Sport nutritional supplements: quality and doping controls.

Nutritional supplements are part of the diet of many athletes. With the exception of caffeine and ephedrine alkaloids, most of these products do not contain substances that are prohibited to competing sportsmen. In recent years, androgens, pro-hormones such as DHEA, androstenedione, androstenediol and 19-norsteroids became available for oral self-administration in many countries and on the Internet. Their claimed actions, efficiency or potency, and the possible adverse effects have not been thoroughly investigated by controlled clinical studies. Some products were shown to contain prohibited substances such as ephedrine, caffeine, or steroids, that were not listed on the label. Urine samples collected after the administration of these supplements can test positive. The administration of natural steroids such as testosterone and its precursors cannot be proven by the sole identification of the substances in the urine. The approach to detection is based upon the deviation of selected parameters of the metabolic profiles from the range of values normally found in humans. The individual's norm is also studied to exclude the few cases of systematic and natural excretion of extreme values. The combination of the GC/MS and the GC/C/IRMS offers a powerful tool to discriminate between the natural and synthetic origin of the urinary steroids.