Black tea (Camellia sinensis)

Black tea (Camellia sinensis)

Background

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 5000 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.

Synonyms

Camellia assamica, camellia tea, camellia, Camellia sinensis , catechin, Chinese tea, tea for America, theifers, Thea sinensis, Thea bohea, Thea viridis.

Note : Also see information on green tea .

Evidence

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.

Uses based on scientific evidenceGrade*Cancer prevention
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. Some animal and laboratory research suggests that components of black tea may be carcinogenic, although effects in humans are not clear. Overall, the relationship of black tea consumption and human cancer remains undetermined.

C

Heart attack prevention / cardiovascular risk
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. One study reports that regular ingestion of black tea does not alter plasma homocysteine concentrations.

C

Mental performance/alertness
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.

C

Memory enhancement
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.

C

Dental cavity prevention
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.

C

Osteoporosis prevention
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.

C

Asthma
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.

C

Methicillin-resistant Staphylococcus aureus (MRSA) infection
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.

C

ya you betcha

* Key to grades
A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use (it may not work);
F: Strong scientific evidence against this use (it likely does not work).

Uses based on tradition or theory
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Acute pharyngitis, antioxidant, anxiety, cancer multidrug resistance, circulatory/blood flow disorders, "cleansing," colorectal cancer, Crohn's disease, diabetes, diarrhea, diuretic (increasing urine flow), energy metabolism, gum disease, headache, hyperactivity (children), immune enhancement/improving resistance to disease, influenza, joint pain, kidney stone prevention, melanoma, obesity, osteoarthritis, pain, prostate cancer, stomach disorders, toxin/alcohol elimination from the body, trigeminal neuralgia, vomiting, weight loss.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adult oral dosing (18 years and older):

Black tea has not been proven as an effective therapy for any condition, and benefits of specific doses are not established. For heart disease prevention, studies have evaluated 250 to 900 milliliters of tea, consumed daily for up to four weeks. For cognitive performance, an example dose used in research is 400 milliliters of black tea taken three times daily. For dental cavity prevention, 20 milliliters of black tea gargled for 60 seconds daily has been studied.

One cup of tea contains approximately 50 milligrams of caffeine, depending on the strength and size of cup.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

People with known allergy/hypersensitivity to caffeine or tannin should avoid black tea. Skin rash and hives have been reported with caffeine ingestion.

Side Effects and Warnings

Studies of the side effects of black tea specifically are limited. However, black tea is a source of caffeine, for which multiple reactions are reported.

Caffeine is a stimulant of the central nervous system, and may cause insomnia in adults, children, and infants (including nursing infants of mothers taking caffeine). Caffeine acts on the kidneys as a diuretic (increasing urine and urine sodium/potassium levels, and potentially decreasing blood sodium/potassium levels), and may worsen urge incontinence. Caffeine-containing beverages may increase the production of stomach acid, and may worsen ulcer symptoms. Tannin in tea can cause constipation. Caffeine in doses of 250 to 350 milligrams can increase heart rate and blood pressure, although people who consume caffeine regularly do not seem to experience these effects in the long-term.

An increase in blood sugar levels may occur after drinking black tea containing the equivalent of 200 milligrams of caffeine (4 to 5 cups, depending on tea strength and cup size). Caffeine-containing beverages such as black tea should be used cautiously in patients with diabetes. People with severe liver disease should use caffeine cautiously, as levels of caffeine in the blood may build up and last longer. Skin rashes have been associated with caffeine ingestion. In laboratory and animal studies, caffeine has been found to affect blood clotting, although effects in humans are not known.

Caffeine toxicity/high doses : When the equivalent or more than 500 milligrams of caffeine are consumed (usually more than 8 to 10 cups per day, depending on strength and size of cups), symptoms of anxiety, delirium, agitation, psychosis, or detrussor instability (unstable bladder) may occur. Conception may be delayed in women who consume large amounts of caffeine. Seizure, muscle spasm, life-threatening muscle breakdown (rhabdomyolysis), and life-threatening abnormal heart rhythms have been reported with caffeine overdose. Doses greater than 1000 milligrams may be fatal.

Caffeine withdrawal : Chronic use can result in tolerance, psychological dependence, and may be habit forming. Abrupt discontinuation may result in withdrawal symptoms such as headache, irritation, nervousness, anxiety, tremor, or dizziness. In people with psychiatric disorders such as affective disorder or schizoaffective disorder, caffeine withdrawal may worsen symptoms or cause confusion, disorientation, excitement, restlessness, violent behavior, or mania.

Chronic effects : Several population studies initially suggested a possible association between caffeine use and fibrocystic breast disease, although more recent research has not found this connection. Limited research reports a possible relationship between caffeine use and multiple sclerosis, although evidence is not definitive in this area. Animal study reports that tannin fractions from tea plants may increase the risk of cancer, although it is not clear that the tannin present in black tea has significant carcinogenic effects in humans.

Drinking tannin-containing beverages such as tea may contribute to iron deficiency, and in infants, tea has been associated with impaired iron metabolism and microcytic anemia.

Pregnancy and Breastfeeding

Large amounts of black tea should be used cautiously in pregnant women, as caffeine crosses the placenta and has been associated with spontaneous abortion, intrauterine growth retardation, and low birth weight. Heavy caffeine intake (400 milligrams per day or greater) during pregnancy may increase the risk of later developing SIDS (sudden infant death syndrome). Very high doses of caffeine (greater than or equal to 1100 milligrams daily) have been associated with birth defects, including limb and palate malformations.

Caffeine is readily transferred into breast milk. Caffeine ingestion by infants can lead to sleep disturbances/insomnia. Infants nursing from mothers consuming greater than 500 milligrams of caffeine daily have been reported to experience tremors and heart rhythm abnormalities. Components present in breast milk may reduce infants' ability to metabolize caffeine, resulting in higher than expected blood levels. Tea consumption by infants has been associated with anemia, reductions in iron metabolism, and irritability.

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January 01, 2004