Tea and Your Health

[David Baxter PhD]

The Benefits of Tea
Berkeley Wellness
April 1, 2010

After water, tea is the most commonly consumed beverage in the world. But can it really improve your health, as claimed?

Black, green, oolong and white tea all come from the Camellia sinensis shrub and contain a range of polyphenols, notably flavonoids, which have antioxidant and other biological properties that are thought to help protect against disease. Green teas, for example, are rich in catechins, while black tea contains thearubigens and theaflavins. Various polyphenols may have different biological properties and thus different effects in the body?and so far, no one knows if any type of tea is ?best.?

Here?s a brief look at some of the research:

Heart health: Population studies have linked tea consumption with a reduced risk of cardiovascular disease. Tea may lower LDL (?bad?) cholesterol and make it less susceptible to artery-damaging oxidation, as well as improve blood vessel functioning, lessen inflammation and inhibit blood clotting. But not all studies show heart benefits.

Cancer: In lab studies, tea polyphenols have been shown to inhibit various cancers, including colon, bladder, lung, skin and prostate. Results from human studies, however, are less consistent. Several observational studies in women, for example, have linked tea with reduced risk of ovarian cancer. On the other hand, one review article cited mixed results on tea and lung cancer.

Body weight: There?s some evidence that tea may have a weight-loss effect, though not all studies find this, and any benefit would be modest at best. In a small study a few years ago, oolong and green tea boosted energy expenditure in healthy women. And in a Swiss review, most studies found that green tea reduced body weight and body fat. Tea polyphenols may stimulate energy metabolism and boost fat burning, but part of the effect may also be due to tea?s caffeine.

Bone health: Long-term tea drinkers tend to have greater bone density than non*drinkers, several studies have found. Tea contains fluoride, flavonoids and other compounds that are good for bones.

The brain: Lab studies support the role of tea in aiding cognition. Studies in people, however, are limited. In a Japanese study in 2006, older people who reported drinking as little as four to six cups of green tea a week had a reduced risk of cognitive impairment compared to those who drank less.

Bottom line: Though its effects in the body are not fully understood, tea can be a healthy addition to your diet. And all types have something to offer. Without added sugars or milk, tea has negligible calories. But check the labels on bottled and instant teas, since many have lots of added sugar. If you don?t like caffeine, decaffeinated tea is often available.

 

[David Baxter PhD]

Tea Nutrition: Potent Polyphenols
Berkeley Wellness
January 29, 2016

Our love affair with tea goes back thousands of years. The Chinese were cultivating the tea plant about 4,000 years ago and sometime in the 700s the Japanese discovered it. During the 1600s century, Europeans were introduced to tea for the first time by the Dutch and the Portuguese, who picked it up in their travels to Asia.

Tea soon became an important item of trade. The British took up tea drinking with a passion unequaled by any other European people. Tea soon became England?s national drink, with that country importing about 40,000 pounds of tea in 1699, and as much as 240,000 pounds in 1708. Dutch and English colonists brought tea to the New World, and early settlers in America soon embraced this soothing new beverage.

Though tea is an important Asian tradition, for Westerners the culture of tea is quintessentially British. In England, tea (and teatime) has been elevated to a national institution. As teatime rapidly became a common practice in England, it also evolved into two different customs, created loosely along class lines: Low Tea (afternoon tea) was for the aristocrats and the wealthy, who enjoyed an array of biscuits, little cakes, sweets, and other desserts along with their pots of tea at 4 p.m. High Tea, on the other hand, was usually had by the middle and lower classes, and was served at 5 or 6 p.m. More of an early dinner, it featured substantial foods like meat and vegetables, along with the tea.

In the world at large, the countries with the highest consumption of tea are India and China, who together are responsible for producing 80 percent of the world?s tea. Though the United States consumes quite a few metric tons of tea a year, the per capita consumption is quite low: only 1/2 cup daily.

Tea: nutrition
The fluoride in black, green, or oolong tea may help to strengthen tooth enamel, fight cavities, and prevent dental plaque. However, apart from fluoride, tea contains only a little potassium and folate, and traces of other minerals. Unless you add sugar or honey, tea has just 2 calories per cup.

Green tea is a likely choice these days for people looking for health benefitsfrom their beverages. But current research indicates that all tea is good for you, as long as it comes from the leaf of Camellia sinensis?as do all green, black, and oolong (red) teas.

The chemicals that likely make tea a potential protector of health are called polyphenols. Though green tea was once thought to have the most polyphenols, it turns out that black tea has a similar amount. The most potent polyphenol in tea is a substance called EGCG (epigallocatechin gallate), which belongs to a group of flavonoid phytochemicals called catechins. The polyphenols in tea seem to operate in a variety of ways: They may help halt the damage that free radicals do to cells and inhibit a variety of cancers. Yet studies of these and other antioxidants have yielded contradictory results. These substances can protect against oxidation in a test tube, but in the human body they can have the opposite effect?acting as pro-oxidants as well as antioxidants. Or they may have no effect at all.

