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Also indexed as: Black Tea, Chai, Decaffeinated Tea, Green Tea, Herbal Teas, Instant Tea, Maté, Semi-Fermented Tea, Yerba Maté
The exact origin of tea is unknown, but one legend points to Prince Dharuma (also called Bodhidharma, founder of Zen Buddhism), who traveled from India to China around 500 A.D. on a spiritual journey. When he arrived in Canton, he vowed to sit, without sleeping, to atone for his sins. And sit he did, for nine long years, until one day he fell into a deep slumber. Upon awakening, he was so angry with himself that he cut off his eyelids and threw them on the ground; where the eyelids touched the ground, a tea bush sprang up. It was said that the bush was a reminder of our human weakness, and that drinking the leaves of this plant would strengthen resolve and diminish the desire to sleep.
More factual accounts hold that Chinese emperor Shen Nung “discovered” the tea plant around 2700 B.C., when bits of the tea leaves fell into a pot of boiling water and produced a fragrant brew.
All teas, excluding herbal varieties, come from the tea plant, Camellia sinensis. Black, green, and oolong are considered the basic types of teas, but thousands of varieties exist. Black tea is the most common form of tea worldwide. It is prepared from green tea leaves that have been allowed to oxidize, or ferment, to form a reddish brew. Oolong tea is a lightly fermented tea, between green and black tea on a continuum. Green tea is an unfermented, dried tea.
Variations in flavor, color, and strength are based on factors in growing, harvesting, and processing. Tea leaves fresh from the bush are harsh and bland. Processing methods largely determine the end flavor of the tea. Teas may also be blended to create variations on flavors, and may be flavored with other ingredients, such as jasmine or bergamot.
Herbal tea—technically not “tea” at all—uses a blend of dried plant flowers, stems, roots, or leaves for a hot brew. Organic varieties are available.
Tea preparation is an art. For the best tea, start with a ceramic teapot with a lid. Rinse the teapot with hot water to warm it, then add one teaspoon of tea or one tea bag for each cup (250mL) of water. In a tea kettle, bring water to a full boil—water at a bubbling boil agitates the tea leaves and causes them to open, for the full extraction of flavor. Pour boiling water over the tea bags or tea leaves in the teapot, and steep for a full three to five minutes. Flavor and caffeine are dissolved earliest, and the longer the tea is allowed to brew, the more tannin—the compound that gives tea its pungency and body—is allowed to dissolve into the brew. After steeping, remove tea bags or strain tea through a fine mesh tea strainer. Serve tea piping hot with sugar or honey and milk or lemon, or straight.
Preparation methods also add character. Try yerba mate—the potent Argentinean favorite—with a touch of vanilla and milk to soften the vigorous flavor. Karkade, a traditional Egyptian tea, consists of brewed hibiscus flowers and copious quantities of sugar. Moroccan mint tea—a strong, heavily sweetened brew of spearmint leaves—is traditionally served after meals in the Middle East. White coffee, a Lebanese favorite, is a tea-like concoction made with orange flowers and sugar, and served hot in demitasse glasses.
Tea (black), 1 cup (170g)
Calories: 1.7
Protein: 0.0g
Carbohydrate: 0.5g
Total Fat: 0.0g
*Foods that are an “excellent source” of a particular nutrient provide 20% or more of the Recommended Daily Value, based upon United States Department of Agriculture (USDA) guidelines. Foods that are a “good source” of a particular nutrient provide between 10 and 20% of the USDA Recommended Daily Value. Nutritional information and daily nutritional guidelines may vary in different countries. Please consult the appropriate organization in your country for specific nutritional values and the recommended daily guidelines.
People with high levels of anxiety appear to be more susceptible to the actions of caffeine. All sources of caffeine should be avoided, including caffeine-containing tea.
Chamomile tea is an old folk remedy for anxiety, particularly when it causes insomnia. Often 1 cup of tea is taken three or more times per day.
Caffeine may improve cognitive performance. Higher levels of coffee consumption were associated with improved cognitive performance in elderly British people in a preliminary study. Older people appeared to be more susceptible to the performance-improving effects of caffeine than were younger people. Similar but weaker associations were found for tea consumption. These associations have not yet been studied in clinical trials.
Quercetin, a flavonoid found in black and green tea protects LDL (“bad”) cholesterol against oxidation. Oxidation of LDL is thought to cause or accelerate atherosclerosis. Several studies have found that eating foods high in quercetin lowers the risk of heart disease, and much of the research documenting the health benefits of green tea is based on the amount of green tea typically drunk in Asian countries—about three cups per day (providing 240–320mg of polyphenols).
