Short Term Effects of Caffeine

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Many people are drawn to the effects of caffeine delivered in coffee, tea, soft drinks and supplements. Though people's responses to caffeine vary, it is generally considered a mild stimulant. According to, most people can consume 200 to 300 milligrams -- the amount found in two to four cups -- daily without harm. Caffeine in any amount can cause positive and negative short-term effects. For specified guidance, discuss potential risks and benefits of caffeine with your doctor.

Increased Blood Pressure

Caffeine can cause an immediate blood pressure increase. In some cases, such increases are dramatic. According to Harvard School of Public Health, if you are not a regular coffee drinker and you begin drinking coffee, you will experience a substantial raise in your blood pressure. If you continue to drink it, however, your blood pressure will level off. Such raises are temporary, but can potentially dramatic. People who consume coffee or other caffeinated beverages regularly may develop a tolerance and experience fewer blood pressure symptoms as a result. A report from Columbia University explains that if you already have high blood pressure you, caffeine intake will cause further increases in blood pressure, which may pose negative health consequences.

Improved Athletic Performance

Caffeine has the potential to improve athletic performance in some people. According to research published in "Medicine & Science in Sports and Exercise" in October 2008, cyclists who ingested 100 milligrams of caffeine, the amount in one to two cups of coffee, performed markedly faster than cyclists who consumed a placebo prior to exercise. The cyclists who consumed the caffeine also exhibited improved cognitive function during exercise than their counterparts. Researchers deduced that modest amounts of caffeine may prove helpful for athletes who partake in activities that require exercise combined with mental concentration. Since people react differently to caffeine, this effect varies among individuals.

Diuretic Effect

Diuretics are substances that flush fluids from the body. Though caffeine is not the powerful diuretic or precursor to dehydration it was once thought to be, it can cause mild diuretic effects. According to a study published in "Medicine and Science in Sports and Exercise" in January 2009, caffeine can increase urine volume and sweat in people when consumed just prior to exercise. For this reason, some people avoid caffeine for fear that the need to urinate may hinder their exercise routine. As long as a person has access to a restroom, modest caffeine consumption is unlikely to pose problems regarding fluid loss. Excessive caffeine, however, may cause heightened effects, including frequent or intense need to urinate and resultant dehydration.