What is it?
Black tea is a product made from the Camellia sinesis plant. The aged leaves and stems are used to make medicine. Green tea, which is made from fresh leaves of the same plant, has some different properties.
Black tea is used for improving mental alertness as well as learning, memory and information processing skills. It is also used for treating headache and low blood pressure; preventing heart disease, including “hardening of the arteries” (atherosclerosis) and heart attack; preventing Parkinson's disease; and reducing the risk of stomach and colon cancer, lung cancer, ovarian cancer, and breast cancer. It is also used for type 2 diabetes, stomach disorders, vomiting, diarrhea, and as a diuretic to increase urine flow. Some people use black tea for preventing tooth decay and kidney stones. In combination with various other products, black tea is used for weight loss.
In foods, black tea is consumed as a hot or cold beverage.
How effective is it?
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
The effectiveness ratings for BLACK TEA are as follows:
Likely effective for...
- Mental alertness. Drinking black tea and other caffeinated beverages throughout the day helps to keep people alert, even after extended periods without sleep.
Possibly effective for...
- Preventing dizziness upon standing up (orthostatic hypotension) in older people. Black tea works for this condition because it raises blood pressure.
- Reducing the risk of heart attacks. There is some evidence that people who drink black tea have a lower risk of heart attack. If they do have a heart attack, they are less likely to die if they have been drinking black tea for at least a year.
- Reducing the risk of kidney stones. Women who drink black tea seem to have an 8% lower risk of developing kidney stones.
- Reducing the risk of Parkinson's disease. There is some evidence from large-scale studies that people who drink caffeinated beverages such as coffee, tea, and cola have a decreased risk of Parkinson's disease. For men, the effects seem to be dose-related. For example, men consuming a total of 421-2716 mg of caffeine daily seem to have the greatest reduction in risk. However, there seems to be a significant reduction in risk even with consumption of as little as 124-208 mg caffeine per day. In women, the effects do not seem to be dose- related. Moderate consumption of caffeine (about one to four cups black tea daily) seems to provide the most reduction in risk. Drinking black tea also appears to reduce the occurrence of Parkinson's disease among people who smoke.
- Reducing the risk of ovarian cancer. Women who regularly drink tea, including black tea or green tea, appear to have a significantly lower risk of developing ovarian cancer compared to women who never or seldom drink tea.
- Reducing the risk of hardening of the arteries (atherosclerosis), especially in women.
Possibly ineffective for...
- Reducing the risk of stomach, colon, and rectal cancer.
- Reducing the risk of breast cancer.
Insufficient evidence to rate effectiveness for...
- Brittle bones (osteoporosis). So far there is some evidence that drinking black tea might be linked to stronger bones in women aged 65-76 years. Drinking black tea also seems to be associated with a lower risk of hip fracture in men and women who are older than 50.
- Type 2 diabetes. Some research suggests that Japanese adults who drink a cup or more of black tea daily do not have a lower risk of developing type 2 diabetes compared to those who drink less than a cup daily.
- Lung cancer. There is evidence that men who get more chemicals called phytoestrogens in their diet have up to a 27% lower risk of developing lung cancer than men who do not get these chemicals. Green tea and black tea contain phytoestrogens.
- Stomach disorders.
- High blood pressure.
- Preventing tooth decay.
- Reducing the risk of other cancers.
- Promoting weight loss.
- Other conditions.
More evidence is needed to rate the effectiveness of black tea for these uses.
Black tea contains 2% to 4% caffeine, which affects thinking and alertness, increases urine output, and may reduce the symptoms of Parkinson's disease. It also contains antioxidants and other substances that might help protect the heart and blood vessels.
Black tea is safe for most adults. Too much black tea, such as more than five cups per day, can cause side effects because of the caffeine. These side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion.
People who drink black tea or other caffeinated beverages all the time, especially in large amounts, can develop psychological dependence.
Caffeine is PROBABLY SAFE in children in amounts commonly found in foods.
Special precautions & warnings:
Pregnancy and breast-feeding: If you are pregnant or breast-feeding, black tea in small amounts is probably not harmful. Do not drink more than 2 cups a day of black tea. This amount of tea provides about 200 mg of caffeine. Consuming more than this amount during pregnancy has been linked to an increased risk of miscarriage and other negative effects, including symptoms of caffeine withdrawal in newborns and lower birth weight.
