Phenolic content in tea green tea. Catechins constitute about 25% of the dry mass of a fresh tea leaf, although total catechin content varies widely depending on species, clonal variation, growing location, season, light variation, and altitude. They are present in nearly all teas made from "Camellia sinensis", including white tea, green tea, black tea and oolong tea. Of all the catechins in tea, EGCG is the main subject of scientific study with regard to its potential health effects. 4-Hydroxybenzoic acid, 3,4-dihydroxybenzoic acid (protocatechuic acid), 3-methoxy-4-hydroxy-hippuric acid and 3-methoxy-4-hydroxybenzoic acid (vanillic acid) are the main catechins metabolites found in humans after consumption of green
Black tea point, it is referred to as being "stewed" in the UK). When the tea has brewed long enough to suit the drinker's taste, it should be strained before serving. The ISO Standard 3103 defines how to brew tea for tasting. The biggest producers of black tea in the world are: Plain black tea without sweeteners or additives contains caffeine but negligible quantities of calories or nutrients. Some flavored tea with different herbs added may have less than 1 gram of carbohydrates. Black teas from the Camellia sinensis tea plant contain polyphenols known as thearubigins and theaflavins. Meta-analyses of observational studies