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J Sci Med Sport. 2015 Sep;18(5):569-74. doi: 10.1016/j.jsams.2014.07.017. Epub 2014 Aug 9.

Caffeine and diuresis during rest and exercise: A meta-analysis.

Author information

1
Chinese Badminton Association, Zhejiang Jiaxing Branch, People's Republic of China. Electronic address: dr.zhang.yang@qq.com.
2
National Personal Protective Technology Laboratory, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, United States.
3
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, United States.
4
Farquhar College of Arts and Sciences, Exercise and Sports Science, Nova Southeastern University, United States.
5
Department of Health, Physical Education and Recreation, University of North Alabama, United States.
6
Department of Kinesiology, University of Alabama, United States.

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:

Coffee; Dehydration; Diuretic; Fluid balance; Methylxanthine

PMID:
25154702
PMCID:
PMC4725310
DOI:
10.1016/j.jsams.2014.07.017
[Indexed for MEDLINE]
Free PMC Article

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