Caffeine is a natural chemical with stimulant effects. It is found in coffee, tea, cola, cocoa, guarana, yerba mate, and over 60 other products.

Guarana (Paullinia cupana) is a plant native to the Amazon. It is a common ingredient of energy drinks and can be unsafe in large amounts.

Ginseng is an herb that has been used for various health purposes. It's a plant that grows in Korea, China, and Siberia. It's considered an adaptogen, which are natural substances that are believed to stimulate the body's resistance to stressors.

Caffeine works by stimulating the central nervous system, heart, muscles, and the centers that control blood pressure. Caffeine can raise blood pressure, but might not have this effect in people who use it all the time. Caffeine can also act like a "water pill" that increases urine flow.

Guarana contains caffeine. Caffeine works by stimulating the central nervous system, heart, and muscles. Guarana also contains theophylline and theobromine, which are chemicals similar to caffeine.

Ginseng contains many active chemicals. The most important are called ginsenosides or panaxosides. Ginseng is taken by mouth for memory and thinking skills, Alzheimer disease, depression, and many other conditions.

People most commonly use caffeine for mental alertness, headache, migraine, athletic performance, memory, and obesity. It is also used for asthma, gallbladder disease, ADHD, low blood pressure, depression, and many other conditions.

People take guarana by mouth for obesity, athletic performance, mental performance, to increase energy, and for many other reasons.