While tea may have health benefits, it clearly is no panacea. Think of tea as an adjunct to other good health habits, not as a miraculous potion that will keep you well by itself.

For a full listing of nutrients, see the National Nutrient Database:

• Black tea
• Green tea
• Oolong tea

 

[David Baxter PhD]

Types of Tea: Black, Green, Oolong, and Blends
Berkley Wellness
January 29, 2016

There are over 3,000 varieties of tea grown worldwide, and all of them come from the same type of plant, a small shrub called Camellia sinensis. Each type of tea has certain flavor characteristics associated not only with the variety but also with the soil and climate in which it is grown, much like wine grapes. But beyond the subtle flavor differences from tea to tea, there are three main categories of tea—black, oolong, and green—that are a function of how the tea leaves are processed.

The freshly picked tea leaves (usually the tender leaves from the top of the plant) are dried slightly, then crushed to bring out the essential oils, and finally “fermented.” Though this final stage is called fermentation, it is not the result of an introduced organism, but rather is oxidation caused by a natural enzyme in the tea leaves themselves. This “fermentation” brings out the tannins and oils, which contain caffeine, and changes the color of the tea leaves to brown.

In addition to the broad categories based on fermentation, teas are also identified by a leaf-grading system. For black teas, the grades are: souchong, orange pekoe, and pekoe. For green teas, the leaf grades are: gunpowder and young hyson. There are several other identifiers for types of tea, including classic blends (such as Earl Grey) and districts (such as Darjeeling).

Black teas
Black teas are fully fermented, and because of this, they are also the highest in caffeine. They are also the most popular type of tea in the United States.

• Assam: This is a robust, large-leafed tea from India.
• Ceylon: This Sri Lankan black tea has a floral aroma.
• Darjeeling: From the Darjeeling region of India, this is a favorite of tea connoisseurs, and is probably the world’s most expensive tea. Because it is so costly, many “Darjeelings” are actually blends (though the packaging should say if the tea is 100 percent Darjeeling). Darjeeling also comes as an oolong.
• Keemun: One of the best Chinese black teas, it has a rich bouquet and good flavor.
• Lapsang souchong: This distinctive Chinese black tea has a smoky flavor.
• Ti kuan yin: A sought-after tea, this is available as both a black tea and an oolong. Its name translates as “iron goddess of mercy.”
• Yunnan: From southwest China, this is similar to Ceylon.

Oolong (red) teas
This is the type of tea found in most Chinese restaurants in this country. Like black tea, it is fermented, but for shorter periods of time. Within this category, there are some that are more fermented than others.

• Black dragon: The word “oolong” translates into English as black dragon.
• Cantonese oolongs: These oolong teas from Canton are very lightly fermented.
• Formosa oolongs: These teas are fermented for almost as long as black teas and are the most caffeinated of the oolongs.
• Jade oolong: This lightly fermented tea has overtones of green tea and a delicate flavor.
• Jasmine: This is an oolong that has had night-blooming jasmine blossoms added to it for a floral scent. It is most often made with pouchong oolong.
• Pouchong: This medium oolong is rarely exported to the United States, except in a form scented with jasmine, gardenia, or lychee.

Green teas
Green teas are completely unfermented. The fresh leaves are air-dried and then roasted or steam-dried. This heating process halts the natural enzymatic action that is involved in fermentation. Green teas have almost no caffeine. There are dozens of green teas from China, Korea, and Japan, where green tea is the tea of choice. There are also teas from areas that do not by tradition produce green teas. For example, Sri Lanka and India are now making unfermented versions of their classics, such as Darjeeling green. One of the most famous green teas is Gunpowder from China, named because the loose tealeaves are rolled into gunpowder-colored pellets.

Tea blends
Some of the better-known teas (at least to Westerners) are tea blends, many of them created by British tea companies in honor of members of the royal family, or as private blends for wealthy customers. Though there are hundreds of such blends, a handful have gained worldwide popularity.

• Earl Grey No strict formula defines this—it’s usually a blend of Darjeeling, Ceylon, and Chinese black teas—but it is always flavored with the oil of bergamot (a sour, inedible orange cultivated for its aromatic oils).
• English Breakfast: This is not so much a specific blend as a category of blend, which suggests a mixture of several strong Chinese black teas.
• Irish Breakfast: This is a mix of strong black teas.
• Lady Londonderry: This tea was created by a famous tea company in London for one of its customers. It is a blend of black teas from India, Sri Lanka, and Formosa.
• Prince of Wales: This is a proprietary blend created by the Twinings tea company and is a blend of black teas from south China.

