Related Terms

• Alpha-tocopherol, aluminum, anthocyanins, antioxidants, beta-carotene, caffeine, calcium, camellia, Camellia assamica, Camellia sinensis, Camellia sinensis (L.) Kuntze, camellia tea, camellia thea, Camellia theifera, catechin, Chinese tea, copper, flavonoids, fluoride, folic acid, green tea, iron, Japanese tea, kaempferol, manganese, mercury, myricetin, oolong tea, oxalate, phenolic acids, phylloquinone, polyphenols, quercetin, riboflavin, rutin, tannic acid, té negro (Spanish), tea for America, Thea bohea, Thea sinensis, Thea viridis, theaflavin, theanine, thearubigins, theifers, total phosphate, trace elements, vitamins, white tea, zinc.

Background

• Black tea is made from the dried leaves of Camellia sinensis, a shrub native to southeastern Asia. Green tea, black tea, and oolong tea all come from the same plant. Black tea is a traditional beverage in Britain. The quality of tea depends on the age of the tea leaves.

• Black tea is a source of caffeine, which stimulates the heart and central nervous system, relaxes smooth muscle in the lungs, and promotes urination. One cup of tea contains about 50 milligrams of caffeine, depending on the strength and size of the cup, while coffee contains 65-175 milligrams of caffeine per cup. Tea also contains vitamins, a compound called tannin, and antioxidants called polyphenols.

• There is conflicting evidence for the use of black tea in preventing heart disease and cancer. Regular tea consumption may lower the risk of heart attacks and all-cause mortality, regardless of age, sex, smoking status, obesity, and medical history. There is preliminary evidence for the use of black tea in increasing bone marrow density (BMD), preventing osteoporosis in older women, and enhancing brain and muscle function. The evidence is also preliminary for the use of black tea as a mouthwash in the prevention of dental cavities.

Scientific Evidence

Tradition/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 health care professional.

• Acute pharyngitis (throat inflammation), allergies, antibacterial, antioxidant, anxiety, cancer multidrug resistance, cataract (eye disorder), circulatory/blood flow disorders (blood flow), cleansing, Crohn's disease (stomach disorder), diarrhea, diuretic (promotes urination), gum disease, headache, hyperactivity (children), immune enhancement/improving resistance to disease, influenza, intestinal flora - antibiotic resistant bacteria, joint pain, kidney stone prevention, melanoma (skin cancer), metabolic enhancement (improve metabolism), obesity, osteoarthritis (joint disorder), pain, prostate cancer, sickle cell anemia (blood disorder), stomach disorders, stroke, toxin/alcohol elimination from the body, trigeminal neuralgia (painful nerve disorder), vomiting.

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.

Adults (18 years and older)

• Note: Many studies have looked at the use of black tea for many different conditions. Dosing for studies that showed positive effects are presented below.

• To prevent dental cavities, 20 milliliters has been gargled in the mouth for 60 seconds.

• To treat diarrhea, 2-3 cups of black tea (240-320 milligrams of antioxidant content) have been taken by mouth daily.

• To prevent heart attack, five servings of black tea have been taken by mouth daily for three weeks. An unspecified dose of black tea has been taken by mouth for up to six weeks. Six grams of tea has been taken by mouth as a single dose. Four standard cups of black tea have been taken by mouth over 30 minutes. Five cups of black tea (250 milliliters each) have been taken by mouth daily for four weeks.

• To enhance memory, 400 milliliters of black tea has been taken by mouth three times daily.

• To prevent mouth cancer and/or leukoplakia (white patches in the mouth), black tea has been taken by mouth over one year.

• To stimulate and provide energy, seven or more cups of black tea have been taken by mouth daily (the effects may depend on the caffeine content).

• To manage stress, black tea has been taken by mouth for six weeks.

Children (younger than 18 years)

• There is no proven safe or effective dose for black tea in children.

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

• Avoid with known allergy or sensitivity to tea, any of its parts including caffeine or tannins, or members of the Theaceae family. Skin rash and hives due to caffeine consumption have been reported.

