Differences between green and black tea include their hue, caffeine levels, antioxidant profiles and method of processing. Both green and black tea come from the same plant, but the processing methods give each type a different color and oxidation level.
After being harvested and withered, tea leaves are either crushed, torn and rolled to allow oxidation or heated to halt oxidation. Oxidized leaves become black tea, while unoxidized leaves become green tea. Oxidation creates a darker-hued tea and results in a stronger taste. While black and green are the most common classifications, there are actually thousands of types of tea. White tea undergoes less oxidation than green tea, while oolong tea is processed and oxidized to a level between green and black tea.
Black tea typically has more caffeine than green tea on average, but some stronger green teas can have more caffeine than weaker black teas. The specific processing method and the age of the tea leaves affect the caffeine content. Steeping time and whether the tea is loose or in tea bags can also affect how much caffeine is in a cup of prepared tea.
Green teas are typically higher in antioxidants called catechins, while black teas are higher in theaflavins and thearubigins. However, all teas contain a combination of these compounds, which may help protect tea drinkers from cancer and cardiovascular disease.