Caffeine stimulates the central nervous system, reaching the bloodstream within 30 to 45 minutes after ingestion. Because caffeine is water soluble, the body quickly absorbs it through the stomach lining. Excessive consumption of caffeine can lead to nervousness, stomach upset, muscle tremors and fast heartbeat. The stimulant produces both short and long term effects on the body.
Kidney
Caffeine acts as a mild diuretic increasing urine output. The kidneys produce urine and filter out waste products from body fluids. Electrolytes such as sodium and potassium are excreted from the body through the release of urine. Diuretics cause the loss of both excess sodium and water from the body. Sodium levels in the body also have an effect on how much calcium is excreted in urine. The New York State Osteoporosis Prevention and Education Program reports that even though caffeine slightly decreases calcium absorption and increases the excretion of calcium from the body, moderate consumption does not affect bone health. However, high intake of sodium and low consumption of foods and beverages containing calcium may contribute to bone loss after menopause.
Stomach Acid
Heavy caffeine use can lead to stomach upset. Author and media spokesperson Dr. Ronald Hoffman explains that caffeine stimulates the production of gastric acids. This in turn can cause irritation to the gastrointestinal tract. Excess stomach acids are a common cause of gastritis -- irritation or inflammation in the stomach lining. Symptoms may include loss of appetite, stomach cramps, bloating, nausea, vomiting and diarrhea. Prevention includes avoiding caffeine, alcohol and foods that irritate the stomach lining.
Circulatory System
Caffeine has the effect of increasing blood pressure in some people. Drinking too much caffeine can raise blood pressure for several hours afterward. High blood pressure increases the risk of heart attack and stroke. According to Dr. Sheldon Sheps, former chair of the Division of Nephrology and Hypertension in the Department of Medicine at Mayo Clinic, caffeine may constrict blood vessels, decreasing the flow of blood. Caffeine may also cause the release of more adrenaline into the bloodstream, which increases heart rate and blood pressure. Even if you take medication to lower your blood pressure, drinking three or four cups of coffee a day may make the drug's benefits useless. If you have high blood pressure already and drink coffee regularly, you might want to eliminate the caffeine or cut back on your total consumption.
Brain
Caffeine is similar to adenosine in chemical composition. Adenosine helps to transmit nerve signals and is what causes you to feel drowsy. Caffeine, like adenosine, attaches itself to neural receptors in the brain. When this happens, caffeine blocks adenosine so that you don't feel sleepy. Because caffeine affects the central nervous system differently from adenosine, instead of experiencing a soothing effect, you feel stimulated. The stimulated feeling results from caffeine causing neurons in the brain to fire more rapidly. Too much caffeine intake can lead to anxiety, restlessness and trouble sleeping. Sudden withdrawal may cause irritability, drowsiness, nausea and headaches.
References
- Mayo Clinic; How Much Is Too Much; Mayo Clinic Staff; March 2011
- Mayo Clinic; How Does Caffeine Affect Blood Pressure; Sheldon Sheps; November 2009
- Dr. Ronald Hoffman; Ulcers; Ronald Hoffman
- eNotes: Diuretics -- Effects on the Body
- FitDay: Caffeine -- The Neurologic Effects
- University of Maryland Medical Center; Caffeine in the Diet; May 2009
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