Caffeine is a common substance found in many different foods and drinks, including coffee tea, energy drinks, soft drinks and chocolate. Caffeine is a stimulant and as such has direct effects on the central nervous system, including increasing heart rate and blood pressure which can speed up metabolism. In many cases, caffeine has negative side effects such as agitation, anxiousness and sleep disturbance. Many supplements and weight loss plans include caffeine.
Nervous System Effects
Caffeine stimulates the central nervous system by increasing heart rate and blood pressure. Caffeine works as an antagonist to adenosine, a nucleoside consisting of a sugar and the amino acid adenine, which causes dilation of blood vessels. It blocks the effects of adenosine, causing constriction of the blood vessels and therefore increasing blood pressure. As heart rate speeds up, the pressure inside the arteries increases as well. Oxygen transport to the muscles increases with heart rate, causing an increase in metabolic activity and thus an increased metabolism. People with pulmonary or heart disorders can be especially sensitive to the effects of caffeine and should consult their physician prior to consumption in any form.
Benefits
When used as stimulant, caffeine can increase alertness, allowing you to focus more clearly. Many people drink coffee in the morning to wake up. When adenosine is blocked, adrenaline is released, causing many of the previously mentioned effects. Adrenaline gives the muscles a boost and increases energy to sustain longer exercise sessions before fatigue sets in. Dopamine, a neurotransmitter associated with good feelings, also is released as a result of caffeine ingestion. The positive effects of caffeine have been well established. The International Olympic Committee has placed a ban on athletes whose urinary caffeine concentrations exceed a limit equal to 12 mg/ml.
Negative Effects
Increased heart rate can be a benefit of caffeine when used as a supplement to exercise, but people without previous knowledge of the actions of a stimulant may be surprised and may even feel palpitations from caffeine use. Increased blood pressure is usually a negative thing, especially in individuals with history of high blood pressure. Anxiety, agitation and sleeplessness can also happen as a result of caffeine consumption. Without sleep the body becomes less efficient at repairing itself and may cause drowsiness in the morning, thus leading to increased caffeine intake, perpetuating the cycle. According to a recent study in "Stoke: Journal of the American Heart Association," caffeine consumption was the leading trigger causing rupture of a brain aneurysm, leading to stroke.
Considerations
Caffeine, like any stimulant, can be abused, leading to addiction. Though it may seem harmless to the apparently healthy adult, caffeine is a drug and alters the body's normal physiologic processes. According to the Caffeine Awareness Association, 29 childhood deaths between 1989 and 2005 were attributed to caffeine. Always consult your physician prior to any caffeine consumption, and check with your doctor should any unwanted side effects occur. Pregnant and nursing women especially should talk to their doctors before any use of caffeine.
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