Coffee contains caffeine, a drug that occurs naturally in many plants, such as the coffee bean.
Even though caffeine is considered a drug, it is a legal substance. It speeds up your heartbeat and metabolism also, which is the reason why drinking coffee in the morning helps to wake you up. People who do not consume caffeine on a regular basis may notice that they experience trembling, headache, nervousness, and difficulty sleeping when they do have caffeine. Those trying to quit drinking coffee or cola may also notice the same symptoms but are actually experiencing withdrawal. After getting your body used to not having caffeine these symptoms should go away.