Tea has evolved in many ways since it was first produced in China about 5,000 years ago. According to legend, tea was discovered accidentally by Shen Nung, a Chinese emperor who was pleasantly surprised by the flavor of his drink after tea leaves fell into his pot of boiling water. Since then, tea has turned into one of the most popular beverages on earth. With 84 billion servings of tea consumed in the U.S. in 2018, many people are turning to tea for variety and as an alternative to sugary drinks.
There are four main categories of tea: black, oolong, green and white. While they may seem very different from each other, they actually have much in common—they all come from the same evergreen plant, camellia sinensis, and they all contain caffeine. You may be wondering: If all major types of tea come from the same plant, how are the unique flavor profiles of each achieved, and how do the caffeine levels in tea compare for each type?
Black tea is the most popular tea in the U.S., with sales accounting for 84 percent of all tea consumed. Black tea originated in the Assam state of India, but it is also grown widely in other countries, including China. Black tea’s characteristic dark color is a function of a process called withering. Once the tea leaves are plucked from the plant, they are laid out to dry. The leaves lose their moisture until they reach about 55–70 percent moisture by weight. The leaves are then twisted and torn up to initiate oxidation—a process that releases enzymes responsible for the overall color and taste characteristics of the tea. Once the desired level of oxidation is achieved, the leaves are heated and dried to about three percent moisture. The heat caramelizes natural sugars and contributes to the depth of flavor in the finished tea. When black tea is steeped, it results in a deep red-brown color with a slightly astringent taste. A cup of black tea contains about 50 milligrams of caffeine per eight-fluid-ounce serving, roughly half the amount in a typical cup of coffee.
Oolong tea is commonly produced in southern China and Taiwan. Similar to black tea, oolong tea leaves are withered after harvesting, then rolled and oxidized, but for only about half the time of black tea. The semi-oxidized leaves are dried, and the resulting tea resembles the body of a black tea but with a pale or yellow color that matches the brightness of a green tea. A cup of oolong tea contains slightly lower caffeine levels than those of black tea, at about 38 mg per 8 fl oz serving.
Green tea is the second most popular tea in the U.S., accounting for 15 percent of total tea consumed as of 2018. Green tea gets its name because the leaves are not oxidized and they maintain their original green color. After being plucked, the leaves are steamed, rolled, then dried to stop the oxidation process. Once the leaves contain about three to four percent moisture, they are then crushed into small pieces or ground into powder. Since oxidation doesn’t occur, green tea has a subtler flavor than black or oolong tea with about half the amount of caffeine (25 mg per 8 fl oz cup).
The least processed of the four major teas is white tea. Unlike other teas, white tea leaves are harvested during the budding process when the leaves are immature. They’re then withered to achieve a moisture content of about five percent. For white teas, the rolling and oxidation process is skipped. The finished tea isn’t actually white, but pale yellow in color. The flavor produced is lighter than black and green teas, and the caffeine content is the lowest of the four teas—at about at 15 mg per 8 oz cup.
Other Herbal Teas
It is important to note that there are many “herbal” teas that do not contain caffeine, such as mint or rooibos. They come from a variety of plants, but not from camellia sinensis. It is easy to confuse them with caffeinated tea since they are both often referred to simply as “tea.” Both are delicious—but only black, oolong, green and white tea will give you a caffeinated pick-me-up.
As trends towards wellness, variety and sustainability continue to grow, so will innovation in tea. Be sure to check labels to understand how much caffeine is in the tea products you enjoy.