Black tea remains inconclusive. Black tea Black tea is a type of tea that is more oxidized than oolong, green, and white teas. Black tea is generally stronger in flavour than the less oxidized teas. All four types are made from leaves of the shrub (or small tree) "Camellia sinensis." Two principal varieties of the species are used – the small-leaved Chinese variety plant ("C. sinensis" var. "sinensis"), used for most other types of teas, and the large-leaved Assamese plant ("C. sinensis" var. "assamica"), which was traditionally mainly used for black tea, although in recent years some green and white teas have
Camellia sinensis there is no high-quality evidence that tea confers significant benefits. In clinical research over the early 21st century, tea has been studied extensively for its potential to lower the risk of human diseases, but none of this research is conclusive as of 2017. Caffeine is a molecule produced in "Camellia sinensis" and functions as a secondary metabolite. Caffeine is a purine alkaloid and its biosynthesis occurs in young tea leaves and is regulated by several enzymes. The biosynthetic pathway in "C. sinensis" differs from other caffeine producing plants such as coffee or guyausa. Analysis of the pathway was carried out