Zinc bioavailability is improved by the micronised dispersion of zinc oxide with the addition of L-histidine in zinc-deficient rats

Abstract

Zinc fortification of milk or soft drinks is usually used to combat zinc deficiencies in developing countries. Water-soluble zinc compounds, such as zinc sulfate or zinc citrate, are better absorbed but have an unacceptable taste. A micronised, dispersible zinc oxide (MDZnO), which does not have such a problem concerning taste, had higher solubility compared to ZnO (zinc oxide) in an artificial gastric solution. MDZnO was tested for its bioavailability using zinc-deficient Wistar rats. Prior to the experiment, rats were fed zinc-deficient diet for 3 wk and were orally administered control (distilled water) or zinc solutions (ZnO, ZnO+L-histidine (His), MDZnO, MDZnO+His, 1 mg zinc/kg or 3.2 mg His/kg body weight). Compared to ZnO, MDZnO showed a lag in peak time and a lengthy period of continued high plasma zinc concentration after the single oral administration of zinc compounds. Addition of His to MDZnO elevated serum zinc concentration. Serum zinc concentration (area under the curve) in rats administered MDZnO with His was significantly higher than in rats administered distilled water (p<0.05). Liver zinc level was significantly higher in rats administered MDZnO with His compared with control rats (p<0.05), although the level was not affected by the administration with ZnO alone, ZnO+His, or MDZnO alone. In conclusion, the solubility of ZnO was elevated by the micronised dispersion tecnique and an in vivo study using zinc-deficient rats confirmed that its bioavailability was significantly improved compared to ZnO and the coadministration of His additively enhanced the bioavailability of MDZnO.