Influence of carbohydrate on serum caffeine concentrations following caffeine ingestion

Abstract

Objectives: To examine the effect of a high carbohydrate meal on serum caffeine concentration following caffeine intake. Design: Randomised, double-blind, crossover. Methods: Fourteen healthy males randomly completed 4 trials, each separated by 5 days. Participants either remained fasted (on 2 occasions) or ingested a high carbohydrate meal (2.0gkg-1 carbohydrate, 42.4±0.6kJkg-1) prior to consuming either 6 or 9mgkg-1 anhydrous caffeine. Venous blood was sampled for the analysis of serum caffeine at baseline and at 6 time-points over 4h following caffeine intake. Results: Peak caffeine concentration occurred 60min following ingestion for both the 6 and 9mgkg-1 fasted (p<0.001) trials compared to 120 and 180min following ingestion for the 6 and 9mgkg-1 fed trials, respectively (p<0.001). Peak concentration was greater in the 9mgkg-1 fasted trial than the corresponding fed condition (70±9μmolL-1 and 56±6μmolL-1, respectively) and both were greater than the 6mgkg-1 conditions (44±8μmolL-1 and 38±8μmolL-1 for 6mgkg-1 fasted and fed, respectively). Area under the caffeine curve was significantly greater (p<0.001) in the 9mgkg-1 fasted trial (3262μmolL-1h-1), whilst areas were lowest in the 6mgkg-1 fed trial (1644μmolL-1h-1). Conclusions: A high carbohydrate meal consumed prior to caffeine ingestion significantly reduced serum caffeine concentrations and delayed time to peak concentration. Differences in research findings between caffeine supplementation studies may, at least in part, be related to variations in postprandial timing of caffeine intake. The influence of postprandial timing should be considered when athletes consume caffeine with the aim of enhancing performance. © 2012 Sports Medicine Australia.