| 连续11天服用咖啡因对照实验中，水潴留的体液电解质及肾的指标
供稿：运动机能学，营养学，生理学和神经生物学，康尼提格大学
主要内容：本研究的目的是确定三个剂量的咖啡因对照实验中对体液电解质平衡和肾功能的影响。在1-6天（平衡期）共59人（男性，21.6±3.3岁）每天每公斤体重服用3mg咖啡因。7-11天（治疗期）每天每公斤体重服用三个剂量的咖啡因：0mg（G0，安慰剂组，20人），3mg（G3组，20人），6mg（G6，19人），不许另外摄入咖啡因。持续记录实验对象的食物和饮料摄入，在第1、3、6、9、11天时测量下列参数：体重、尿渗透压、尿比重、尿颜色、24小时尿量、24小时Na/K、排泄量、24小时肌苷量、血尿素氮、血清Na/K浓度、血浆渗透压、血细胞压积和血浆总蛋白。所有与水平衡有关的指标（包括尿量）在三个实验组（G0、G3和G6）之间并没有显著差异（P＞0.05）。虽然不同时间有些指标有显著差异（P＜0.05＝，意味着各组内有急性扰动，但全部水指标都处于正常临床范围内。
结论：在连续11天服用咖啡因对照实验中，在G3和G6组无水潴留的迹象。这些发现对于广泛公认的咖啡因是一种慢性利尿剂的观点提出了质疑。
Fluid-electrolyte
and renal indices of hydration during eleven days of controlled
caffeine consumption. Armstrong, LE, Pumerantz, AC, Roti,
MW, et al. July 2004. In review.
Departments of Kinesiology, Nutritional
Sciences, Physiology & Neurobiology, University of Connecticut,
Storrs, CT.
This investigation determined if 3
levels of controlled caffeine consumption affected fluid-electrolyte
balance and renal function differently. Fifty-nine active
males (mean + SD; age, 21.6 + 3.3 y) consumed 3 mg caffeine?kg-1?d-1
on days 1-6 (equilibration phase). On days 7-11 (treatment
phase), subjects consumed either 0 mg (G0; placebo; n=20),
3 mg (G3; n=20), or 6 mg (G6; n=19) caffeine?kg-1?d-1 in capsules;
no other dietary caffeine intake was allowed. Subjects maintained
detailed records of food and fluid intake. These variables
were measured on days 1, 3, 6, 9 and 11: body background="../images_new/bg_hei.jpg" mass, urine
osmolality, urine specific gravity, urine color, 24-hour urine
volume, 24-hour Na+ and K+ excretion, 24-hour creatinine,
blood urea nitrogen, serum Na+ and K+, serum osmolality, hematocrit,
and total plasma protein. No significant differences were
detected between groups G0, G3 and G6 (P>0.05) for any
of the hydration-relevant variables, including urine volume.
Although a few significant differences occurred between days
(P<.05), indicating acute within-group perturbations, all
hydration indices were within the normal clinical range. In
conclusion, no evidence of hypohydration was observed in G3
or G6 during 11 d of controlled caffeine consumption. These
findings question the widely accepted notion that caffeine
acts chronically as a diuretic.
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