Caffeine in sport. Urinary excretion of caffeine in healthy volunteers after intake of common caffeine-containing beverages.

  • 20 August 1988
    • journal article
    • clinical trial
    • Vol. 74  (4) , 163-4
Abstract
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.

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