 Welcome to Spotlight. I'm Liz Wade. And I'm Luke Haley. Spotlight uses a special English method of broadcasting. It is easier for people to understand, no matter where in the world they live. In 1819, a young German doctor discovered a drug. The doctor's name was Friedlieb Ferdinand Lunge. A friend had given Lunge some coffee beans to study. They were small and dark brown. As he tested the beans, he discovered a chemical inside them. Caffeine Today, caffeine is the most used drug in the world. Many people depend on caffeine to help them start the day. And more and more products contain caffeine. But there are negative results from using too much caffeine. How much is too much? Today's Spotlight is on caffeine. Caffeine is a drug that naturally exists in some foods. It is found in coffee beans, cocoa beans, guarana, yerba mate, tea, and other plants. Through history, people from all over the world have grown and used plants for the effect of caffeine. But today, people commonly get caffeine through coffee, tea, or soft drinks like Coca-Cola. In a plant, caffeine is a natural pesticide. It makes insects unable to move and then kills them. But in a person's body, caffeine acts very differently. It speeds up a person's central nervous system inside the body. It stimulates the brain. That is, it makes a brain act and react faster. Some people feel that they can be more creative when they drink caffeine. It makes people feel more awake and it can also increase physical performance in sports. Caffeine affects a person quickly. Imagine a person who is drinking a cup of coffee. The drug begins to affect him about five minutes after he starts drinking it. In 30 minutes, the caffeine affects the person most strongly. After about four and a half hours, his body has used about half the amount of caffeine. And by the next day, the caffeine is gone. Caffeine does not stay in the body. Many people begin their day with caffeine in coffee or tea. Spotlight writer Kristie Van Aragon drinks coffee every morning. But is it a good thing? She says, Coffee makes me feel more awake and it helps me concentrate. But when I forget to drink it, I get painful headaches. And when I drink too much, my hands shake and I talk really fast. Coffee is great most of the time, but it also causes some problems. These effects can be common for people who drink caffeine. In fact, people can come to depend on caffeine. People who try to stop drinking caffeine may be very tired, have muscle pains or even have stomach pain. But these symptoms usually stop in about a week. Too much caffeine can also cause problems. People who have had too much caffeine may have head pain or stomach pain. They may have a rapid heartbeat. They may feel anxious, worried or nervous. Too much caffeine can make a person unable to sleep. But there are also more serious effects when people take extremely high amounts. These effects include a feeling of not knowing where you are, body movements you cannot control or even death. In the United States and the United Kingdom, health experts have set a safe level of caffeine a person can take. They advise that people do not take more than 400 mg of caffeine in a day. That is equal to about 4 or 5 cups of coffee. Many experts believe this amount is safe for an adult. Murray Carpenter wrote a book about caffeine. He told news organization NPR. For people who are using caffeine moderately, it is probably perfectly healthy. And we know there are some signs that we may even get some good effects out of long term coffee drinking. Researchers cannot agree if caffeine is good for people or bad for them. Caffeine does have some bad effects. But like Carpenter says, caffeine also has some good effects. Research shows that drinking coffee and tea with caffeine may reduce the risks of some kinds of cancer. It can reduce a person's risk of getting type 2 diabetes. And even though it increases blood pressure and a person's heart rate, it does not seem to cause problems with a person's heart. But these good effects do not come from drinking caffeine in soft drinks. Just drinks like coffee and tea. All of this information may make a person wonder what to do. But it gets worse. That is because recently companies have been adding caffeine to more and more drinks and food. People may not know how much caffeine they are taking. The FDA is a government agency in the United States. It sets safety rules for food and drugs there. In 2013, the FDA began investigating caffeine. They were looking particularly at caffeine in energy drinks and food. Michael R. Taylor works at the FDA. He told about a new chewing gum containing caffeine. Each stick of gum contains caffeine. He explained how products like these can be harmful for young adults and children. The gum is just one more sad example of the movement to add caffeine to food. Our concern is about caffeine appearing in many new products. This includes products that may look good to children and young adults. One package of this gum is like having four cups of coffee with you. The large number of these products in the marketplace worries us. Companies are putting caffeine in products that young adults and even children may want to try. Many government organizations and health experts are working to regulate caffeine. They want to make rules about what products can contain caffeine and how much caffeine those products can use. However, it is not an easy job. Stephen Braun wrote a book about caffeine. He told the BBC. One problem with trying to regulate the substance is that it affects everyone differently. People have different bodies and different ways of processing food. It is impossible to say what a safe limit is for everyone. Ultimately, you have to be your own scientist. There is no other good method than carefully experimenting on yourself. It is important for a person to know how much caffeine he is getting through drinks and food. But it is also important for him to know how caffeine affects his body. A person should know what his body can manage. What about you? Do you use caffeine? Do you think putting caffeine in other foods and drinks is a good idea? Tell us what you think. You can leave your comments on the script page for this program. The writer of this program was Liz Wade. The producer was Luke Haley. The voices you heard were from the United States and the United Kingdom. All quotes were adapted for this program and voiced by Spotlight. You can find our programs on the internet at www.radioenglish.net. This program is called The World's Favorite Drug. We hope you can join us again for the next Spotlight program. Goodbye.