Energy drinks such as Red Bull, Monster Energy Assault and Rockstar contain about 160 milligrams of caffeine in a 16-ounce can and can pose health risks to teens, including rapid heartbeat, high blood pressure and obesity, according to report in the journal Pediatrics in Review. Daily intake of more than 100 mg of caffeine is considered unhealthy for teens, lead author Dr. Kwabena Blankson said.