Side Effects and Warnings

• General: Side effects from black tea are mainly due to caffeine content. Black tea contains about 50 milligrams of caffeine per cup. When more than 500 milligrams of caffeine is consumed daily, both short-term and long-term side effects from caffeine are possible. Side effects of caffeine may be stronger in children and the elderly. Chronic caffeine use, especially in large amounts, may result in psychological dependence, and abruptly discontinuing caffeine intake may produce withdrawal symptoms such as anxiety, dizziness, headache, irritation, and nervousness. Applying Polyphenon E® (a product containing tea antioxidants) to the skin may result in skin irritation.

• Black tea is likely safe when taken by mouth in moderate amounts of up to eight cups daily. Traditionally, black tea is consumed throughout the day in many countries and is considered to be safe and nontoxic.

• Avoid in those with known allergy or sensitivity to tea, caffeine, or tannins. Skin rash and hives due to caffeine consumption have been reported.

• Black tea may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

• Black tea may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be increased in the blood and may cause increased effects or potentially serious adverse reactions. People using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

• Black tea may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

• Caution is advised in people taking drugs that lower blood pressure. Black tea may increase blood pressure, an effect that may be worsened with exercise, smoking, or stress.

• Use cautiously in people who are undergoing gastrointestinal magnetic resonance imaging (MRI) to look at stomach diseases.

• Use cautiously in people undergoing caffeine liver function tests, as black tea may affect the results.

• Use cautiously in firefighters wearing protective clothing. Black tea may increase the risk of heat-related fatigue and injury.

• Use cautiously in pregnant women, as caffeine may pass through the placenta to the baby. Black tea may disrupt the processing of folate, an important nutrient during pregnancy. Use cautiously in breastfeeding women, as caffeine may be transferred to the baby through breast milk.

• Extreme caution is needed in children who have epileptic apnea (seizures and breathing problems while sleeping). Avoid using in babies.

• Use cautiously in people who have abnormal heart rhythm, apnea (breathing problems during sleep), eating disorders, glaucoma, high cholesterol, increased caffeine sensitivity, iron deficiency, movement disorders, osteoporosis or a risk of osteoporosis, overactive bladder or other bladder disorders, psychiatric disorders, rosacea, a risk of cancer, a risk of gout, a risk of kidney stones, a risk of thromboembolic stroke, seizure disorders, or weakened immune systems.

• Use cautiously in people who are taking adenosine, agents that may affect blood vessel width, agents that may affect the immune system, agents that may cause uncontrolled muscle contractions, agents that may increase seizure risk, agents that may prevent seizures, alcohol, antibiotics (such as ciprofloxacin or enoxacin), antiulcer agents or cimetidine, beta-agonists, beta-blockers (including propranolol and timolol), carbamazepine, central nervous system depressants (such as benzodiazepines, including, but not limited to, diazepam, diuretics, triazolam, and midazolam), dexamethasone, dipyridamole, ephedra or ephedrine, estrogens or birth control, fluconazole, fluvoxamine, folate, furafylline, lithium, methoxsalen, mexiletine, milk with tetracycline antibiotics, nicotine, phenytoin, terbinafine, or theophylline.

• Avoid using in people who have autosomal recessive polycystic kidney disease, Marfan syndrome (a connective tissue disorder), mitral valve prolapse (a heart problem in which a valve does not close properly), or serious liver disorders. Avoid in those taking methylenedioxymethamphetamine (MDMA, or "Ecstasy").

• Avoid in patients with allergy of sensitivity to tea, any of its constituents including caffeine or tannins, or members of the Theaceae family.

• Black tea may also cause side effects, such as abnormally early or fast heartbeat, addiction, anemia, anxiety, bedwetting, blurred vision, breakdown of muscle fibers (resulting in myoglobin protein in the urine), changes in concentration, changes in memory, changes in seizure duration, changes in voice quality, constipation, damage to tooth surfaces, decreased bone mineral density in neck bone, decreased reaction time, decreased testicle size, delirium, depression, euphoria, fatigue, gas, headache, heart palpitations, impaired sperm production, increased alertness, increased eye pressure, increased motor activity, increased risk of fibrocystic breast disease, increased risk of iron deficiency, increased risk of multiple sclerosis, kidney damage, liver poisoning, nausea, mild muscle pain, muscle spasms, muscle tension, painful urination, pemphigus (a chronic skin disorder that causes blisters), physical symptoms linked to mental disorders, bipolar disorder, seizures, sleep problems, stiff arteries, stomachache, teeth staining, trigeminal neuralgia (a painful nerve disorder), ulcer symptoms, unpleasant mood or irritability, unusual thoughts, upset stomach, and worsened symptoms of unstable bladder.

