Zinc absorption from breakfast flakes produced from sprouted or hydrothermally processed wheat: a randomized cross-over human intervention study

Abstract

Zinc (Zn) deficiency is a health issue worldwide. Although wheat is a valuable source of dietary Zn, its bioaccessibility is limited due to chelation with phytic acid. Steeping wheat at 15 °C for 36 h followed by sprouting at 26 °C for 48 h led to 26% phytate reduction and a 1.4-fold increase in Zn bioaccessibility. Hydrothermal processing of wheat at 60 °C and pH 4.0 for 24 h in a 0.1 M sodium citrate buffer reduced phytate content by 48% and increased Zn bioaccessibility 9.9-fold. Here, the potential of sprouting or hydrothermal processing of wheat to increase Zn absorption was studied in a human intervention study using a dual isotope technique in which breakfast flakes were extrinsically labeled with enriched stable isotopes of Zn. One group of participants consumed flakes from untreated and sprouted wheat (test group I, n = 24), whereas another group (test group II, n = 12) consumed flakes from untreated and hydrothermally treated wheat. Sprouting of wheat did not significantly increase fractional Zn absorption, while hydrothermal processing of wheat resulted in a 1.1-fold increase in fractional Zn absorption compared to untreated wheat. The modest if any increase in fractional Zn absorption resulting from sprouting or hydrothermal processing of wheat was likely due to high residual phytate : Zn molar ratios. These findings show that assessing phytate reduction and Zn bioaccessibility values of food products alone is not sufficient to predict Zn absorption from food products.