Evaluation of new techniques for zinc and cortisol assessment with a placebo-controlled zinc supplementation trial in a subsample of Ethiopian women

Abstract

Scope and Method of Study:

The placebo-controlled zinc supplementation (20 mg zinc daily) study investigated the changes in plasma zinc levels, as well as other health and stress parameters at baseline and endpoint of the 17 day trial. In addition, a novel method quantifying changes in zinc transporter Zip 4 mRNA expression due to increased dietary zinc intake was tested. Additionally, the correlation between the newer salivary cortisol measurement to the established urine and serum cortisol measures was tested. The effect of changes in zinc intake on DNA integrity was evaluated employing the comet assay.

Findings and Conclusions:

No significant intervention effect on plasma zinc or other measured health or stress parameters could be identified. The volunteers were within normal ranges for the parameters assessed in this study, except for their moderate iodine deficiency. Due to the fact that not enough mRNA could be extracted from the samples, the developed method could not be tested with the samples obtained in the field. Saliva cortisol did correlate with the urinary cortisol levels; however, a quarter of the volunteers had saliva cortisol concentrations were slightly above normal range of the test kit, while all urine and serum samples were within normal range. The comet assay revealed that zinc supplementation significantly decreased DNA breaks.