A 2018 Study found that none of 33 supplements analysed contained any of 284 substances that feature on the World Anti-Doping Agency’s (WADA) Prohibited List. The Study, conducted by Anti-Doping Denmark (ADD), Team Denmark, the Danish Food & Drug Administration, and the Danish Medicines Agency, involved 33 samples of which 20 were produced abroad. 

Six of the products were registered with the Danish Food Administration and six were considered registered dietary supplements. The remaining were considered ordinary foods. On initial screening, two of the products returned trace findings for tuaminoheptane and one returned a trace finding for nicotine. Using a ‘confirmation analysis’ procedure on the products containing tuaminoheptane, which is prohibited, both initial findings were eliminated.

“We cannot, on the basis of this Study, say that all supplements sold in Denmark are free of doping substances”, said Jakob Mørkeberg, a Scientific Advisor to ADD, in a statement. “Our recommendation that athletes should exercise great caution when using supplements and products targeted at sport is unchanged”.

It is important to point out that the Prohibited List is not an exhaustive document, as it doesn’t list all the substances WADA considers prohibited. It contains statements prohibiting substances ‘with a similar chemical structure or similar biological effect(s)’; also ‘All selective and non-selective beta-2 agonists,including all optical isomers, are prohibited. Including, but not limited to [lists examples]’. 

As such, athletes could find themselves banned for a substance that doesn’t feature on the List, but has a similar chemical structure to one that does feature. In 2016, Liverpool footballer Mamadou Sakho was provisionally suspended after returning an adverse analytical finding for higenamine, which was not featured on the List at the time, after using a sports supplement. He is now taking legal action against WADA.