Caffeine is a popular psychoactive stimulant that affects the central nervous system. Most people consume caffeine to ward off drowsiness and restore alertness, although it can also increase the frequency of urination in some users. In North America, caffeine is consumed daily by about 90 percent of adults, usually in coffee, soda pop and tea. Caffeine is naturally present in a variety of plants because it is toxic to some species of insects.
Biochemistry of Caffeine
The most notable effects of caffeine on people is related to the brain. Caffeine is able to quickly pass through the blood-brain barrier, where it alters neurotransmitters, or chemical messengers of the brain. Specifically, it interferes with the action of adenosine, which normally suppresses neural activity, among other functions. Consequently, caffeine intake temporarily increases brain activity, which is perceived as an increase in alertness and reduced drowsiness and fatigue. However, altering brain chemistry also affects the kidneys and bladder, leading to increased urges and rates of urinating.
Caffeine as a Diuretic
Caffeine consumption has been proven to cause changes in the kidneys known as the diuretic effect, as cited in "Fluids and Electrolytes with Clinical Application." Like other diuretics such as alcohol, caffeine increases blood flow in the kidneys while inhibiting the re-absorption of sodium and water, leading to increased production of urine and higher rates of urination. According to "Human Biochemistry and Disease," moderate to heavy use of caffeine also weakens bladder muscles, which further provokes the need to urinate. In general terms, caffeine is regarded as a mild diuretic. About 300 mg needs to be consumed before it noticeably affects urination, although body mass and hydration levels are some of the variables involved. One cup of freshly brewed coffee contains about 100 mg of caffeine, depending on bean type and strength.
Hazards of Diuretics
The increased need to urinate can be annoying and inconvenient, but there are also physiological concerns related to moderate or heavy caffeine consumption. In some users, depending on physical activity and climate, increased rates of urination leads to dehydration, muscle cramping and twitching, headaches, irritability, restlessness and reduced mental clarity. However, regular users of caffeine develop a tolerance to the diuretic effect over time, which reduces the concern of dehydration. It is important to note that the U.S. Food and Drug Administration state that caffeine is a "generally recognized as safe" substance. Despite this, pregnant women should avoid high caffeine intake as it may cause a greater increase in urination frequency.
Caffeine Sources
In addition to coffee beans and the leaves of the tea bush, other natural sources of caffeine include kola nuts, yerba mate, cacao pods and guarana berries. In fact, guarana berries contain about twice the caffeine content per gram compared to coffee beans, as cited in "Medical Herbalism." Various other products contain caffeine, such as soda pop, sports drinks, chocolate, candy and prescription drugs.
References
- "Contemporary Nutrition"; Gordon M. Wardlaw; 2010
- "Fluids and Electrolytes with Clinical Application"; Joyce LeFever Kee; 2010
- "Human Biochemistry and Disease"; Gerald Litwack; 2008
- "Textbook of Medical Physiology -- Tenth Edition"; Arthur C. Guyton et al; 2000
- "Medical Herbalism: The Science Principles and Practices of Herbal Medicine"; David Hoffmann; 2003
Member Comments