Professional athletes are subjected to high physical demands. As a result, their nutritional needs exceed those of the general population, both in terms of macronutrients and micronutrients (vitamins and minerals). This often makes supplementation necessary when dietary intake alone is insufficient. Additionally, in the pursuit of peak performance, many athletes turn to nutritional supplements—some of which are strongly supported by scientific evidence (e.g., creatine or caffeine), while others lack proven efficacy.
Due to this demand, there is currently an overwhelming number of sports supplement brands. However, the uncontrolled growth of this market has also led to an increased risk of what the World Anti-Doping Agency (WADA) calls “unintentional doping.” This refers to the presence of substances not listed by the manufacturer, which can have severe consequences for athletes, including testing positive for doping or facing potential health hazards.
Although it may seem unlikely, unintentional doping is more common in the sports world than many might expect. A review estimated that 6–9% of doping cases are due to the use of supplements containing banned substances (1). A more recent study even suggests that up to 14% of doping cases between 2003 and 2020 may be attributable to supplement use (2).
The presence of banned substances in nutritional supplements is therefore highly concerning and, unfortunately, widespread. For instance, a study that analyzed 66 products from Danish websites representing 21 different brands—including fat loss, muscle gain, and energy-boosting products—found that 38% contained undeclared substances that could lead to a positive doping test. These included mainly stimulants and anabolic steroids. Alarmingly, about 5% of the products could even be considered harmful to health (3).
And this is not an isolated finding. A review that examined 23 studies analyzing products like protein powders, creatine, multivitamins, and energy drinks found a disturbing contamination rate ranging from 12% to 58% (4). The authors concluded that it’s common to find small amounts of stimulants (e.g., ephedrine) or anabolic substances (e.g., testosterone, androsterone, or nandrolone), which are prohibited by WADA and pose serious health risks. These issues may result from poor quality control (e.g., contamination during manufacturing or processing) or even intentional adulteration.
In light of these findings, it is essential to educate athletes about the importance of monitoring the supplements they take—especially ensuring that these are recommended and supervised by qualified nutrition professionals. Beyond simply checking the nutrition labels, it’s crucial to ensure that any supplement consumed has undergone all necessary quality controls. This is why, when choosing nutritional supplements, it is advisable to opt for those certified by an independent third party rather than the manufacturer itself.
One such certification is Informed Sport, a quality assurance program that tests dietary supplements for banned substances in sport. It guarantees that the product consumed by the athlete is part of a batch that has been tested and certified as “free from doping substances.”
AUTHOR
Pedro Valenzuela
Researcher at the University of Castilla-La Mancha
Website: www.fissac.com
