Coffee is a brewed beverage with a distinct aroma and flavor, prepared from the roasted seeds of the Coffea plant. The seeds are found in coffee "cherries", which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia, India and Africa. Green (unroasted) coffee is one of the most traded agricultural commodities in the world. Coffee is slightly acidic (pH 5.0–5.1) and can have a stimulating effect on humans because of its caffeine content. It is one of the most consumed drinks in the world.
Wild coffee's energizing effect was likely first discovered in the northeast region of Ethiopia. Coffee cultivation first took place in southern Arabia; the earliest credible evidence of coffee-drinking appears in the middle of the 15th century in the Sufi shrines of Yemen.
In East Africa and Yemen, coffee was used in native religious ceremonies that were in competition with the Christian Church. As a result, the Ethiopian Church banned its secular consumption until the reign of Emperor Menelik II of Ethiopia. The beverage was also banned in Ottoman Turkey during the 17th century for political reasons and was associated with rebellious political activities in Europe.
Coffee berries, which contain the coffee seeds, are produced by several species of small evergreen bush of the genus Coffea. The two most commonly grown are also the most highly regarded Coffea arabica, and the "robusta" form of the hardier Coffea canephora. The latter is resistant to the devastating coffee leaf rust (Hemileia vastatrix). Once ripe, coffee berries are picked, processed, and dried. The seeds are then roasted to varying degrees, depending on the desired flavor, before being ground and brewed to create coffee. Coffee can be prepared and presented in a variety of ways.
An important export commodity, coffee was the top agricultural export for twelve countries in 2004, and it was the world's seventh-largest legal agricultural export by value in 2005. Some controversy is associated with coffee cultivation and its impact on the environment. Consequently, organic coffee is an expanding market.
Many studies have examined the health effects of coffee, and whether the overall effects of coffee consumption are positive or negative has been widely disputed. The majority of recent research suggests that moderate coffee consumption is benign or mildly beneficial in healthy adults. However, coffee can worsen the symptoms of some conditions, largely due to the caffeine and diterpenes it contains.