CAFFEINE
Caffeine is a bitter substance found in coffee, tea, soft drinks, chocolate, some nuts and certain medicines. It has many effects on the body's metabolism, including stimulating the central nervous system. This can make you more alert and give you a boost of energy. For most people, the amount of caffeine in two to four cups of coffee a day is not harmful. However, too much caffeine can make you restless, anxious and irritable. It may also keep you from sleeping well and cause headaches, abnormal heart rhythms or other problems. If you stop using caffeine, you could get withdrawal symptoms (Source: National Library of Medicine, 2007)
