An energy drink is a type of beverage containing stimulant drugs, chiefly caffeine, which is marketed as providing mental and physical stimulation. They may or may not be carbonated and many also contain sugar or other sweeteners, herbal extracts and amino acids. They are a subset of the larger group of energy products, which includes bars and gels, and distinct from sports drinks, which are advertised to enhance sports performance. There are many brands and varieties of energy drinks. Coffee, tea and other naturally caffeinated beverages are usually not considered energy drinks. Soft drinks such as cola may contain caffeine, but are also not energy drinks. Some alcoholic beverages, such as Four Loko, used to contain caffeine and other stimulants, but such drinks were banned in the United States in 2010. According to the Mayo Clinic, it is safe to have up to 400 mg of caffeine a day. This is equivalent to 4 cups of coffee or 2 energy shots.