Caffeine is probably the world’s best known stimulant.
It occurs naturally in coffee beans, several types of tea and at least 60 other different plants. Besides occurring naturally, caffeine can be synthesized in a laboratory, though all forms have the same chemical composition and similar effects.
According to ancient Chinese folklore, caffeine was first discovered when the Chinese emperor Shennong accidentally discovered tea by boiling certain leaves in water. The result was a “fragrant and restorative drink” (1). Coffee is believed to have first been drunk in the middle east during the fifteenth century, and it soon spread throughout the world as a popular energy-boosting beverage. Caffeine as an individual chemical compound was first isolated in 19th century France (2).
Caffeine is currently the most widely consumed psychoactive compound in the world. A powerful stimulant, it is used to promote wakefulness as well as to enhance mental mental simulation and physical performance (3). Research suggests that steady caffeine use may provide long-term health benefits including reducing the risk of Alzheimer’s Disease, cirrhosis and liver cancer (4, 5).
Caffeine is absorbed through the intestines and acts upon adenosinergic pathways in the central nervous system (6). In normal conditions, adenosine causes relaxation and sedation, but caffeine interacts with adenosine receptors and prevents this action (7). Optimal doses of caffeine range widely between 100mg and 500mg, the exact amount determine by weight, individual sensitivity, and habituation (8). Steady caffeine use can result in tolerance, thus requiring higher doses to achieve the desired effect. Depending on the delivery method, caffeine reaches its peak of effect between 15 minutes and 2 hours after ingestion (9).
Caffeine is effective by itself, thought it is often combined with other ingredients. As mentioned above it is often used as a stimulant for mental alertness, energy and focus, as a performance-enhancer for vigorous exercise, and is also used to support fat-burning (10, 11, 12). Caffeine is often combined with theanine to increase a range of cognative functions. Other ingredients like milk thistle, curcumin and quercetin work well with caffeine as they increase caffeine levels in the bloodstream (13, 14).