Caffeine is a natural stimulant most commonly found in tea, coffee, and cacao plants. Approximately 90 percent of all adults in the world consume caffeine daily . Caffeine's main effect on the human body is stimulating the brain to make one feel more energized and alert. Adenosine, a neurotransmitter that makes the human body feel tired, builds up as humans use energy throughout the day, which makes humans feel more tired as the day progresses. Consuming caffeine will intercept the effects of adenosine on one's body, making one feel more energized. However, the human body does not metabolize and absorb all the caffeine ingested, as it is excreted by the body through bodily fluids and flushed into wastewater, which is filtered and recycled back into the environment .