Caffeine occurs naturally in more than 60 plants including coffee beans, tea leaves, kola nuts used to flavor soft drink colas, and cacao pods used to make chocolate products. Man-made caffeine is sometimes added to foods, drinks, and medicines. Ninety percent of people in the world use caffeine in one form or another. In the U.S., 80 percent of adults consume caffeine every day – the average adult has an intake of 200 mg per day, the amount in two 5-ounce cups of coffee or four sodas. A study of 7th, 8th, and 9th grade students in Ohio found that students took in an average of 53 mg of caffeine per day, but almost one in five students took in more than 100 mg of caffeine each day.