Pregnancy and Breastfeeding

• Use cautiously in pregnant women, as caffeine may pass through the placenta to the baby. The U.S. Food and Drug Administration (FDA) has advised that women who are or may become pregnant avoid products that contain caffeine. Some studies suggest that caffeine may affect a baby's development. Caffeine has been linked to miscarriage, premature birth, low birthweight, breathing difficulties or weakened immune system in the baby, and sudden infant death syndrome in some studies. Black tea may disrupt the processing of folate, an important nutrient during pregnancy. More results are needed to confirm these preliminary findings.

• Preliminary research found a possible link between tea and fertility. High caffeine consumption may delay conception in nonsmoking women.

• Use cautiously in breastfeeding women, as caffeine may be transferred to the baby through breast milk.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. 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.

Interactions with Drugs

• General: Drug interactions linked to black tea are mostly based on theory. They are generally based on the side effects profile of caffeine.

• Black tea may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

• Black tea may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking insulin or drugs for diabetes by mouth should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

• Black tea may cause low blood pressure. Caution is advised in people taking drugs that lower blood pressure.

• Black tea may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be increased in the blood and may cause increased effects or potentially serious adverse reactions. People using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

• Black tea may also interact with acetaminophen, adenosine, agents that may affect blood vessel width, agents that may affect the immune system, agents that may increase the risk of seizure, agents that may promote urination, agents that may treat osteoporosis, agents that may treat skin disorders, alcohol, amphetamine, antibiotics, anticancer agents, antidepressants, anti-inflammatories, antipsychotics, antiulcer agents, aspirin, benzodiazepines, beta-agonists, beta-blockers, birth control, caffeine, calcium salts, carbamazepine, central nervous system depressants, cholesterol-lowering agents, clozapine, dexamethasone, dipyridamole, disulfiram, ephedrine, ergot derivatives, estrogens, flubendiamide, fluconazole, fluoride, fluvoxamine, furafylline, hydrocortisone, inotropes, iron salts, lithium, methoxsalen, methylenedioxymethamphetamine (MDMA, or "Ecstasy"), methylphenidate, mexiletine, monoamine oxidase inhibitors (MAOIs), nicotine, opiates, oseltamivir, pain relievers, perazine, phenytoin, potassium dichromate, proton pump inhibitors (PPIs), quinolones, riluzole, sedatives, teeth-whitening agents, terbinafine, tetracyclines, theophylline, and verapamil.

Interactions with Herbs and Dietary Supplements

• General: Herb and supplement interactions linked to black tea are mostly based on theory. They are generally based on the side effects profile of caffeine.

• Black tea may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.

• Black tea may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of other herbs or supplements may become too high in the blood. It may also alter the effects that other herbs or supplements possibly have on the cytochrome P450 system.

• Black tea may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

• Black tea may cause low blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.

• Black tea may also interact with antibacterials, anticancer herbs and supplements, antidepressants, anti-inflammatories, antiobesity herbs and supplements, antioxidants, antipsychotics, antiulcer herbs and supplements, birth control, bitter orange, caffeine-containing herbs and supplements, calcium, capsicum, cholesterol-lowering herbs and supplements, cola nut, cordyceps, damiana, danshen, dental herbs and supplements, echinacea, ephedra (ma huang), fluoride, folate, guarana, herbs and supplements that may affect blood vessel width, herbs and supplements that may affect the immune system, herbs and supplements that may enhance mental or physical performance, herbs and supplements that may increase seizure risk, herbs and supplements that may promote urination, herbs and supplements that may treat osteoporosis, herbs and supplements that may treat skin disorders, inotropes, iron, magnesium, mate, monoamine oxidase inhibitors (MAOIs), nicotine or tobacco, pain relievers, phytoestrogens, rutin-containing herbs and supplements, sedatives, tannin-containing herbs and supplements, thiamine, vitamin E, and yerba mate.

Author Information

• This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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