Zhang Yang, Coca Aitor, Casa Douglas J, Antonio Jose, Green James M, Bishop Phillip A
Chinese Badminton Association, Zhejiang Jiaxing Branch, People's Republic of China.
National Personal Protective Technology Laboratory, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, United States.
J Sci Med Sport. 2015 Sep;18(5):569-74. doi: 10.1016/j.jsams.2014.07.017. Epub 2014 Aug 9.
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.
Meta-analysis.
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.
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).
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.
尽管咖啡因具有促力作用，但急性摄入咖啡因可能会增加尿量，这引发了人们对运动和体育赛事期间液体平衡的担忧。这项荟萃分析评估了成年人在休息和运动期间咖啡因诱导的利尿作用。
荟萃分析。
于2013年11月1日完成了对三个数据库的检索。仅纳入了涉及健康成年人且提供了关于咖啡因摄入对尿量影响大小（ES）的充分信息的研究。16项研究符合纳入标准，为荟萃分析提供了总共28个效应大小。使用随机效应模型评估异质性。
咖啡因的中位剂量为300毫克。总体效应大小为0.29（95%置信区间（CI）=0.11 - 0.48，p = 0.001），这对应于与非咖啡因摄入情况相比，咖啡因摄入使尿量增加109±195毫升或16.0±19.2%。亚组荟萃分析证实运动是一个强大的调节因素：运动时的效应大小=0.10，95% CI = -0.07至0.27，p = 0.248，而休息时的效应大小=0.54，95% CI = 0.22 - 0.85，p = 0.001（ Cochr an's Q，p = 0.019）。女性（效应大小=0.75，95% CI = 0.38 - 1.13，p < 0.001）比男性（效应大小=0.13，95% CI = -0.05至0.31，p = 0.158）更容易受到利尿作用的影响（ Cochr an's Q，p = 0.003）。
咖啡因具有轻微的利尿作用，但运动可抵消这一作用。对于与咖啡因摄入相关的不必要液体流失的担忧是没有必要的，尤其是在运动前摄入时。
