Journal Title (Medline/Pubmed accepted abbreviation): Appl Physiol Nutr Metab
Page numbers: 555-561
Background: Evidence has shown that caffeine has ergogenic effects in a variety of sports, and therefore, it was listed as a doping agent in 1984 (limit, 12 μg/mL urine). However, because a threshold level cannot be established to distinguish social use vs abuse, caffeine was removed as a prohibited substance in 2004 by the World Antidoping Agency (WADA).
Hypothesis: Caffeine use was expected to have progressively increased following the 2004 removal as a doping agent.
Subjects: 20,686 urinary samples from 2004 to 2008 received by the Spanish Anti-doping Laboratory following national and international competitions of > 62 sport specialities (2004, 3,262 samples; 2005, 4,911 samples; 2006, 4,710 samples; 2007, 4,960 samples; 2008, 2,843 samples) were analyzed.
Experimental design: Observational
Treatments and protocol: Caffeine was measured using gas chromatography-mass spectrometry, with calibration for each batch analyzed. Between-days reproducibility, accuracy, and uncertainty were evaluated. Limit of detection was 0.1 μg/mL, and samples below detection limit were considered caffeine free.
Although caffeine is no longer prohibited by WADA, it appears that caffeine use did not increase. Men and women have similar caffeine usage (per kg body weight), but older athletes have a higher usage than younger athletes. In addition, athletes in endurance sports had a higher caffeine usage compared with athletes in intermittent sports. One explanation for the minimal change in caffeine usage is that the limit was not restrictive enough to limit performance enhancement (enhancement has been shown at urinary concentrations as low as 4 μg/mL). Moreover, maximal performance enhancement from caffeine consumption usually results in urinary concentrations < 12 μg/mL.