No Effects of Organic and Conventional Diets on Intake and Absorption of Zinc and Copper in Men – Evidence from Two Cross-over Trials Using Stable Enriched Isotopes

Abstract

Organic foods have been repeatedly claimed to have a superior nutrient content. However, effects of production method on absorption of nutrients in vivo remains understood. Our aim was to investigate the effects of organic and conventional diets on intake and absorption of zinc and copper in humans. A double-blind, cross-over, intervention trial (3 dietary periods of 12 days, separated with 2-week-long wash-out periods) was performed in 2008 (n=17) and 2009 (n=16) in young men. The diets were based on 9 crops grown in 2 organic and 1 conventional systems in 2 replications over 2 years. Primary outcomes were intake and apparent absorption of zinc and copper. The absorption was determined by fecal excretion of stable enriched isotopes extrinsically added to the entire menu. Within each year, intake and absorption of zinc (overall mean ± SD 12.35 ± 0.47 mg 10MJ-1 and 44.6% ± 12.1, respectively) and copper (overall mean ± SD 2.12 ± 0.28 mg 10MJ-1 and 41.2% ± 13.2, respectively) were not significantly different between the organic and conventional diets. Growing season had no effect on zinc intake and absorption. However, in 2008 copper intake was higher (P=0.01) and absorption lower (P<0.005) compared with 2009 (mean absorption ± SD; 35.3% ± 13.5 in 2008 and 54.0% ± 10.7 in 2009). Zinc and copper were well absorbed from the investigated diets. The consumption of organic diets did not improve apparent absorption of these trace elements compared with the conventional diets