If you are breast-feeding, drinking more than 2 cups a day of black tea might cause your baby to become more irritable and have more bowel movements.
Anemia: Drinking black tea may make anemia worse in people with iron deficiency.
Anxiety disorders: The caffeine in black tea might make these conditions worse.
Bleeding disorders: There is some reason to believe that the caffeine in black tea might slow blood clotting, though this hasn’t been shown in people. Use caffeine cautiously if you have a bleeding disorder.
Heart problems: Caffeine in black tea can cause irregular heartbeat in certain people. If you have a heart condition, use caffeine with caution.
Diabetes: The caffeine in black tea might affect blood sugar. Use black tea with caution if you have diabetes.
Diarrhea: Black tea contains caffeine. The caffeine in black tea, especially when taken in large amounts, can worsen diarrhea.
Irritable bowel syndrome (IBS): Black tea contains caffeine. The caffeine in black tea, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.
Glaucoma: Drinking caffeinated black tea increases the pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes.
Hormone-sensitive condition such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Black tea might act like estrogen. If you have any condition that might be made worse by exposure to estrogen, don’t use black tea.
High blood pressure: The caffeine in black tea might increase blood pressure in people with high blood pressure. However, this doesn't seem to occur in people who drink black tea or other caffeinated products regularly.
Brittle bones (osteoporosis): Drinking caffeinated black tea can increase the amount of calcium that is flushed out in the urine. This might weaken bones. Don’t drink more than 300 mg of caffeine per day (approximately 2-3 cups of black tea). Taking extra calcium may help to make up for calcium losses. Older women who have a genetic condition that affects the way they use vitamin D, should use caffeine with caution.
Be cautious with this combination.
Black tea contains caffeine. The caffeine in black tea might block the affects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop drinking black tea or other caffeine-containing products at least 24 hours before a cardiac stress test.
Antibiotics (Quinolone antibiotics)
The body breaks down caffeine to get rid of it. Some antibiotics might decrease how quickly the body breaks down caffeine. Taking these antibiotics along with black tea can increase the risk of side effects including jitteriness, headache, increased heart rate, and other side effects.
Some antibiotics that decrease how quickly the body breaks down caffeine include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), trovafloxacin (Trovan), and grepafloxacin (Raxar).
Black tea contains caffeine. The body breaks down caffeine to get rid of it. Cimetidine (Tagamet) can decrease how quickly your body breaks down caffeine. Taking cimetidine (Tagamet) along with black tea might increase the chance of caffeine side effects including jitteriness, headache, fast heartbeat, and others.
The body breaks down clozapine (Clozaril) to get rid of it. The caffeine in black tea seems to decrease how quickly the body breaks down clozapine (Clozaril). Taking black tea along with clozapine (Clozaril) can increase the effects and side effects of clozapine (Clozaril).
Black tea contains caffeine. The caffeine in black tea might block the affects of dipyridamole (Persantine). Dipyridamole (Persantine) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop drinking black tea or other caffeine-containing products at least 24 hours before a cardiac stress test.
The body breaks down caffeine to get rid of it. Disulfiram (Antabuse) can decrease how quickly the body gets rid of caffeine. Taking black tea (which contains caffeine) along with disulfiram (Antabuse) might increase the effects and side effects of caffeine including jitteriness, hyperactivity, irritability, and others.
Stimulant drugs speed up the nervous system. Black tea contains caffeine. Caffeine and ephedrine are both stimulant drugs. Taking black tea along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems. Do not take caffeine containing products and ephedrine at the same time.
The body breaks down the caffeine in black tea to get rid of it. Estrogens can decrease how quickly the body breaks down caffeine. Taking estrogen pills and drinking black tea can cause jitteriness, headache, fast heartbeat, and other side effects. If you take estrogen pills, limit your caffeine intake.
Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.
The body breaks down the caffeine in black tea to get rid of it. Fluvoxamine (Luvox) can decrease how quickly the body breaks down caffeine. Taking caffeine along with fluvoxamine (Luvox) might cause too much caffeine in the body, and increase the effects and side effects of caffeine.
Your body naturally gets rid of lithium. The caffeine in black tea can increase how quickly your body gets rid of lithium. If you take products that contain caffeine and you take lithium, stop taking caffeine products slowly. Stopping caffeine too quickly can increase the side effects of lithium.
