Zinc-Biofortified Wheat Intake and Zinc Status Biomarkers in Men: Randomized Controlled Trial

Abstract

ABSTRACT Background Biofortification is a novel method for improving the nutritional value of grains. Wheat is widely consumed worldwide. Thus, wheat zinc biofortification may improve the zinc status of populations. Objectives We determined the effect of consuming zinc-biofortified wheat on plasma zinc concentrations and biomarkers of zinc-dependent functions in a controlled feeding study. Methods Thirty-six healthy adult men, aged 18 to 51 y, participated in a 10-wk zinc-controlled feeding trial. After a 2-wk run-in period [metabolic period (MP) 1] (9.3 mg zinc/d and 2.1 g total phytate/d) to standardize zinc status, the participants consumed bread made from zinc-biofortified wheat (10.9 mg zinc/d) with no additional phytate (0.6 g/d total phytate) for 6 wk (MP2). During the final 2 wk (MP3), half of the men took a 25-mg zinc supplement daily to determine if the supplement further altered zinc status biomarkers. Repeated-measures linear regression methods were used to compare plasma zinc concentrations, fatty acid desaturase (FADS) activities, glutathione (GSH) concentrations, and DNA strand breaks assessed at enrollment and the end of each metabolic period. Results Plasma zinc concentrations did not change throughout the study. From the end of MP1 to the end of MP2, the conversion of linoleic acid to γ-linolenic acid (FADS2 activity) increased from 0.020 to 0.025 (P = 0.02), and the conversion of dihomo-γ-linolenic acid to arachidonic acid (FADS1 activity) decreased from 6.37 to 5.53 (P = 0.01). GSH concentrations and DNA strand breaks did not change. Zinc supplementation (25 mg/d) in MP3 did not alter any of the endpoints. Conclusions In healthy adult men, a 1.6-mg/d increase in dietary zinc from biofortified wheat modified FADS2 and FADS1 activities without changing DNA damage, plasma zinc, or GSH concentrations, demonstrating that FADS activities are more sensitive to small changes in zinc consumed with a meal. This trial was registered at clinicaltrials.gov as NCT03451214.