Several animal and test tube studies have demonstrated an anticancer effect of polyphenols from green tea. In one of these studies, a polyphenol called catechin from green tea effectively inhibited metastasis (uncontrolled spread) of melanoma (skin cancer) cells. The polyphenols in green tea have also been associated with reduced risk of several types of cancer in humans.
Because of its soothing effect on mucous membranes (including the lining of the mouth) and healing properties, chamomile can be tried for canker sores and other mouth irritations. A strong tea made from chamomile tincture can be swished in the mouth three to four times per day.
Proanthocyanidins (OPCs), a group of flavonoids found in both green and black tea, have been shown to strengthen capillaries.
Chamomile may reduce intestinal cramping and ease the irritation and inflammation associated with diarrhea. Chamomile is typically drunk as a tea; many doctors recommend dissolving 2–3 grams of powdered chamomile or adding 3–5mL of a chamomile liquid extract to hot water and drinking it three or more times per day, between meals. Two to three teaspoons of the dried flowers can be steeped in a cup of hot water, covered, for 10 to 15 minutes as well.
Caffeine is found in black and green tea. While not every study finds that caffeine reduces female fertility, many doctors recommend that women trying to get pregnant avoid caffeine.
In one study, consumption of 3 cups of decaffeinated coffee per day was associated with an increased risk of miscarriage. In another study, caffeine consumption compounded the negative effects of alcohol consumption on female fertility. Some researchers suspect that the tannic acid found in any kind of coffee and black tea may contribute to infertility.
Long-term, complete avoidance of caffeine reduces symptoms of what is commonly called fibrocystic disease. The decrease in breast tenderness can take six months or more to occur after caffeine is eliminated. Breast lumpiness has been reported to not respond well to avoidance of caffeine, but the pain decreases significantly in some women.
Caffeine found in black and green tea, increases stomach acid. Avoiding these substances should therefore aid in the healing of gastritis.
Gastroesophageal reflux disease (GERD)
Acidic beverages, such as tea, have been linked to increased heartburn pain and may contribute to symptoms in people with GERD.
Green tea has been shown to lower total cholesterol levels and to improve the cholesterol profile (decreasing LDL cholesterol and increasing HDL cholesterol). However, not all trials have found that green tea intake lowers lipid levels.
In a study of heavy caffeine users (people who were consuming an average of 560mg of caffeine per day from coffee and tea), changing to decaffeinated coffee and eliminating all other caffeinated products for two weeks resulted in a statistically significant 25% reduction in triglyceride levels.
Although green tea contains a small amount of caffeine, intake of 3 cups or less of green tea daily has been shown not to affect blood triglyceride levels. Intake of four or more cups per day has been correlated with lower triglyceride levels. Overall, the evidence is unclear on how much of an effect high levels of intake of green tea has on triglyceride levels. It is likely that other constituents in green tea compensate for the presence of caffeine in the beverage.
Green tea contains polyphenols with significant antihistamine effects. However, human trials have not studied the effect of green tea or its constituents for the treatment or prevention of hives. Doctors sometimes recommend 3 cups of green tea per day to prevent hives.
Right after consuming caffeine from coffee or tea, blood pressure increases briefly. While the effects of long-term avoidance of caffeine on blood pressure remain unclear, a few reports have even claimed that long-term coffee drinkers tend to have lower blood pressure than do those who avoid coffee. Despite the lack of clarity in published research, many doctors tell people with high blood pressure to avoid consumption of caffeine.
Hibiscus tea (made from Hibiscus sabdariffa) has been reported to reduce blood pressure in people with hypertension. Boil two tablespoons of tea in 1 cup of water for 20 to 30 minutes and consume daily for at least two weeks.
Even modest amounts of caffeine may increase symptoms of hypoglycemia. For this reason, people with low blood sugar should avoid caffeinated beverages, including tea.
While green tea has stimulated production of immune cells and has shown anti-bacterial properties in some studies, more research is needed to evaluate the effectiveness of green tea in protecting against infection.
Chamomile (Matricaria recutita) has been used traditionally to relieve inflamed or irritated mucous membranes of the digestive tract. Since heartburn sometimes involves reflux of stomach acid into the esophagus, the anti-inflammatory properties of chamomile are also useful. In addition, chamomile appears to promote normal digestion. However, modern studies are lacking to prove chamomile beneficial for people with heartburn or indigestion. Roman chamomile (Anthemis nobilis) has not been studied for indigestion, though it has traditionally been used similarly to German chamomile.
