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Tea and Health


Not only is tea soothing and delicious, but throughout its history, it has been associated with important health benefits. New studies point to evidence that these healing properties have a scientific basis. While all tea is healthy to drink, Green tea contains the highest level of polyphenols (flavonoids), which are known for their antioxidant activity.

Consumption of tea is being studied for its reported benefits on:

  • Enhancing immune function
  • Lowering LDL cholesterol levels
  • Increasing HDL cholesterol levels
  • Reducing blood pressure
  • Thinning the blood, reducing the risk of a heart attack
  • Lowering the risk of stroke
  • Reducing the risk of cancer
  • Boosting longevity
  • Aiding digestion
  • Preventing dental cavities and gingivitis


Much of the focus of modern research is on the effects of three ingredients found in tea:

  • Antioxidants (Polyphenols)
  • Nutrients
  • Caffeine

Antioxidants

Many of the health benefits of drinking tea come from the fact that tea contains high levels of antioxidants called polyphenols or flavonoids. These compounds are most prevalent in green and white teas, but are also present in varying degrees in oolong and black teas. In the processing of black teas another antioxidant is formed - theaflavin. This is weaker than the polyphenols in green teas, but still performs antioxidant activities in laboratory experiments. Polyphenols scavenge cell-damaging free radicals, which are linked with cancer-causing genes and cause LDL cholesterol to form artery-clogging plaque. The polyphenols in tea possess 20 to 30 times the antioxidant potency of vitamins C and E. Antioxidants impair the ability of free radical cells to harm the molecules that make up our bodies.

Nutrients

Tea is a dietary source of important vitamins and minerals. Tea contains carotene, a precursor to vitamin A; thiamine (vitamin B1); riboflavin (vitamin B2); nicotinic acid, pantothenic acid, ascorbic acid (vitamin C), vitamin B6; folic acid; manganese, potassium, and fluoride.

Caffeine

In moderation caffeine can be a benefit - stimulating the metabolism, increasing brain function and alertness. However, the stress of modern life, and the prevalence of coffee and caffeinated colas, has lead people to caffeine overload. The typical cup of coffee has approximately 125-185 milligrams of caffeine; the same size serving of tea, about half that amount. Please remember that these are typical levels: depending on how the tea is prepared, caffeine levels can vary greatly. Caffeine is water soluble, so if you lower the water temperature used, less caffeine will be released. For those of you needing a powerful lift in the morning, try matcha- with this type of powdered tea, you consume the leaf itself, not an infusion of the leaf- as it contains significantly more caffeine. Because caffeine from tea does not take effect for 10-15 minutes, it provides more of a subtle lift - not the rapid jolt in a cup of coffee.

The effect of caffeine is also complemented by another compound found only in tea, theophylline. While caffeine primarily is active in the brain and muscles, theophylline is active in stimulating the respiratory system, heart and kidneys. This corresponds to research that tea is helpful in maintaining a healthy cardiovascular system.

The Process of Decaf

Two processes are used for decaffeinating tea. One, which makes use of the solvent ethyl acetate, retains only 30% of the polyphenols. The other is a preferable, natural process that uses only water and carbon dioxide and is called effervescence. It retains 95% of the polyphenols. Be sure to check labels to see which process was used. If it isn't specified, you'll have to contact the manufacturer to find out.


** Please note that the information on these pages represent findings and opinions obtained from a variety of sources. These are presented for your information only and do not purport to make any health claims. Specific medical advice for any condition must be obtained from a licensed health care practitioner.


Andrew Weil, M.D. Answers Letters on Tea and Health

I just read about white tea and its benefits to oral health. It is also supposed to exceed green tea in antioxidants. What are your thoughts, and where can I buy this tea?

White tea, imported mostly from the Fujian Province of China, is the least processed form of tea - to make it, leaves are simply picked and air-dried. Perhaps for that reason, white tea does have even greater antioxidant activity than green tea, which is produced by picking, heating (steaming or pan firing), and drying the leaves. To make black tea, another step, oxidation, is required. White tea comes from the same plant as black and green tea, Camellia sinensis, and has a delicate taste and pale color. It releases the least amount of caffeine of all three teas, typically from five to 15 milligrams per cup.

I haven't seen any evidence that white tea protects oral health any better than other types of tea, but studies at the University of Illinois College of Dentistry have shown that compounds in black tea can destroy or suppress growth and acid production of cavity-causing bacteria in dental plaque. Black tea also affects an enzyme responsible for converting sugars into the sticky material that plaque uses to adhere to teeth. Furthermore, upon exposure to black tea, the Illinois researchers learned that certain plaque bacteria lose their ability to adhere to others, thereby reducing the total amount of dental plaque that forms on teeth. They also found that rinsing with black tea for 30 seconds, five times in a row (in three-minute intervals), stops plaque bacteria from growing and producing the acid that breaks down teeth and causes cavities, although it might stain your teeth if you do this frequently (white tea is much less likely to cause this problem.) In addition, tea contains fluoride, which may further explain why it helps protect teeth.

