Abstract
Objectives
Although ergogenic, acute caffeine ingestion may increase urine volume, prompting
concerns about fluid balance during exercise and sport events. This meta-analysis
evaluated caffeine induced diuresis in adults during rest and exercise.
Design
Meta-analysis.
Methods
A search of three databases was completed on November 1, 2013. Only studies that involved
healthy adults and provided sufficient information concerning the effect size (ES)
of caffeine ingestion on urine volume were included. Sixteen studies met the inclusion
criteria, providing a total of 28 ESs for the meta-analysis. Heterogeneity was assessed
using a random-effects model.
Results
The median caffeine dosage was 300 mg. The overall ES of 0.29 (95% confidence interval (CI) = 0.11–0.48, p = 0.001) corresponds to an increase in urine volume of 109 ± 195 mL or 16.0 ± 19.2% for caffeine ingestion vs. non-caffeine conditions. Subgroup meta-analysis confirmed
exercise as a strong moderator: active ES = 0.10, 95% CI = −0.07 to 0.27, p = 0.248 vs. resting ES = 0.54, 95% CI = 0.22–0.85, p = 0.001 (Cochran's Q, p = 0.019). Females (ES = 0.75, 95% CI = 0.38–1.13, p < 0.001) were more susceptible to diuretic effects than males (ES = 0.13, 95% CI = −0.05 to 0.31, p = 0.158) (Cochran's Q, p = 0.003).
Conclusions
Caffeine exerted a minor diuretic effect which was negated by exercise. Concerns regarding
unwanted fluid loss associated with caffeine consumption are unwarranted particularly
when ingestion precedes exercise.
Keywords
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Article info
Publication history
Published online: August 08, 2014
Accepted:
July 31,
2014
Received in revised form:
May 7,
2014
Received:
February 15,
2014
Identification
Copyright
© 2014 Sports Medicine Australia. Published by Elsevier Inc. All rights reserved.
