDA should be increased, then the great majority of people in the United States would need to take a zinc supplement. Groups at risk of having marginal or low zinc intake include pregnant women, teenage and college women, elderly or institutionalized individuals, people with low income, and vegetarians.