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Caffeine and diuresis during rest and exercise: A meta-analysis.
Yang Zhang1, Aitor Coca2, Douglas J Casa3
1Chinese Badminton Association, Zhejiang Jiaxing Branch, People's Republic of China.
Journal of Science and Medicine in Sport
|August 27, 2014
Summary
Caffeine has a minor diuretic effect, but exercise negates this. Concerns about fluid loss from caffeine are unwarranted, especially when consumed before physical activity.
Area of Science:
- Sports Medicine
- Human Physiology
- Nutritional Science
Background:
- Caffeine is known for its ergogenic benefits.
- Concerns exist regarding caffeine's potential to increase urine volume and affect hydration during exercise.
- Understanding caffeine's diuretic effect is crucial for athletes and active individuals.
Purpose of the Study:
- To evaluate the diuretic effects of acute caffeine ingestion in adults.
- To assess whether exercise influences caffeine-induced diuresis.
- To determine the impact of caffeine on fluid balance during rest and exercise.
Main Methods:
- A systematic meta-analysis of 16 studies involving healthy adults.
- Inclusion criteria focused on studies providing effect size (ES) data for caffeine's impact on urine volume.
- A random-effects model was used to assess heterogeneity.
Main Results:
- Caffeine ingestion (median 300 mg) increased urine volume by 109 mL (16.0%).
- The diuretic effect was significantly moderated by exercise: minimal effect during exercise (ES=0.10) versus a substantial effect at rest (ES=0.54).
- Females exhibited a greater diuretic response to caffeine than males.
Conclusions:
- Caffeine exerts a minor diuretic effect that is effectively negated by exercise.
- Concerns about significant dehydration due to caffeine consumption before exercise are unfounded.
- Athletes can consume caffeine without undue worry about adverse fluid balance effects when timed appropriately.
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