The Reactions of Caffeine

When you consume caffeine, your body has many physical reactions. The intensity of these reactions varies depending on a number of factors, including your age, gender, weight, metabolism, medical condition, amount of caffeine consumed, caffeine consumption habits and other biological factors. Generally speaking, an amount less than 200 mg a day is unlikely to produce any adverse reactions, but an amount greater than 500 mg a day may greatly increase your risk of experiencing unpleasant side effects. Although the caffeine content of food and drinks can vary considerably, an average cup of coffee contains about 100 mg of caffeine, an average cup of caffeinated tea contains about 50 mg, and an average caffeinated soft drink contains about 30 to 40 mg, according to the Center for Science in the Public Interest. If you are concerned about the way your body reacts to caffeine, contact your doctor.

Central Nervous System

The functions of your central nervous system speed up after you consume caffeine. This provides a temporary boost of alertness and energy, and might improve cognitive performance. However, caffeine increases your heart rate and may increase your risk of coronary heart disease, although the research is inconclusive. Caffeine may cause you to urinate more frequently than usual. You also may experience nausea, muscle tremors, gastrointestinal problems or headaches due to this stimulation of the central nervous system.

Emotions

Caffeine may alter your emotional state or mood. People who are used to consuming caffeine on a regular basis may experience an improvement in their mood after consuming caffeine, according to a study published in the 2005 issue of "Psychopharmacology." However, amounts larger than 500 mg have been known to cause irritability, anxiety, tension and restlessness, according to the Mayo Clinic website.

Sleep

Caffeine may have a negative effect on your sleep. Caffeine blocks adenosine receptors, which prevents you from feeling tired. While this function is desirable if you need to increase alertness or stay awake, it can be detrimental if you are trying to get a good night's rest. Even if you can fall asleep after consuming caffeine, you might not sleep as deeply as you usually do, according to the American Academy of Sleep.

Considerations

If you consume caffeine frequently, you might develop a physical tolerance to it so that you need increasingly larger amounts of caffeine in order to feel the same physical effects. If you stop consuming caffeine, you might experience withdrawal symptoms such as muscle aches, depression, irritability, fatigue and headaches. Caffeine withdrawal symptoms typically go away within a few days, but taking a pain reliever or getting extra rest may help you feel better in the meantime.