Caffeine in sport. Urinary excretion of caffeine in healthy volunteers after intake of common caffeine-containing beverages.
The presence of a concentration of caffeine greater than or equal to 15 micrograms/ml in urine of athletes participating in competitive sport is a disqualifying factor. A study was conducted to establish how much caffeine needs to be ingested--in the form of coffee, tea or Coca-Cola--to approach or exceed this limit. Nine healthy volunteers participated in a randomised cross-over study and received caffeine in the form of these beverages, ingested within 15 minutes, in doses ranging from 1.52 mg/kg to 17.53 mg/kg. The latter dose is equivalent to nearly 8 cups of ordinary percolated coffee. The maximum caffeine concentration in urine recorded was 14 micrograms/ml, 3 hours after ingestion. A significant correlation was found between the caffeine dose and the maximum urinary concentration. The mean recovery of caffeine in urine was between 0.74% and 0.91% of the administered dose. The nature of the beverage did not appear to influence the degree of caffeine excretion. It is concluded that if a concentration of 15 micrograms caffeine/ml urine is recorded, it can safely be accepted that the athlete purposely ingested large amounts of the substance, in whatever form.
van der Merwe
P J
PJ
Department of Pharmacology, University of the Orange Free State, Bloemfontein.
Müller
F R
FR
Müller
F O
FO
D000293:Adolescent; D000328:Adult; D002110:Caffeine / Q000008:administration & dosage / Q000652:urine*; D002253:Carbonated Beverages / Q000032:analysis; D003069:Coffee; D004300:Doping in Sports; D006801:Humans; D008297:Male; D011897:Random Allocation; D012016:Reference Values; D013662:Tea; D013997:Time Factors
D003069:Coffee; D013662:Tea; D002110:Caffeine