Friday, August 1, 2008

· Temporarily enhances mental alertness and concentration.
· Can improve athletic performance by temporarily increasing endurance.
· May abort an asthma attack by relaxing constricted bronchial muscles.
1.Is mildly addictive and can result in withdrawal symptoms.
2.Can cause amounts can produce tremors, palpitations, and feelings of anxiety.
3.Diuretic effect increases urination.
4. Lowers the body’s absorption of calcium by increasing the amount lost in urine and stools.
5. Can increase blood pressure.

By far our most popular (and least harmful) addictive drug, caffeine is the stimulant in coffee, tea, chocolate, and soft drinks; it is also added to some painkillers, cold medications, weight-loss supplements, and drugs used to promote mental alertness. Within a few minutes after caffeine is ingested, it is absorbed from the small intestine into the bloodstream and carried to all the body’s organs. It speeds the heart rate, stimulates the central nervous system, increases the flow of urine and the production of digestive acids, and relaxes smooth muscles, such as those that control the blood vessels and the airways.
Although caffeine in moderation is generally harmless, sudden withdrawal can often cause headaches, irritability, and other symptoms that vary in severity from one person to another. For example, in some people who are sensitive to caffeine, the substance can trigger migraine headaches, while in others it might actually abort a migraine by relaxing the constricted blood vessels that are causing the throbbing head pain. People with some types of heart-valve disease are very often advised to forgo caffeine altogether because it can provoke heart palpitations or other cardiac arrhythmias.
The stimulant in caffeine enhances mental performance by increasing alertness and the ability to concentrate. For many people a cup of coffee helps them "get going" in the morning, and coffee or tea breaks during the day give them a boost when energy lags.
Athletes have long observed that one or two caffeine drinks an hour before competition can improve performance, especially in endurance sports like distance running. Studies confirm that 250 mg of caffeine-the amount in two cups of strong coffee-increases endurance, presumably because caffeine increases the body’s ability to burn fat for fuel. However, while high doses may improve performance, they can also cause side effects and any athlete must be aware of his individual tolerance.
Ingestion of caffeine late in the day can result in a sleepless night, and excessive intake can lead to caffeinism, a syndrome marked by insomnia, feelings of anxiety and irritability, rapid heart-beat, tremors, and excessive urination. These symptoms abate with the gradual withdrawal of caffeine. Otherwise, caffeine is relatively non-toxic; a fatal adult dose of the stimulant would require rapidly consuming the amount found in 80 to 100 cups of coffee.
Because caffeine, especially that in coffee, increases the production of stomach acid, ulcer patients are often advised to limit coffee (including decaffeinated) consumption to one cup after a meal. Many ulcer patients can tolerate tea, however.

Because caffeine, especially that in coffee, increases the production of stomach acid, ulcer patients are often advised to limit coffee (including decaffeinated) consumption to one cup after a meal. Many ulcer patients can tolerate tea, however.
Caffeine can prompt a modest temporary rise in blood pressure; it also speeds up the heart rate. There’s no need for most heart patients to eliminate coffee or tea from their diets, but they should use it in moderation-cardiologists generally advise no more than 400 to 450 mg of caffeine per day. Older people with hypertension may be more sensitive to caffeine and should limit their intake to one cup per day.
The safety of caffeine consumption during pregnancy is controversial. Some studies suggest that drinking one or two cups of coffee each day is associated with a very small increase in risk of miscarriage and low-birth-weight babies but others do not. There is stronger evidence that drinking large amounts of caffeine daily during pregnancy may increase risk of a miscarriage, preterm delivery or having a low-birth-weight baby. Some experts suggest that women avoid coffee during pregnancy while others recommend that pregnant women limit their daily caffeine consumption to about 150 mg-the amount found in one-and-a half cups of coffee-spread over the entire day. Because caffeine enters breast milk, nursing mothers should either skip caffeinated beverages altogether or consume them at least 3 hours before breast-feeding.
Caffeine reduces calcium absorption, which can increase the risk of osteoporosis, especially in older women. Those who are heavy coffee drinkers should either consume more milk, low-fat yogurt, and other high-calcium foods or consider taking calcium supplements.
Some people prefer decaffeinated coffee but worry that the decaffeination process introduces some undesirable substances into the coffee. While the process may be harmful to the flavor of the coffee, it is not harmful to its drinker. Basically green coffee beans are soaked in water to extract the caffeine. This solution is then treated with a solvent in which caffeine is highly soluble. The solvents that are used never come into contact with the beans themselves and in any case are readily removed.

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