Medications for asthma (Beta-adrenergic agonists)
Black tea contains caffeine. Caffeine can stimulate the heart. Some medications for asthma can also stimulate the heart. Taking caffeine with some medications for asthma might cause too much stimulation and cause heart problems.
Some medications for asthma include albuterol (Proventil, Ventolin, Volmax), metaproterenol (Alupent), terbutaline (Bricanyl, Brethine), and isoproterenol (Isuprel).
Medications for depression (MAOIs)
The caffeine in black tea can stimulate the body. Some medications used for depression can also stimulate the body. Drinking black tea and taking some medications for depression might cause too much stimulation of the body and serious side effects including fast heartbeat, high blood pressure, nervousness, and others.
Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.
Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)
Black tea might slow blood clotting. Taking black tea along with medications that also slow clotting might increase the chances of bruising and bleeding.
Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, warfarin (Coumadin), and others.
The stimulant effects of the caffeine in black tea can block the sleep-producing effects of pentobarbital.
The caffeine in black tea can stimulate the body. Phenylpropanolamine can also stimulate the body. Taking caffeine and phenylpropanolamine together might cause too much stimulation and increase heartbeat, blood pressure, and cause nervousness.
The body breaks down riluzole (Rilutek) to get rid of it. Drinking black tea can decrease how quickly the body breaks down riluzole (Rilutek) and increase the effects and side effects of riluzole.
Stimulant drugs speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and speed up your heartbeat. The caffeine in black tea can also speed up the nervous system. Drinking black tea along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with black tea.
Some stimulant drugs include diethylpropion (Tenuate), epinephrine, phentermine (Ionamin), pseudoephedrine (Sudafed), and many others.
Black tea contains caffeine. Caffeine works similarly to theophylline. Caffeine can also decrease how quickly the body gets rid of theophylline. This might cause increased effects and side effects of theophylline.
Verapamil (Calan, Covera, Isoptin, Verelan)
The body breaks down the caffeine in black tea to get rid of it. Verapamil (Calan, Covera, Isoptin, Verelan) can decrease how quickly the body gets rid of caffeine. Drinking black tea and taking verapamil (Calan, Covera, Isoptin, Verelan) can increase the risk of side effects for caffeine including jitteriness, headache, and an increased heartbeat.
Warfarin (Coumadin) is used to slow blood clotting. Large amounts of black tea might decrease how well warfarin (Coumadin) slows blood clotting. Decreasing how well warfarin (Coumadin) slows blood clotting might increase the risk of clotting. It is unclear why this interaction might occur. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
Be watchful with this combination.
The body breaks down the caffeine in black tea to get rid of it. Alcohol can decrease how quickly the body breaks down caffeine. Taking black tea along with alcohol might cause too much caffeine in the bloodstream and caffeine side effects including jitteriness, headache, and fast heartbeat.
Birth control pills (Contraceptive drugs)
The body breaks down the caffeine in black tea to get rid of it. Birth control pills can decrease how quickly the body breaks down caffeine. Taking black tea along with birth control pills can cause jitteriness, headache, fast heartbeat, and other side effects.
Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.
Black tea contains caffeine. The body breaks down caffeine to get rid of it. Fluconazole (Diflucan) might decrease how quickly the body gets rid of caffeine. This could cause caffeine to stay in the body too long and increase the risk of side effects such as nervousness, anxiety, and insomnia.
Medications for depression (Tricyclic antidepressants)
Black tea contains chemicals called tannins. Tannins can bind to many medications and decrease how much medicine the body absorbs. To avoid this interaction, avoid black tea 1 hour before and 2 hours after taking medications for depression called tricyclic antidepressants.
Some medications for depression include amitriptyline (Elavil) or imipramine (Tofranil, Janimine).
Medications for diabetes (Antidiabetes drugs)
Black tea might increase blood sugar. Diabetes medications are used to lower blood sugar. By increasing blood sugar, black tea might decrease the effectiveness of diabetes medications. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.
Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.
Black tea contains caffeine. The body breaks down caffeine to get rid of it. Mexiletine (Mexitil) can decrease how quickly the body breaks down caffeine. Taking Mexiletine (Mexitil) along with black tea might increase the caffeine effects and side effects of black tea.
