Diuretic Effect of Caffeine
Caffeinated compounds are recognized as having diuretic action and compromises fluid balance in the body. Its diuretic effect causes people to expel more urine than the amount of water in the drink of choice. Chemically, Caffeine is a xanthine drug that increases the glomerular filtration rate. It inhibits the reabsorption of sodium compounds and therefore most of them go back to the blood and water follows them. Sodium combines with the fluid forming urine .This effect stimulates the role of the kidney resulting in diuretic effects in the body (Maughan, 2003). It also causes incontinence in some men and women with an urge to urinate even if the bladder is not yet full causing dehydration in the body.
According to Maughan (2003), a study by Loughborough University suggests that acute ingestion of caffeine in large quantities result in short-term stimulation of urine outputs. Adenosine in the kidney promotes reabsorption of sodium, conversely, large amounts of caffeine blocks the reabsorption process resulting in increased glomerular filtrate rate. Sports people and other physically active groups lose much water from their body. The rate of dehydration is accelerated by heavy intakes of caffeinated compounds by eliciting extra water secretions by the kidneys (Ming & Lautt, 2010).
Neuhauser-Berthold et al. (1997) studied the responses of twelve people and the results showed that ingestion of 642 mg of caffeine resulted in an increase in urine output of 753ml and a loss of body mass compared with a controlled trial where an equal volume of water was consumed. This study supports the argument that large intake of caffeine induces dehydration effect to active people. However, single caffeine doses have little or no diuretic action. Regular intake makes the users become habituated to its effects thus diminishing its action.
Maughan RJ, & Griffin J (2003). Caffeine ingestion and fluid balance: A review. Journal of human nutrition and dietetics: The official journal of the British Dietetic Association, 16 (6), 411-20.
Ming, Z., & Lautt, W. W. (2010). Caffeine-induced natriuresis and diuresis via blockade of hepatic adenosine-mediated sensory nerves and a hepatorenal reflex. Canadian journal of physiology and pharmacology, 88(11), 1115-1121.
Neuhauser-Berthold, B.S., Verwied, S.C. & Luhrmann, P.M. (1997) Coffee consumption and total body water homeostasis as measured by fluid balance and bioelectrical impedance analysis. Ann. Nutr. Metab.41, 29–36.