"Although it is difficult to quantify the extent of the problem, it is estimated that 6.4% to 8.8% of doping cases are caused by tainted dietary supplements."
There was a case of cross-contamination of vitamin tablets with steroids using the same production line.26 The amount of contamination does not have to be great to cause an abnormal doping test. One capsule of a tainted dietary supplement resulted in all having urinary levels of steroid metabolites above the WADA threshold.81 Ingestion of as little as 2.5 µg of 19-norandrostendione, a steroid prohormone, in a dietary supplement (0.00005% contamination) can result in transient elevations of metabolite in urine to fail a doping test.83
Starting in 2000, the first solid evidence for steroid contamination of dietary supplements showed that of 634 nonhormonal dietary supplements from 13 countries and 215 suppliers, 14.8% were contaminated with hormones or prohormones.
Determining whether a specific product contains AAS is difficult without chemical analysis.26 Ingestion of designer steroids has produced positive doping tests in many unsuspecting athletes.54 Once the new AAS is identified and reported to the FDA, the new compound is banned by DEA/FDA, and often, a new compound emerges in the marketplace to replace it.
More recently, other substances have been developed, such as selective androgen receptor modulators, which are nonsteroidal alternatives to activate the androgen receptors on muscle and bone tissue.69 New analytical methods for their detection have been developed since 2006. As with designer steroids, newer substances are constantly entering the supplement market and are a substantial concern for misuse.28