Caffeine Intake
General caffeine intake around the world is 76mg/person/day. However it is different in the other countries.
* Scandinavia: over 400mg/person/day
* North America: 240-360mg/person/day
* UK: 280mg/person/day (a lot of people can consume almost 525mg a day)
Coffee is very popular in USA but people that live in UK give the preference to tea. The researches showed that the consumption of caffeine gained popularity due to the increased usage of stimulant drinks.
Caffeine Metabolism, Half Life and Toxic Effects
Caffein is digested very quickly and it is highly concentrated in blood 60-90 minutes after the ingestion. After that it is metabolized in the liver by the cytochrome P450 enzyme system and creates there a number of metabolites and the rest is is excreted without changes in urine. Caffeine is totally cleared from the plasma plasma and urine not until 24-48 hours after ingestion of the last dose. The general half life of caffeine is 4-5 hours but due to genetic, physiological and environmental factors it can be between 2-10 hours.
The toxic effects of caffeine are abdominal pains, vomiting, seizures and decreased consciousness. Overdosing can occur because of over consumption of pills and stimulants.
Caffeine as a Stimulant
Its stimulatory effects have the impact on the heart, lungs, blood vessels, kidneys and muscles. It can lead to the improvement in performance and sometimes strength.
Addictiveness and Tolerance of Caffeine
Caffein belongs to psychoactive drugs and it may cause tolerance and the necessity to increase the amount of its intake for stimulation. Some people may have also the withdrawal symptoms such as headaches and fatigue which can last from two days to a week. It is known that caffeine may have some criteria for dependence. But there are debates between scientists whether it can cause addiction.
The Influence of Caffeine on the Athletic Performance
The studies show that caffeine can increase the short term intense workout, 'stop-start' activities (football, rugby, etc), running on the long distance. It enhances the gym performance which helps you train more efficiently and increase the muscle mass and strength.
 However the mechanism of its ergogenic effects has not been discovered yet. It also assists in burning your fat by eliminating the carbohydrate stores which is very crucial for the athletic performance. There is a thought that caffeine is slightly fat oxidising which is useful for losing fat.
Caffein has the ability to stimulate neural signals between the brain and neuromuscular junction (it is the principal how nerves make muscles contract) and extend metabolites production in muscle due to which contraction occurs.
Some time ago the usage of caffeine was restricted by the International Olympic Committee (IOC) before the competition and blood levels should not have more than 12mcg/ml. Such restriction was made because of its ergogenic effects on performance.They thought that it can give the unfair benefits. But it was allowed during training and there was no casual drug testing for it. Since January 2004, though, any restriction on caffeine's use pre-competition has been made, because it has become widely used and socially acceptable, so caffeine-containing ergogenic aids can be taken freely during this year's Olympic events.
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