Black tea (Camellia sinensis)

Black tea is made from the dried leaves of Camellia sinensis, a perennial evergreen shrub. Black tea has a long history of use, dating back to China approximately 5,000 years ago. Green tea, black tea, and oolong tea are all derived from the same plant.

Black tea is a source of caffeine, a methylxanthine which stimulates the central nervous system, relaxes smooth muscle in the airways to the lungs (bronchioles), stimulates the heart, and acts on the kidney as a diuretic (increasing urine). One cup of tea contains approximately 50 milligrams of caffeine, depending on the strength and size of cup (as compared to coffee which contains 65 to 175 milligrams of caffeine per cup). Tea also contains polyphenols (catechins, anthocyanins, phenolic acids), tannin, trace elements, and vitamins.

The tea plant is native to Southeast Asia that can grow up to a height of 40 feet, but is usually maintained at a height of two to three feet by regular pruning. The first spring leaf buds, called the first flush, are considered the highest-quality leaves. When the first flush leaf bud is picked, another one grows, which is called the second flush, and this continues until an autumn flush. The older leaves picked farther down the stems are considered to be of poorer quality.

Tea varieties reflect the growing region (for example, Ceylon or Assam), the district (for example, Darjeeling), the form (for example, pekoe is cut, gunpowder is rolled), and the processing method (for example, black, green, or oolong). India and Sri Lanka are the major producers of black tea.

Historically, tea has been served as a part of various ceremonies, and has been used to stay alert during long meditations. A legend in India describes the story of Prince Siddhartha Gautama, the founder of Buddhism, who tore off his eyelids in frustration at his inability to stay awake during meditation while journeying through China. A tea plant is said to have sprouted from the spot where his eyelids fell, providing him with the ability to stay awake, meditate, and reach enlightenment. Turkish traders reportedly introduced tea to Western cultures in the 6th century. By the 18th Century, tea was commonly consumed in England, where it became customary to drink tea at 5pm.

Black tea reached the Americas with the first European settlers in 1492. Black tea gained notoriety in the U.S. in 1773 when colonists tossed black tea into Boston Harbor during the Boston Tea Party. This symbolic gesture was an early event in the U.S. War of Independence against England.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Asthma (Grade: C)
Research has shown caffeine to cause improvements in airflow to the lungs (bronchodilation). However, it is not clear if caffeine or tea use has significant clinical benefits in people with asthma. Better research is needed in this area before a conclusion can be drawn.

Cancer prevention (Grade: C)
Several studies have explored a possible association between regular consumption of black tea and rates of cancer in populations. This research has yielded conflicting results, with some studies suggesting benefits, and others reporting no effects. Laboratory and animal studies report that components of tea, such as polyphenols, have antioxidant properties and effects against tumors. However, effects in humans remain unclear, and these components may be more common in green tea rather than in black tea.

Dental cavity prevention (Grade: C)
There is limited study of black tea as a mouthwash for the prevention of dental cavities (caries). It is not clear if this is a beneficial therapy.

Heart attack prevention / cardiovascular risk (Grade: C)
There is conflicting evidence from a small number of studies examining the relationship of tea intake with the risk of heart attack. Tea may reduce the risk of platelet aggregation or endothelial dysfunction, proposed to be beneficial against blockage of arteries in the heart. The long-term effects of tea consumption on cardiovascular risk factors such as cholesterol levels, blood pressure, and atherosclerosis are not known.

Memory enhancement (Grade: C)
Several preliminary studies have examined the effects of caffeine, tea, or coffee use on short and long-term memory. It remains unclear if tea is beneficial for this use.

Mental performance/alertness (Grade: C)
Limited, low-quality research reports that the use of black tea may improve cognition and sense of alertness. Black tea contains caffeine, which is a stimulant.

Methicillin-resistant Staphylococcus aureus (MRSA) infection (Grade: C)
In one small study, inhaled tea catechin was reported as temporarily effective in the reduction of MRSA and shortening of hospitalization in elderly patients with MRSA infected sputum. Additional research is needed to further explore these results.

Oral leukoplakia/ carcinoma (Grade: C)
Early studies report that black tea may lead to clinical improvement in oral leukoplakia and therefore prevent oral carcinoma. Further research is needed to confirm these results.

Osteoporosis prevention (Grade: C)
Preliminary research suggests that chronic use of black tea may improve bone mineral density (BMD) in older women. Better research is needed in this area before a conclusion can be drawn.

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Note: Also see information on green tea.