Dutch Olympic and Non-Olympic Athletes Differ in Knowledge of and Attitudes Toward Third-party Supplement Testing.

Knowledge of third-party testing is important for elite athletes using nutritional supplements to reduce the chances of a positive doping incident. Therefore, we compared the self-reported knowledge and attitudes of  = 601 Dutch Olympic status and non-Olympic status athletes toward an independent Dutch third-party tested system (NZVT) for purchasing nutritional supplements (NSs). Most of the athletes believed that contaminated NSs could lead to a positive doping test (68.0%), and found it unacceptable to use a contaminated NS as a result of incomplete labeling (87.8%). More Olympic status athletes were familiar with the NZVT system (71.1%) than non-Olympic status athletes (24.5%,  < 0.001). Of the athletes knowing about NZVT, Olympic status athletes reported more frequently using the NZVT than non-Olympic athletes (81.7% vs. 50.0%,  < 0.001). Apart from status, more females were familiar with and used the NZVT system for purchasing NSs than males,  < 0.01. In conclusion, many athletes were not familiar with nor used the preferred third-party testing supplement system in the Netherlands when purchasing NSs. While doping warnings and regulations have been in place, considering the risk of unintentional doping use for over two decades, the knowledge of Olympic status and non-Olympic status high-level athletes could still be improved, as many are not reporting the use of third-party testing systems.