How to choose the best tea
Tea lovers would probably unite in recommending loose tea over tea bags, which are most often made from a grade of tea leaf called fannings or dust—fragments of tea leaf broken off from the larger leaves. These leaf fragments are used in tea bags because they have a greater surface area and brew really quickly. This same increased exposure to air is what makes teabag tea less fragrant than loose tea. In addition, teabag teas are often middle-of-the-road teas with no special character.

How to store tea
Because air and light can diminish the flavor of tea, it should be stored in opaque, airtight containers.

How to prepare tea
Soak tealeaves in boiling water. Use a teabag for simplicity, but loose leaves for better quality. If using loose leaves, first soak the leaves and then strain them out before drinking, or try using a tea ball. Be sure to follow directions on steep time so as to avoid bitterness.Some people add sweeteners to tea, but be conscious of how much you choose to add. Avoid purchasing sweetened teas in supermarkets, as these tend to be full of sugar and end up overwhelming the flavor of the tea itself.

It’s fine to use milk in tea, if you like it. You may have heard that milk “binds” some of the beneficial polyphenols in tea, but this has not been proven to be the case.

Also see Tea Benefits: A Research Wrap-up.

 

[David Baxter PhD]

Tea Benefits: A Research Wrap-Up
Berkeley Wellness
February 07, 2014

Okay tea drinkers, your turn. A few months ago we explored the latest research about coffee, almost all of it positive. Scientists have uncovered a similar array of potential health benefits for tea?the world?s most popular beverage, after water. Green tea has gotten the most buzz, but black may be just as healthful. Should you drink a cup?or two or three?a day?

In December a dozen review papers from the Fifth International Scientific Symposium on Tea and Human Health were published in the American Journal of Clinical Nutrition. These drew largely on the more than 2,000 studies done on tea in the past few years. Here?s a wrap-up of this and other tea research.

Tea types and components
Tea comes from Camellia sinensis, an evergreen shrub native to East and South Asia. (?Herbal teas? are made from other plants and are not true tea.) Tea has been consumed for thousands of years in Asia, where it is an important part of many cultures and has long been associated with health benefits. In China and Japan, in particular, its preparation and presentation have been taken to the level of an art form.

Green tea, popular in Asia, is minimally processed?the leaves are steamed, rolled and dried. Black tea is withered, rolled or crushed, and then ?fermented? (in this case meaning oxidized, or exposed to oxygen) before being dried, which makes it black and stronger in taste. Oolong tea is partly fermented. White tea is harvested in early spring; the young leaves and silvery white buds are just steamed and dried.

Like coffee, cocoa and many plant foods, tea contains hundreds of biologically active chemicals, notably a wide range of flavonoids and other polyphenols, which can be absorbed and used by the body to varying degrees. Accounting for about one-third of the weight of dried tea leaves, polyphenols have antioxidant and other potentially beneficial properties.

The chemical composition of tea depends on the specific botanical variety, how and where it is grown, and how it is processed. Green tea, for example, is rich in catechins, including the potent antioxidant EGCG. In black tea, the catechins convert into other compounds during fermentation. Oolong tea falls between black and green teas in composition. Various polyphenols have different effects in the body.

Other factors affecting tea?s chemistry include its age and how it?s stored, brewed and served. Longer steeping time results in more polyphenols being released, though steeping for more than three minutes or so usually doesn?t increase these compounds significantly. Decaffeinating tea reduces its catechins. Instant and bottled teas generally have lower levels of polyphenols. Some research suggests that adding milk to tea binds catechins and reduces their effects somewhat. Lemon, in contrast, may enhance the body?s absorption of catechins.

Unless it has been decaffeinated, tea averages about 40 milligrams of caffeine per six-ounce cup (versus 100 milligrams in coffee, on average), depending on the type, brewing time, and other factors. Black tea tends to have more caffeine than green.

Teasing apart tea benefits
So can drinking tea actually improve your health? Studies have yielded inconsistent, though mostly positive, results (be prepared to hear this again). Complicating matters is the fact that the constituents of tea vary, as do the cultural and dietary contexts in which it is consumed, which may also have effects on health. That may help explain, for instance, why Asian studies sometimes find certain benefits while Western ones do not, or vice versa. Your genes and even your colonic microflora (the bacteria living in your large intestine) may also help determine what effects tea has in your body.