Chamomile tea is an old folk remedy for anxiety, particularly when it causes insomnia. Often 1 cup of tea is taken three or more times per day.
Black tea contains tannins that strongly inhibit the absorption of non-heme iron (e.g., iron from non-animal sources). This iron-blocking effect is so strong that drinking black tea can help treat hemochromatosis, a disease of iron overload.
Chamomile essential oils have eased intestinal cramping and irritation in laboratory experiments on animals. Herbalists sometimes recommend chamomile to relieve alternating bouts of diarrhea and constipation, though research has yet to investigate these effects. Chamomile is typically taken three times per day, between meals, in a tea form by dissolving 2–3 grams of powdered chamomile or by adding 3–5mL of herbal extract tincture to hot water.
Increasing dietary oxalate can lead to an increase in urinary oxalate excretion. Increased urinary oxalate increases the risk of stone formation. As a result, most doctors agree that kidney stone formers should reduce their intake of oxalate from food as a way to reduce urinary oxalate. Many foods contain oxalate; however, only a few—including tea—appear to significantly increase urinary oxalate levels.
Drinking caffeine-containing beverages increases urinary calcium levels. Long-term caffeine consumers are reported to have an increased risk of osteoporosis, suggesting that the increase in urinary calcium caused by caffeine consumption may be significant. However, tea consists mostly of water, and increasing water consumption is known to reduce the risk of forming a kidney stone. While many doctors are concerned about the possible negative effects of caffeine consumption in people with a history of kidney stones, preliminary studies in both men and women have found that tea consumption is actually associated with a reduced risk of forming a kidney stone. These reports suggest that the helpful effect of consuming more water by drinking tea may compensate for the theoretically harmful effect that caffeine has in elevating urinary calcium. Therefore, the bulk of current research suggests that it is not important for kidney stone formers to avoid tea.
Like salt, caffeine increases urinary loss of calcium. Caffeine intake has been linked to increased risk of hip fractures, and to a lower bone mass in women who consumed inadequate calcium. Many doctors recommend decreasing caffeinated coffee, black tea, and caffeine-containing soft drinks as a way to improve bone mass.
Curiously, while caffeine-containing tea consumption has been linked to osteoporosis in some studies, others have reported that tea drinkers have a lower risk of osteoporosis than do people who do not drink tea. Possibly, other constituents of tea, such as flavonoids, might override the calcium-depleting effect of caffeine in tea.
Tea drinking can aggravate or interfere with the healing of peptic ulcers in some people.
Chamomile has a soothing effect on inflamed and irritated mucous membranes. It is also high in the flavonoid apigenin. Apigenin inhibits growth of Helicobacter pylori—the organism that causes peptic ulcers—in test tubes. Many doctors recommend drinking 2 to 3 cups of strong chamomile tea each day. The tea can be made by combining 3–5mL of chamomile tincture with hot water or by steeping 2–3 teaspoons of chamomile flowers in the water, covered, for 10 to 15 minutes. Chamomile is also available in capsules; two can be taken three times per day.
In a study of Chinese women, increasing tea consumption was associated with increasing prevalence of PMS. Among a group of college students in the United States, consumption of caffeine-containing beverages was associated with increases in both the prevalence and severity of PMS. The more caffeine women consumed, the more likely they were to suffer from PMS. A preliminary study showed that women with heavy caffeine consumption were more likely to have shorter menstrual periods and shorter cycle length compared with women who did not consume caffeine. Therefore, many doctors recommend that women with PMS avoid caffeine-containing beverages, including tea.
Tooth decay (dental caries)
Compounds present in both green tea and black tea have been shown to inhibit the growth and activity of bacteria associated with tooth decay. Animals given tea compounds in their drinking water develop fewer dental caries than those drinking plain water. Human volunteers rinsing with an alcohol extract of tea leaves before bed each night for four days had significantly less plaque formation, but similar amounts of plaque-causing bacteria compared with those with no treatment. Tea drinking has not yet been tested as a tooth decay preventative in humans.
German doctors practicing herbal medicine have recommended chamomile for people with colitis. A cup of strong chamomile tea drunk three times per day is standard, along with chamomile tea enemas.
Green tea extract rich in polyphenols (epigallocatechin gallate, or EGCG) may support a weight-loss program by increasing energy expenditure. However, clinical trials on weight loss in humans are needed to confirm these preliminary observations. No studies have tested the effect in humans on energy expenditure of drinking brewed tea.
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The information presented in Foodnotes is for informational purposes only and was created by a team of U.S. registered dietitians and food experts. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements, making dietary changes, or before making any changes in prescribed medications. Information expires December 2003.