Because of its stimulant effects on the nervous system, which increase our cognitive performance, caffeine is a common ingredient in drinks such as coffee, sodas and energy drinks. Despite its ability to help us stay more alert and to improve our focus, it's been thought that caffeine can have a diuretic effect and increase the risk of dehydration. However, recent studies, such as Dr. Ann Grandjean's findings that were published in the "Journal of the American College of Nutrition" in 2000, contradict the popular notion and have found that even daily caffeine consumption has no significant effects on dehydration.
Diuretic Properties
Caffeine does possess diuretic properties, meaning that it increases the rate of urination. Diuretics stimulate an increase in renal glomerular filtration, meaning that fluid filters through the kidneys more quickly and the body will subsequently excrete it at a faster rate. It does this by forcing the kidneys to excrete more sodium, which directly causes an increase in water filtration. Theoretically, the more an individual urinates, the more fluid they lose from the body. According to Peak Performance, however, significant diuretic effects are only seen with extremely high consumptions of caffeine. It continues to state that any diuretic responses that do occur because of caffeine are typically highly individualistic and depend on one's personal sensitivity to caffeine's effects.
Possible Electrolyte Loss
Sodium is an electrolyte that works alongside potassium to keep the levels of fluid balanced and move the fluid throughout the body to areas that need it. Caffeine inhibits the reabsorption of sodium, forcing it to be excreted. This directly causes the water to follow the sodium through the kidneys and to be excreted. Extreme losses in sodium can cause an electrolyte imbalance and limit fluid management, such as the body's cooling system when it sweats. However, most studies, such as the one published in 2007 in "Exercise Sports and Science Review" from Dr. L.E. Armstrong at the University of Connecticut, found no significant differences in electrolyte balance from caffeine consumption.
Fluid Balance
Along with its diuretic properties and the increased loss in electrolytes, caffeine can directly affect the total balance of fluid within the body. Because of the increase in urination, the body loses more fluid than normal. Theoretically, this increase in fluid loss can directly lead to a dehydrated state. However, findings have not supported that idea. In 2000, Dr. Ann Grandjean at The Center for Human Nutrition found no differences in hydration status from caffeine consumption. In addition, Dr. Monika Neuhauser-Berthold at the Institute of Nutritional Sciences found in her 1997 study that although subjects saw an increase in urination from caffeine use, their body fluid totals remained consistent. She concluded that this finding was presumably because the amount of fluid lost was cancelled out by the increase in fluid they consumed while drinking caffeinated drinks.
References
- "Journal of the American College of Nutrition": The Effect of Caffeinated, Non-Caffeinated, Caloric and Non-Caloric Beverages on Hydration; Ann C. Grandjean et al; 2000
- "Annals of Nutrition & Metabolism"; Coffee Consumption and Total Body Water Homeostasis; Monika Neuhäuser-Berthold et al; 1997
- "Exercise Sports and Science Review"; Caffeine, fluid-electrolyte balance, temperature regulation, and exercise-heat tolerance; L.E. Armstrong et al; July 2007
- Peak Performance: Caffeine and Hydration
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