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

Cobalt ions (Co) stabilize HIFα and increase endogenous erythropoietin (EPO) production creating the possibility that Co 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 [Co] 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 Co 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 VO was determined before and after the CoSupp administration period. In the Co group, Hbmass increased by 2.0 ± 2.1% ( < 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 ( = 0.16, = 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 VO did not change, there was a trend for a positive relationship between changes in Hbmass and changes in VO immediately after CoSupp ( = 0.40, = 0.11). Urine [Co] increased from 0.4 ± 0.3 to 471.4 ± 384.1 ng/ml ( < 0.01) and remained significantly elevated until 2 weeks after cessation. An oral Co dosage of 5 mg/day for 3 weeks effectively increases Hbmass with a tendency to increase hemoglobin concentration ([Hb]) and hematocrit (Hct). Because urine Co concentration remains increased for 2 weeks after cessation, upper limit threshold values for monitoring CoSupp can be established.