The most common sources of caffeine for human consumption are the tea leaves of the Camellia sinensis plant and the coffee bean, the seed of the Coffea plant. Some people drink beverages containing caffeine to relieve or prevent drowsiness and to improve cognitive performance.

Feb 21, 2025 · Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks. Keep in mind that the actual caffeine content in beverages varies widely, especially among energy drinks.

May 18, 2023 · Caffeine is a natural stimulant consumed throughout the world. This article reviews caffeine and its health effects, both good and bad.

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

Mar 21, 2025 · What is caffeine? Caffeine is a type of drug called a stimulant, meaning it increases chemicals in your brain called neurotransmitters.

Jun 26, 2025 · Caffeine is present in ground coffee in amounts ranging between 0.75 and 1.5 percent by weight. The average cup of coffee thus contains about 100 mg (0.003 ounce) of caffeine. The caffeine content of tea varies greatly depending on the strength of the tea, but it averages about 40 mg.

Although we tend to associate caffeine most often with coffee or tea, the research below focuses mainly on the health effects of caffeine itself. Visit our features on coffee, tea, and energy drinks for more health information related to those beverages.

Jul 24, 2023 · This article will look at the potential health benefits and risks of caffeine, the questions of energy drinks, and the likelihood of a caffeine overdose occurring.

Sep 8, 2021 · Many people enjoy a cup of coffee or tea to give them a boost. But is it safe? Learn more about caffeine.

Jul 14, 2025 · Is caffeine good or bad for you? Learn how it affects sleep, IBS, anxiety, focus, and fatigue—and how to personalize your intake for optimal health.