What is caffeine? Everyone is fond of their early morning drink. It may be coffee, tea, or perhaps cocoa for children. There is one ingredient common to all these substances. It is caffeine. Caffeine is found to naturally occur in about 60 plants. It may be present in the leaves, fruit or beans of the plant. In plants it acts as a natural pesticide and protects the plant from pest attacks. However, for many centuries it has been used by humans as a stimulating drink. Humans get caffeine mostly from coffee beans, tea leaves, and from cacao, kola nuts, guarana berries or yerba mate as well. Beverages such as coffee, tea, soft drinks and energy drinks contain caffeine. While humans have chewed leaves and bark containing caffeine since the Stone ages, today it is found in coffee, tea and cold drinks. In humans, caffeine stimulates the central nervous system. So it is used to increase alertness when you are tired or sleepy. Roasted coffee beans are the world's primary source of caffeine, while tea and cocoa do not contain as much caffeine. Of course, the amount of caffeine also depends on how the drink is made. Tyically one cup of coffee has about 100 milligrams (mg) of caffeine apart from small amounts of theophylline but no theobromine. Tea usually contains about half as much caffeine per serving as coffee, depending on the strength of the brew. It also contains small amounts of theobromine and slightly higher levels of theophylline than coffee. Like caffeine, theobromine also fights fatigue. Caffeine is also a common ingredient of soft drinks such as colas, that were originally prepared from kola nuts. Soft drinks typically contain about 10 to 50 milligrams of caffeine per serving. By contrast, energy drinks such as Red Bull contain as much as 80 milligrams of caffeine per serving, almost as much as a cup of coffee. The caffeine in these drinks either comes in the ingredients used or it may have been added as well. For instance, guarana, a prime ingredient of energy drinks, contains large amounts of caffeine with small amounts of theobromine and theophylline naturally. Chocolate derived from cocoa contains a small amount of caffeine, theobromine and theophylline. The amount is too small to have significant effect. The German chemist Friedrich Ferdinand Runge isolated relatively pure caffeine for the first time in the year 1819. In 1927, Oudry isolated "theine" from tea, but it was later shown theine was the same as caffeine. The chemical structure of caffeine was found out near the end of the 19th century by Hermann Emil Fischer who was also the first to achieve its total synthesis. This was part of the work for which Fischer was awarded the Nobel Prize in 1902. How does caffeine work? Caffeine is metabolized in the liver into paraxanthine (84%), theobromine (12%), and theophylline (4%). Paraxanthine (para-xanthine) increases glycerol and free fatty acids in the blood. Theobromine dilates blood vessels. Theophylline has the effect of relaxing smooth muscles of the bronchi in the lungs. Caffeine is completely absorbed by the stomach and small intestine within 45 minutes of ingestion. After ingestion it is distributed throughout all tissues of the body and is eliminated after a few hours (longer in children). The caffeine content of select common foods is shown in the table. Remember we are only talking about the caffeine content. There is no indication of the other contents such as fats and sugar, nor the calorie content. Product Serving size Caffeine per serving (mg) Coffee, brewed 207 mL 80-135 Coffee, drip 207 mL 115-175 Coffee, decaffeinated 207 mL 5 Coffee, espresso 44-60 mL 100 Tea, leaf or bag 177 mL 50 Soft drink, Fanta 355 mL 0 Soft drink, Sprite 355 mL 0 Soft drink, Coca-Cola Classic 250 mL 24 Soft drink, Mountain Dew 250 mL 38 Soft drink, Red Bull 250 mL 80 Chocolate, Cadbury's Dairy Milk 50 g 9 Chocolate, Milk (Hershey Bar) 50 g 11 Chocolate Dark (Hershey's Special Dark) 50 g 36 Caffeine makes pain relievers 40% more effective in relieving headaches and helps the body absorb headache medications more quickly, bringing faster relief. For this reason, many common headache drugs include caffeine in their formula. However, caffeine tolerance develops very quickly, especially among heavy coffee and energy drink consumers. In large amounts, and especially over extended periods of time, caffeine can lead to a condition known as caffeinism. This dependence on caffeine shows up with a wide range of unpleasant physical and mental conditions. These include nervousness, irritability, anxiety, tremulousness, muscle twitching, insomnia, headaches, and heart palpitations. Because caffeine increases the production of stomach acid, high usage over time can lead to peptic ulcers as well. Two infrequently diagnosed caffeine-induced disorders are caffeine-induced sleep disorder and caffeine-induced anxiety disorder, which can result from long-term excessive caffeine intake. Caffeine has a significant effect on spiders, which is reflected in their web construction. An array of studies has found that caffeine induces certain changes in memory and learning. However, it is still not definitely clear whether the effect is negative or positive. Meanwhile, a large part of the world still wakes up to a morning dose of caffeine!