When you drink tea, coffee or soda pop, these drinks contain caffeine, which is absorbed by the stomach in as little as 45 minutes after you drink it. Then it travels to all parts of the body, so it is not just your stomach that feels the effects of caffeine. Caffeine affects people in different ways. Some people say that they cannot have any drinks containing caffeine in the evening because they will find it hard to get to sleep. Others say that having a cup of coffee or tea just before bedtime helps them to fall asleep easily.

The amount of caffeine needed to have an effect on the body varies from one person to another. It depends on the person's body size and the degree of tolerance a person has for caffeine. Even though it doesn't take long for caffeine, a mild dose will wear off in about three hours. Caffeine is seen as an ergogenic because it increases the amount of energy one has for work, whether it is mental or physical. In studies done on long distance runners, the results showed that those who consumed caffeine drinks were able to sustain the run much longer than those who drank only water or juices.

Caffeine acts as a mild stimulant on the nervous and cardiovascular systems. It decreases fatigue and increases attentiveness, allowing a person to focus on a job better even when feeling tired. Some of the other effects that caffeine has on the body include an increase in heart rate, a rise in the body's metabolic rate increased blood flow and increased respiratory rate.

When you consume drinks containing caffeine for a long period of time, your body will develop a tolerance for it. This means that in order to achieve the same effect, you will have to consume larger doses of caffeine. Many people become addicted to it and cannot go for any length of time without a cup of coffee or a soft drink. When you go without caffeine for a long period of time, the result could be headache, fatigue, irritability, depression and a lack of concentration.

The amount of caffeine in coffee depends on the type of bean used in the brew. Because of the growing addiction to caffeine, there are many flavors of decaffeinated coffee on the market and soft drinks that do not contain ant caffeine. Numerous prescription drugs also contain caffeine, especially painkillers, because it increases the ability of prescribed drug to perform in the way that it should.

In studies done on caffeine consumption, results have shown that consuming moderate amounts does not have any adverse affect on the cardiovascular system. It appears to increase the excretion of calcium, which the bones need to be strong and healthy. This is very important in the prevention of osteoporosis in older people. Research has also shown there is no link between consuming caffeine and cancer, but consuming excessive amounts of caffeine has been related to miscarriages and some birth defects.