Tea and caffeine

The bitter taste of tea is from caffeine, a alkaloid found in coffee and tea that is responsible for its stimulating effects. The content in natural green tea is about half of that in coffee, and the newer the tea the higher content it contains.

At very high doses, the stimulant can causes a racing heart rate, heart palpitations, even seizures. Thus who has arteriosclerosis and high blood pressure should be cautious not to overdose. Besides, caffeine can also have serious consequences for kids. While many adults can drink as much as 300 milligrams of caffeine a day - that's several cups of strong-brewed coffee - without suffering any unpleasant side effects, the stimulant can be harder on growing bodies. While kids overdo the stimulant, they come up short on sleep. Nearly half of kids 11 to 17 years old in the United States don't get the minimum eight hours a night, according to the National Sleep Foundation. One 2003 study by neurologists at Ohio State University found that seventh-, eighth- and ninth-graders who drink a lot of caffeine are up late at night and are more tired during the day than their peers.