Most people will tell you that they can't work without a cup of coffee in the morning. Research has shown that a cup of coffee does give a person slight excitement.
Legend said that Kaldi, an Ethiopian, found his goats happier while enjoying coffee plants. Curiously, he tasted the leaves and began to dance around. Whether the legend was true or not, the discovery of coffee dates back to 800 AD. Soon Arabians were roasting coffee beans. Muslims were drinking coffee to stay awake by1000 AD. A business from Venice introduced coffee to Europe in 1615. By 1696, the Dutch started growing the coffee bush in Java. By 1723 drink in the world coffee plants were introduced to the Americans. Today, coffee is the most popular drink in the world.
Caffeine is the major chemical in coffee. It blocks(阻止 ) adenosine（腺苷酸）, a chemical that makes you sleepy. People can get a pick-me-up or stimulation(刺激) from the drink. The stimulation does not last long. Caffeine poisoning（中毒）can occur（发生） if more than 400 milligrams（毫克）of caffeine is drunk in a short period, which is about four to five cups of coffee. Caffeine will also cause sleep difficulty, so it should not be drunk before bed.
Caffeine has many advantages. Studies have shown that it helps improve some skills in elderly women. Women who drank three cups of coffee daily scored higher on memory tests than women who drank one cup of coffee. According to newser. com, one cup of coffee a day protects the brain. Coffee can also help people keep away from many diseases according to webmd. com.
Large amounts of coffee can cause nervousness, worries and a fast heartbeat. However, if you mix coffee with milk, it's fine. Caffeine can be addictive(上瘾的） like any drug, The more you drink, the more you depend on it. For some people, just one cup of coffee a day is OK.
