Effects of 3 Weeks of Oral Low-Dose Cobalt on Hemoglobin Mass and Aerobic Performance

Effects of 3 Weeks of Oral Low-Dose Cobalt on Hemoglobin Mass and Aerobic Performance / Torben Hoffmeister, Dirk Schwenke, Oliver Krug, Nadine Wachsmuth, Hans Geyer, Mario Thevis, William C. Byrnes, Walter F. J. Schmidt. - (Frontiers in Physiology (2019) 9 (19 September) ; p. 1-9).
- PMID: 30283349.
- PMCID: PMC6157393.
- DOI: 10.3389/fphys.2018.01289


Introduction: Cobalt ions (Co2+) stabilize HIFα and increase endogenous erythropoietin (EPO) production creating the possibility that Co2+ supplements (CoSupp) may be used as performance enhancing substances. The aim of this study was to determine the effects of a small oral dosage of CoSupp on hemoglobin mass (Hbmass) and performance with the objective of providing the basis for establishing upper threshold limits of urine [Co2+] to detect CoSupp misuse in sport.

Twenty-four male subjects participated in a double-blind placebo-controlled study. Sixteen received an oral dose of 5 mg of ionized Co2+ per day for 3 weeks, and eight served as controls. Blood and urine samples were taken before the study, during the study and up to 3 weeks after CoSupp. Hbmass was determined by the CO-rebreathing method at regular time intervals, and VO2max was determined before and after the CoSupp administration period.

In the Co2+ group, Hbmass increased by 2.0 ± 2.1% (p < 0.001) while all the other analyzed hematological parameters did not show significant interactions of time and treatment. Hemoglobin concentration ([Hb]) and hematocrit (Hct) tended to increase (p = 0.16, p = 0.1) and also [EPO] showed a similar trend (baseline: 9.5 ± 3.0, after 2 weeks: 12.4 ± 5.2 mU/ml). While mean VO2max did not change, there was a trend for a positive relationship between changes in Hbmass and changes in VO2max immediately after CoSupp (r = 0.40, p = 0.11). Urine [Co2+] increased from 0.4 ± 0.3 to 471.4 ± 384.1 ng/ml (p < 0.01) and remained significantly elevated until 2 weeks after cessation.

An oral Co2+ dosage of 5 mg/day for 3 weeks effectively increases Hbmass with a tendency to increase hemoglobin concentration ([Hb]) and hematocrit (Hct). Because urine Co2+ concentration remains increased for 2 weeks after cessation, upper limit threshold values for monitoring CoSupp can be established.

Original document


Research / Study
19 September 2018
Byrnes, William C.
Geyer, Hans
Hoffmeister, Torben
Krug, Oliver
Schwenke, Dirk
Thevis, Mario
Wachsmuth, Nadine
United States of America
Other organisations
Universität Bayreuth - University of Bayreuth
University of Colorado Boulder (CU Boulder)
Cologne, Germany: Institute of Biochemistry - German Sport University Cologne
Kreischa, Germany: Institute of Doping Analysis and Sports Biochemistry (IDAS)-Dresden
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New substance, not on prohibited list
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S2. Peptide Hormones, Growth Factors
Erythropoietin (EPO)
Medical terms
Endogenous production
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Scientific article
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Date generated
27 March 2019
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