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The Effects of Caffeine on Urine

author image Naomi Parks
Naomi Parks has been a freelancing professional since 2004. She is a biochemist and professional medical writer with areas of interest in pulmonology, pharmaceuticals, communicable diseases, green living and animals. She received her Bachelor of Arts in biological anthropology from San Francisco University and her Master of Science in biochemistry from Pace University.
The Effects of Caffeine on Urine
Caffeine is a diuretic, meaning that it increases your urine output. Photo Credit: chayathon2000

Caffeine is a chemical primarily found in coffee and tea, but which also appears in various sodas, sports drinks and foods. It is a stimulant, therefore causing changes in metabolism as well as increases in focus and energy. Caffeine is addictive and can cause withdrawal following cessation after frequent use. In addition, caffeine can cause alterations in urine.

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Diuretic Effects

Caffeine is classified as a diuretic, which means that it increases urine output. The primary reason why caffeine increases urination is that it increases golmerular blood pressure, or blood pressure within capillaries in kidneys. This, in turn, increases blood filtration, resulting in an increase in urine.

Water Concentration

Another reason why caffeine is a diuretic is that it prevents sodium ion resorption--or, increase in sodium ion blood serum levels--which increases urination, but decreases water filtration. This is because water filters from the blood through the kidney and into the bladder during sodium ion resorption. Given that caffeine prevents the resorption process, water filtration is likewise inhibited.

Color and Scent

Because the prevention of sodium ion resorption reduces water filtration from the blood while increasing urination, caffeine indirectly causes urine to become more concentrated with urea, ammonia and other wastes. As a result, caffeine can cause urine to become darker in color and pungent. This is also a classic indication of dehydration, but given that caffeine prevents water filtration from the blood, it is almost impossible to become dehydrated as a result of caffeine consumption.

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  • "Human Biology, Fifth Edition"; Danial D. Chiras; 2005
  • "Nutrition, Volume 1"; Paul M. Insel, Elaine R. Turner and Don Ross; 2004
  • "Nicotine, Caffeine and Social Drinking: Behaviour and Function"; Jan Snel and Monicque M. Lorist; 1998
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