Caffeine is a stimulant that occurs naturally in foods such as coffee, chocolate, tea and kola nuts -- although it is also an additive in some foods, medications and supplements. Caffeine is acidic and bears a bitter taste. Although caffeine is nontoxic, in large doses it may cause problems such as anxiety, sleeplessness, headaches, abnormal heart rate and irritability. Moreover, frequent use may result in withdrawal following cessation. In addition to these effects, caffeine is a natural diuretic.
Increases Blood Volume for Renal System
As a stimulant, caffeine increases the activity of the cardiovascular system, thereby increasing heart rate and blood pressure. As a result, the renal system encounters a higher volume of blood to filter, resulting in a higher waste output. Accordingly, this property of caffeine causes more frequent urination. It may also lead to irregular heart rhythms and nutrient depletion.
Hinders Resorption of Sodium and Water
Kidneys maintain homeostasis in the bloodstream by regulating the balance between sodium and water in order to ensure bodily cells are likewise balanced. Caffeine hinders the resorption of sodium and water in the kidneys. Resorption refers to uptake into the bloodstream. Subsequently, the kidneys only have the option to withdraw water or sodium to maintain balance in the bloodstream and cells. Alternatively, caffeine prevents water depletion to the extent of causing dehydration, because caffeine is most often ingested in a liquid, such as coffee or soda, that contains water.
Relaxes Bladder Muscles
The detrusor muscles in the bladder help determine capacity limits of the bladder as well as control bladder output into the urethra. Caffeine relaxes detrusor muscles, thereby causing the bladder to feel fuller more frequently. Moreover, caffeine causes the bladder to be incapable of holding larger amounts of urine, causing urgency to urinate. This indirectly compounds the diuretic effects of caffeine.