Caffeine's effects on the body

DAYTON, Ohio — Experts aren't in agreement when it comes to the safety of caffeine or its impact on health and/or exercise performance.

This is most likely due to the fact that individual differences make it impossible to determine who might benefit from its use and who may experience negative side effects, and to what degree. Studies have shown that caffeine increases the force and beat of the heart, increases breathing and stress hormones and temporarily elevates blood pressure.

Those who believe caffeine is safe argue that problems occur only in those who are hypersensitive or unaccustomed to it, or who consume extremely large amounts. The majority of scientific evidence seems to show that for many healthy adults, ingesting moderate quantities (250-350 mgs per day) poses no significant health risks.

A link between consuming higher amounts and certain heart problems such as arrhythmias has been reported, however. Extremely high intake (150 milligrams per 2.2 pounds of body weight) can create an "overdose" effect, which is dangerous and in rare cases, fatal. To those who are at risk, even moderate intake can create symptoms of "overdose."

Initial caffeine overdose symptoms can include flushed face, frequent urination, shakiness, rapid heartbeat, upset stomach and sleep disturbances. More severe cases can include symptoms such as acute mental confusion and visual disturbances.

Caffeine does interact with certain medications, and can also interfere with iron absorption. It can interfere with sleep quality, increases urine production, increases amounts of fatty acids in the blood, and increases production of stomach acid.

It is also a diuretic, meaning it causes water loss from the body. Drinking a cup of water for each cup of caffeinated beverage you consume can help offset this loss. If you are pregnant, anemic, have digestive or heart problems, or other medical conditions, ask your doctor for appropriate guidelines concerning use of caffeine.

Caffeine is metabolized and expelled by the body, so it does not get stored or accumulate in the bloodstream. It is absorbed quickly from the stomach and peaks in the bloodstream in about 1-2 hours. For the average person consuming 100 mg, it takes roughly 5 to 7 hours to metabolize half of this.

Until all of the caffeine has been processed, the central nervous system continues to be stimulated.

Caffeine is classified as a drug and can produce withdrawal symptoms if usage is stopped. Looking at over 170 years of research on caffeine withdrawal, a study at Johns Hopkins University suggests that true caffeine addiction and withdrawal symptoms can occur from drinking as little as one cup of coffee per day.