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Bad teeth, a heavier body? And now, weaker bones (骨骼). Last week, American scientists found another bad thing about cola: It's bad for our bones, especially women's bones.

Well, if cola is bad for us, you may want other popular drinks, for example, energy drinks (功能饮料). Energy drinks look cool. Their makers say they give you energy and make you better at sports. So, many students drink them before exams to help them stay awake.

But wait. To keep you awake, most energy drinks have a lot of caffeine (咖啡因). They are like a strong cup of coffee or tea. If you drink a lot of them, your heart will beat faster. You will feel nervous. You could also have sleeping problems and find it hard to live without them.

Amanda Smith is a 16-year-old US junior high school student. She drinks one or more energy drinks every day. She started to do this a year ago before dance class. But now, Smith says, "I drink them whenever I feel weak or before a test. I cannot help drinking them."