Their findings on the steroids, which were not listed on the supplement labels, were published in the International Journal of Sport Nutrition and Exercise Metabolism.
Anabolic steroids, or androgens, pose a possible health risk to their users. Athletes who use them are likely to fail doping tests and therefore, be banned from competition.
The researchers bought 116 over-the-counter sports supplements that were marketed as ‘performance-enhancing’ from several different retailers in Australia, selecting only products that did not have any androgens listed on their labels.
The supplements included vitamins, herbal extracts, fat metabolisers, pre-workout formulations, and protein powders.
They subsequently found that 5.4% of the supplements tested positive for androgens, meaning that “more than one in 20 contained anabolic steroids that the users would be unaware of if they were relying on information on their labels”.
Team leader Professor Alison Heather, from the University of Otago School of Biomedical Sciences’ physiology department, said it was too early to tell if the contamination of the supplements is due to adulteration or substandard manufacturing.
They are now undergoing more tests to determine exactly which androgens are contaminating them, before the team contacts the companies responsible with the results.
Heather said: "Supplements can contain ingredients that may have useful properties. However, due to poor manufacturing practices or adulteration, sports supplements can contain compounds that are banned for use in sports, but that are not included on the label as an ingredient.”
A 2014 report stated that 70% of the New Zealand first XV rugby players regularly consumed supplements. According to a 2015 report, 95% of elite Kiwi athletes took supplements.
Heather revealed, “Our research shows that there is a real risk for health and doping violations that athletes must consider when taking sports supplements, even those sold over the counter.”
The paper concluded: "The findings reinforce the need to increase awareness of the dangers of nutritional supplements and highlight the challenges that clinicians face in the fast-growing market of nutritional supplements."
In addition to finding out which androgens the abovementioned supplements contain, Heather and her team are in the process of developing a first-of-its-kind test for anti-doping agencies, which could be ready within a year.
At present, anti-doping agencies test athletes for a specific set of illegal substances and masking agents. The new test, however, will detect the presence of any anabolic steroid or androgenic substance and its biological effects in the human body, regardless of its chemical structure or the type of drug taken.
While testing is currently carried out in a laboratory, Heather said the team was working on a more user-friendly version for agencies to use on athletes in order to detect anabolic steroid use in a cellular context, therefore eliminating the need for different tests for different types of steroids.
She said: "We hope to have that ready in 12 to 15 months."