Original Article
European Journal of Clinical Nutrition advance online publication 19 September 2007; doi: 10.1038/sj.ejcn.1602899
Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement
Contributors: KK managed the realization of the study, sample and statistical analysis and interpretation of the results and led the writing of the paper. MKP initiated the trial, was in charge of the design and the implementation and contributed to the writing. HG, JM and WS instigated the study and assisted with the interpretation of the data and the preparation of the manuscript.
K Koehler1, M K Parr1, H Geyer1, J Mester2 and W Schänzer1
- 1Institute of Biochemistry, German Research Centre of Elite Sport, German Sport University Cologne, Cologne, Germany
- 2Institute of Training Science and Sport Informatics, German Research Centre of Elite Sport, German Sport University Cologne, Cologne, Germany
Correspondence: K Koehler, Institute of Biochemistry, German Research Centre of Elite Sport, German Sport University Cologne, Carl-Diem-Weg 6, Cologne 50933, Germany. E-mail: k.koehler@biochem.dshs-koeln.de
Received 23 November 2006; Revised 10 April 2007; Accepted 25 July 2007; Published online 19 September 2007.
Abstract
Objectives:
To investigate whether the administration of the zinc-containing nutritional supplement ZMA causes an increase of serum testosterone levels, which is an often claimed effect in advertising for such products; to monitor the urinary excretion of testosterone and selected steroid hormone metabolites to detect potential changes in the excretion patterns of ZMA users.
Subjects:
Fourteen healthy, regularly exercising men aged 22–33 years with a baseline zinc intake between 11.9 and 23.2 mg day-1 prior to the study.
Results:
Supplementation of ZMA significantly increased serum zinc (P=0.031) and urinary zinc excretion (P=0.035). Urinary pH (P=0.011) and urine flow (P=0.045) were also elevated in the subjects using ZMA. No significant changes in serum total and serum free testosterone were observed in response to ZMA use. Also, the urinary excretion pattern of testosterone metabolites was not significantly altered in ZMA users.
Conclusions:
The present data suggest that the use of ZMA has no significant effects regarding serum testosterone levels and the metabolism of testosterone in subjects who consume a zinc-sufficient diet.
Keywords:
zinc supplementation, athletes, serum testosterone, urinary steroid hormone metabolites, urinary zinc excretion