Two principal varieties of the species are used, the small-leaved Chinese variety plant (C. sinensis sinensis), also used for green and white teas, and the large-leaved Assamese plant (C. sinensis assamica), which was traditionally only used for black tea, although in recent years some green has been produced.

Black Tea Research

* A long-term study by the Netherlands National Institute of Public Health and the Environment found a correlation between regular consumption of black tea and reduced risk of stroke. Researchers looked at data from a study examining the health benefits of foods that are high in flavonoids - phytonutrients with antioxidant benefits. While some of the flavonoids were obtained from fruits and vegetables, seventy percent came from black tea. The study looked at 552 men over a 15 year period. Researchers concluded that the flavonoids in black tea helped reduce the production of LDL - the "bad" cholesterol that can lead to stroke and heart attacks. Furthermore, men who drank over four cups of black tea per day had a significantly lower risk of stroke than men who drank only two to three cups per day.

* A separate study by Dr. Joseph Vita at Boston's School of Medicine supported these results. For four months, sixty-six men drank four cups of either black tea or a placebo daily. Dr. Vita concluded that drinking black tea can help reverse an abnormal functioning of the blood vessels that can contribute to stroke or heart attack. Furthermore, improvement in the functioning of the blood vessels was visible within two hours of drinking just one cup of black tea.

* Finally, a study of over 3,000 adults in Saudi Arabia - where black tea is favored over green - found that regular consumption of the dark brew can reduce the risk of coronary heart disease by fifty percent.

Black tea is often blended and mixed with various other plants in order to obtain a beverage.

* Earl Grey: black tea with bergamot oil.

* English Breakfast: described as full-bodied, robust, and/or rich, and blended to go well with milk and sugar.

* Irish Breakfast: it is a blend of several black teas: most often Assam teas and, less often, other types of black tea.

* In the United States, citrus fruits such as orange or lemon, or their respective rinds, are often used to create flavored black teas, sometimes in conjunction with spices (such as cinnamon). These products can be easily confused with citrus-based herbal teas, but the herbal products will generally be labelled as having no caffeine; whereas, the tea-based products do contain caffeine.