Caffeine

In small quantities, caffeine is good for you. It is a drug which occurs naturally in coffee, tea and cocoa, and is put into many soft drinks. It is a vasodilator; that is, it opens blood vessels and has a stimulant effect on the heart and brain cortex, where it improves concentration. Caffeine wakes you up and combats tiredness. It is a diuretic, increasing water passage through the kidneys. All in all, it is as miraculous in its multiple effects as aspirin. The trouble begins when it is taken in ever-larger doses, when it has a wide range of negative effects, including heart arrhythmia and palpitations, irritability, insomnia and trembling hands.