Bioavailability of zinc glycinate in comparison with zinc sulphate in the presence of dietary phytate in an animal model with Zn labelled rats

J Anim Physiol Anim Nutr (Berl). 2006 Jun;90(5-6):216-22. doi: 10.1111/j.1439-0396.2005.00583.x.


The objective of this study was to quantify the bioavailability of zinc (Zn) from sulphate and glycinate as representatives of inorganic and organic zinc sources. The semi-synthetic basal diet contained 2 microg/g of native Zn and was fortified with pure sodium-phytate (8 g/kg) in order to simulate conditions of common cereal-based meals. The basal diet was supplemented with either 53 microg/g of Zn from sulphate (control) or 10 microg/g of Zn from either sulphate (ZnSulphate) or glycinate (ZnGly). Twenty-four (65)Zn-labelled, growing rats weighing 133 g were allotted to the three diets (eight animals per treatment) and were kept pair-fed to ZnSulphate for 15 days. Zn contents in blood plasma, femur and whole body, as well as, plasma alkaline phosphatase activities were reduced compared with control indicating a zinc deficiency in ZnSulphate and ZnGly treatment. This allowed their differentiation in zinc bioavailability. True absorption of dietary Zn was significantly higher in ZnGly than in ZnSulphate (51% vs. 44%) while losses of endogenous faecal Zn and urinary Zn were not affected to a quantitatively relevant extent (mean: 17% and 2% of intake). This resulted in a +30% significantly improved Zn retention for ZnGly (33% vs. 25%) and a lower severity on Zn deficiency symptoms compared with ZnSulphate. Metabolic utilization accounted for 95% of absorbed dietary Zn for both Zn sources. Overall, the bioavailability of zinc glycinate was significantly superior by 16% to zinc sulphate (49% vs. 42%), mainly because of a higher absorptive potential at presence of a strong anti-nutritive component (phytate) in the diet.

MeSH terms

  • Animal Feed
  • Animal Nutritional Physiological Phenomena
  • Animals
  • Biological Availability
  • Feces / chemistry
  • Glycine / analogs & derivatives*
  • Glycine / pharmacokinetics
  • Intestinal Absorption / drug effects*
  • Phytic Acid / pharmacology*
  • Random Allocation
  • Rats
  • Rats, Sprague-Dawley
  • Urinalysis / veterinary
  • Zinc / deficiency
  • Zinc Radioisotopes
  • Zinc Sulfate / pharmacokinetics*


  • Zinc Radioisotopes
  • zinc glycinate
  • Zinc Sulfate
  • Phytic Acid
  • Zinc
  • Glycine