Contamination in Nutritional Supplements: Why Anti-Doping Certification Matters

Professional athletes are subjected to a heavy physical workload. Their nutritional requirements are therefore higher than those of the general population, for both macronutrients and micronutrients (vitamins and minerals), which means supplementation is often necessary when diet alone cannot meet them. In addition, to maximize performance, many athletes turn to other nutritional supplements. Some have strong scientific evidence supporting their effectiveness—for example, creatine or caffeine—but other supplements lack established validity. In response to this demand, a huge number of sports-supplement brands now exist. However, the uncontrolled growth of this market has also increased the risk of what the World Anti-Doping Agency calls “inadvertent doping.” This refers to substances not declared by the manufacturer, which can have dramatic consequences for athletes, either by causing a positive doping test or even by endangering their health. Although it may sound unlikely, inadvertent doping is much more prevalent in sport than we might think. A review estimated that between 6 and 9% of doping cases result from consuming nutritional supplements that contain prohibited substances (1). In fact, a more recent study suggests that as many as 14% of doping cases occurring between 2003 and 2020 could be attributable to the use of nutritional supplements (2).

The presence of prohibited substances in nutritional supplements is therefore highly concerning and, unfortunately, very prevalent. According to a study that analyzed 66 products sold through different Danish websites from 21 brands—including products for fat loss, muscle gain and others claiming to provide energy—38% contained an undeclared substance that could trigger a positive doping test, primarily stimulants and anabolic steroids. In fact, nearly 5% of the products could even be considered harmful to health (3). These findings are not isolated. For example, a review analyzing a total of 23 studies that included supplements such as protein powders, creatine, multivitamins and energy drinks found an alarming contamination rate of 12-58% among these products (4). The authors therefore concluded that it is common to find small amounts of stimulants (e.g., ephedrine) or anabolic substances (e.g., testosterone, androsterone or nandrolone) that are prohibited by the World Anti-Doping Agency and carry a high health risk, whether because of deficient quality control—for example, contamination during manufacturing or processing—or intentional adulteration.

Given these findings, educating athletes about the importance of monitoring the supplements they take is essential, particularly ensuring that these products are prescribed and supervised by nutrition professionals. Beyond reviewing nutrition labels, we must also make sure that supplements pass all necessary quality controls. When choosing nutritional supplements, it is therefore advisable to select products certified by an independent company rather than the manufacturer itself. This is the case with supplements carrying Informed Sportcertification, a food-supplement testing program that certifies the absence of contamination by substances prohibited in sport, providing assurance that the supplement consumed by the athlete belongs to a tested batch certified as “free from prohibited substances.”

AUTHOR

Pedro Valenzuela
Researcher at the University of Castilla-La Mancha
Website: www.fissac.com

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References

1.          Outram S, Stewart B. Doping through supplement use: A review of the available empirical data. Int J Sport Nutr Exerc Metab. 2015;25(1):54–9.

2.          Lauritzen F. Dietary Supplements as a Major Cause of Anti-doping Rule Violations. Front Sport Act Living. 2022;4(March):1–7.

3.          Duiven E, van Loon LJC, Spruijt L, Koert W, de Hon OM. Undeclared doping substances are highly prevalent in commercial sports nutrition supplements. J Sport Sci Med. 2021;20(2):328–38.

4.          Martínez-Sanz JM, Sospedra I, Ortiz CM, Baladía E, Gil-Izquierdo A, Ortiz-Moncada R. Intended or unintended doping? A review of the presence of doping substances in dietary supplements used in sports. Nutrients. 2017;9(10):1–22.