A new study says many young people in the United States take substances that are claimed to make people (26) sports better. The study says that about one million Americans between the ages of 12 and 17 have used these sports supplements. Those who (27) what sports supplements they used identified creatine (肌酸) as the most (28) . The body produces creatine (29) . Some famous American (30) use products with creatine to increase the (31) of their muscles. In the United States, the substance is sold (32) in candy and other foods. However, creatine has also been linked to health problems. One doctor said that the substance causes (33) pain. He said it also has been linked to muscle injury and kidney problems. A trade group for supplement makers said it believes that creatine is safe, when it is taken by someone responsible. The trade group says there is a large amount of evidence that shows creatine is helpful for healthy people. Seventy percent of the young people questioned in the study could not identify any harmful effects that might (34) using sports supplements. Yet 96 percent of them believed that people who use the supplements face the possibility of some health damage. The researchers urged American parents and teachers to (35) children about the issue. They also urged the government to take action to limit the marketing and sales of supplements to young people. A new study says many young people in the United States take substances that are claimed to make people (26) sports better. The study says that about one million Americans between the ages of 12 and 17 have used these sports supplements. Those who (27) what sports supplements they used identified creatine (肌酸) as the most (28) . The body produces creatine (29) . Some famous American (30) use products with creatine to increase the (31) of their muscles. In the United States, the substance is sold (32) in candy and other foods. However, creatine has also been linked to health problems. One doctor said that the substance causes (33) pain. He said it also has been linked to muscle injury and kidney problems. A trade group for supplement makers said it believes that creatine is safe, when it is taken by someone responsible. The trade group says there is a large amount of evidence that shows creatine is helpful for healthy people. Seventy percent of the young people questioned in the study could not identify any harmful effects that might (34) using sports supplements. Yet 96 percent of them believed that people who use the supplements face the possibility of some health damage. The researchers urged American parents and teachers to (35) children about the issue. They also urged the government to take action to limit the marketing and sales of supplements to young people.