Black tea contains chemicals called tannins. Tannins can bind to many medications and decrease how much medicine the body absorbs. To avoid this interaction, avoid black tea 1 hour before and 2 hours after taking phenothiazine medications.
Some phenothiazine medications include fluphenazine (Permitil, Prolixin), chlorpromazine (Thorazine), haloperidol (Haldol), prochlorperazine (Compazine), thioridazine (Mellaril), and trifluoperazine (Stelazine).
The body breaks down the caffeine in black tea to get rid of it. Terbinafine (Lamisil) can decrease how quickly the body gets rid of caffeine and increase the risk of side effects including jitteriness, headache, increased heartbeat, and other effects.
Using bitter orange along with other products that contain caffeine, such as black tea, can increase blood pressure and heart rate in otherwise healthy adults with normal blood pressure. This could increase the risk of serious heart problems.
Caffeine-containing herbs and supplements
Black tea contains caffeine. Using it along with other herbs and supplements that contain caffeine might increase the risk of caffeine side effects. Natural products that contain caffeine include coffee, black tea, green tea, oolong tea, guarana, mate, and others.
High caffeine intake from foods and beverages, including black tea, flushes calcium out of the body in the urine.
There is some concern that combining caffeine, an ingredient in black tea, with ephedra and creatine might increase the risk of serious harmful effects. There is a report of stroke in an athlete who consumed 6 grams of creatine monohydrate, 400-600 mg of caffeine, 40-60 mg of ephedra, and a variety of other supplements daily for 6 weeks. Caffeine might also decrease whatever benefit creatine might have on athletic performance.
Ephedra (Ma huang)
Ephedra and black tea are both stimulants. They speed up the central nervous system. Using them together might speed it up too much, increasing the risk of high blood pressure, heart attack, stroke, seizures, and death. Don't take black tea with ephedra or other stimulants.
Herbs and supplements that might slow blood clotting
Black tea might slow blood clotting. Using it along with other herbs and supplements that might also slow blood clotting could increase the risk of bruising and bleeding in some people. Some of these herbs include angelica, clove, danshen, garlic, ginger, ginkgo, Panax ginseng, and others.
Black tea might interfere with the body's ability to absorb iron. This probably isn't a problem for most people, unless they are iron-deficient. If this is the case, drink tea between meals rather than with meals to lessen this interaction.
Black tea contains caffeine. Using herbs and supplements that contain caffeine can speed up the removal of lithium from the body.
Drinking large amounts of black tea can increase the amount of magnesium that is flushed out in the urine.
Black tea might interfere with the body's ability to absorb iron. This probably isn't a problem for most people, unless they are iron-deficient. If this is the case, drink tea between meals rather than with meals to lessen this interaction.
Adding milk to black tea appears to reduce some of the heart health benefits of drinking tea. Milk might bind with the antioxidants in tea and keep them from being absorbed. However, not all research confirms this. More evidence is needed to determine just how important this interaction, if any, might be.
An 8-ounce serving of black tea provides from 40-120 mg of caffeine, the active ingredient.
The following doses have been studied in scientific research:
- For headache or improving mental alertness: a typical dose is up to 250 mg of caffeine (several cups of black tea) per day.
- For reducing the risk of heart attack and kidney stones: a dose of at least one cup per day.
- For preventing "hardening of the arteries" (atherosclerosis), 125-500 mL (1-4 cups) of brewed black tea daily.
- For preventing Parkinson's disease: men drinking 421-2716 mg of total caffeine (approximately 5-33 cups of black tea) daily have the lowest risk of developing Parkinson's disease, when compared to other men. However, men who drink as little as 124-208 mg of caffeine (approximately 1-3 cups of black tea) daily also have a significantly lower chance of developing Parkinson's disease. In women, moderate caffeine intake (1-4 cups of black tea) per day seems to be best.
Black Leaf Tea, Camellia sinensis, Camellia thea, Camellia theifera, Chinese Tea, English Tea, Feuille de Thé Noir, Té Negro, Tea, Thé Anglais, Thé Noir, Thea bohea, Thea sinensis, Thea viridis, Theaflavin, Théaflavine.
To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.methodology (http://www.nlm.nih.gov/medlineplus/druginfo/natural/methodology.html).
To see all references for the Black tea page, please go to http://www.nlm.nih.gov/medlineplus/druginfo/natural/997.html.
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