Here?s a look at some of the research:

• Cardiovascular health. Of all the potential benefits of tea, those involving cardiovascular disease are ?the most promising,? according to Jeffrey Blumberg, Ph.D., professor of nutrition science at Tufts University and chairman of the tea symposium. Many (but not all) observational studies have found that people who consume moderate or high amounts of green or black tea (or flavonoids from all dietary sources) have a reduced risk of cardiovascular disease and, especially, stroke?usually with higher consumption linked to greater benefit. Furthermore, most research has shown that tea can slightly lower LDL (?bad?) cholesterol and blood pressure, as well as improve blood vessel functioning, reduce inflammation, inhibit blood clotting and have other cardiovascular effects. In 2013 a British review of 11 clinical trials concluded that tea seems to improve blood pressure and cholesterol levels, but that longer, better studies are needed to confirm tea?s benefits in terms of cardiovascular disease prevention.
• Cancer. In lab studies, green tea extracts and tea polyphenols have been shown to inhibit a wide variety of cancers; black tea has been less studied. There are many theories as to how tea polyphenols may have anti-cancer effects?for instance, by inducing cell suicide in cancer cells and by inhibiting insulin growth factor (a protein involved with cell proliferation). However, the many human studies looking at the association between tea consumption and various types of cancer?such as breast, colon, prostate, oral, liver, ovarian and lung cancer? have had conflicting results. So farm there is insufficient support for claims that tea can help prevent or treat any cancer.
• Diabetes. Most research has linked green or black tea or compounds in tea (such as catechins) to improved blood sugar control or reduced risk of type 2 diabetes. For instance, a 2012 study in BMJ Open looked at data from 50 countries and found that high consumption of black tea was strongly associated with a reduced diabetes risk. And a 2013 Chinese meta-analysis of clinical trials suggested that green tea helps reduce blood sugar.
• Weight control. There?s some evidence that tea, especially green tea, has a modest weight-loss effect. It?s theorized that tea catechins and caffeine help boost fat burning, at least slightly and temporarily. A 2013 analysis of data from the large National Health and Nutrition Examination Survey linked tea consumption with lower weight and smaller waist size; this was not true of iced tea. But not all studies have found an effect on weight. One reason for the inconsistent findings is that the stimulant effect of caffeine depends largely on whether people are used to it or not; if they consume it regularly, they quickly build up a tolerance. What about concentrated green tea extracts, which are often marketed as diet supplements? A 2012 Cochrane review of 14 clinical trials concluded that they do not cause weight loss in overweight or obese people.
• Brain health and mood. Lab studies support the potential role of tea in improving cognitive function. Studies in people are limited, though. For instance, in a study in Japan in 2006 and one in China in 2008, older people who regularly drank green tea were found to have a reduced risk of cognitive impairment compared to nondrinkers. Tea can increase alertness, thanks largely to its caffeine. It may also help enhance concentration and learning ability because of its theanine (an amino acid), which at the same time promotes relaxation. Of course, the experience of drinking a hot aromatic beverage, along with the associations that come with it, can contribute to the calming effect.
• Parkinson?s disease. A 2008 study in the American Journal of Epidemiology found that people who drank the most black tea?but not green tea?had a much lower risk of Parkinson?s disease than nondrinkers. According to a paper in the Annual Review of Nutrition in 2013, human and lab studies suggest that tea or constituents in it may help protect against Parkinson?s and other neurodegenerative diseases. Coffee seems to be similarly protective.
• Bone health. Lab studies show that tea polyphenols have beneficial effects on factors affecting bone mass and bone strength and thus may help protect against osteoporosis. Bones may also benefit from the fluoride in tea. Most studies of postmenopausal women have linked long-term consumption of tea (usually green and often high intakes) or tea extracts with greater bone density, but there are discrepancies among the results. ?More basic research and human studies are warranted,? the researchers at the symposium concluded.
• Dental health. Researchers have found that tea has antibacterial effects and thus may reduce levels of bacteria that cause cavities and contribute to gum disease. Like bones, teeth may benefit from the fluoride in tea. At least two Japanese studies have linked green tea consumption with a reduced risk of tooth loss.

Tea: drinks or supplements?
Tea?s effects in the body are still not fully understood, but don?t expect it to prevent heart disease, cancer or any other conditions on its own. Moreover, it is just one source of flavonoids and other polyphenols ? fruits and vegetables, wine, coffee and cocoa are others. Nevertheless, tea can be a healthy addition to your daily diet, especially if it takes the place of high-calorie beverages. All types of tea have something to offer, including small amounts of minerals such as potassium. Without added sugar, tea has negligible calories. Check the labels on bottled and instant teas, however, since some are as sugary as soda.

Skip green tea supplements. It?s not known if they have any benefits or, more importantly, are safe. In any case, they vary widely in composition ? ConsumerLab.com found a 15-fold difference in catechin levels in products it tested in 2012. Supplements containing high levels of catechins may interact with medications, and there are continuing concerns about potential liver damage. Some, particularly those marketed for weight loss, may contain very high doses of caffeine.

See also this infographic about the Health Benefits of Tea.