Even if white tea works better than black tea to promote oral health, it would be a pretty costly mouthwash. Although widely available in the United States now, it can be more expensive than other types of tea. You can order white tea online from many sources, including one of my favorites, In Pursuit of Tea.

Andrew Weil, M.D.

What is Matcha Tea?

Matcha - literally, "powdered tea" - is a special type of green tea: a precious, jewel-green powder that is whisked with hot water in a bowl to make a frothy beverage of the same name. Preparation of matcha is the focus of the Japanese tea ceremony and has a long association with Zen. Matcha is the only form of tea in which the whole leaf is consumed, and because it is made from top-quality leaves that are treated with great care, it delivers more of the healthful elements of green tea than other forms. A unique, beautiful and richly flavorful drink, matcha gives most people a feeling of well-being. In addition, the simple ritual of preparing it is both enjoyable and meditative.

For matcha, unlike most other forms of green tea, farmers cover the plants with heavy shade cloth for three weeks prior to harvest in May. This causes the new shoots to develop larger, thinner leaves with better flavor and texture. Harvesting is by hand, and only the youngest, smallest leaves are selected for the best quality matcha. Farmers steam the leaves briefly to stop any fermentation, then dry them and pack them in bales for cold storage. Aging deepens the flavor of the tea, which becomes optimum after six months.

Health Benefits of Matcha

In addition to providing trace minerals and vitamins (A, B-complex, C, E, and K), matcha is rich in catechin polyphenols - compounds with high antioxidant activity. These compounds offer protection against many kinds of cancer, help prevent cardiovascular disease and slow the aging process. They also reduce harmful cholesterol in the blood, stabilize blood sugar levels, help reduce high blood pressure and enhance the resistance of the body to many toxins. The most important polyphenol in matcha is EGCG (epigallo-catechin gallate), which is the subject of many medical studies. Matcha has a significant amount of dietary fiber and practically no calories.

Andrew Weil, M.D.

Is Decaf Tea Less Protective?

Is decaffeinated green tea as effective an antioxidant as regular green tea, particularly with regard to cancer prevention? I assume the process of decaffeinating tea makes more changes than just removing caffeine. The health benefits of tea are related to the polyphenols (catechins) it contains. These manage to survive much of the processing that tea undergoes after harvest.

Both green and black tea come from the same plant, Camellia sinensis. To make green tea, the leaves are briefly steamed and then dried. For black tea, the leaves are crushed, piled in heaps and "sweated" (a natural oxidation process that causes the leaves to darken and develop a different aroma and flavor than green tea). Sweating also destroys some of the polyphenols, which is why green tea is more health-protective.

Two processes are used for decaffeinating tea. One, which makes use of the solvent ethyl acetate, retains only 30 percent of the polyphenols. The other is a preferable, natural process that uses only water and carbon dioxide and is called "effervescence." It retains 95 percent of the polyphenols. Be sure to check labels to see which process was used. If it isn't specified, you'll have to contact the manufacturer to find out.

Andrew Weil, M.D.

I recently heard a news report about tea being good for bone density. Is this true? How could tea have an effect on bones?

You heard right. Results of a Chinese study published in the May 2002 issue of the Archives of Internal Medicine showed that men and women who are long-time tea drinkers do seem to have an advantage in terms of bone mineral density over those who don't habitually drink tea. That's not the only recent good news about tea. A study from Harvard Medical School showed that tea drinkers among heart attack patients might survive longer than those who drink something else. Study participants who drank at least 14 cups of tea per week were 44 percent less likely to die than those who didn't drink tea; moderate tea drinkers (those who consumed fewer than 14 cups per week) were 28 percent less likely to die for up to four years than those who didn't drink tea.

The bone density study involved 497 Chinese men and 540 Chinese women over the age of 30 who were asked about how much tea they drink as well as about such lifestyle factors as their ages, physical activity, alcohol consumption, smoking and their intake of coffee, milk and calcium supplements. Of the 1,037 study participants, 48.4 percent were habitual, long-term tea drinkers. The researchers found that those who had been drinking tea habitually for six to 10 years had higher bone mineral density in the lumbar spine, and those who had been drinking tea regularly for more than 10 years had higher bone mineral density in all body sites measured than study participants who didn't drink tea regularly. The findings held true no matter what the type of tea - black, green or oolong. However, the study results would not hold true for herbal teas.

The researchers didn't speculate about how tea may strengthen bones but did point out that it contains high concentrations of caffeine, fluoride, flavonoids and phytoestrogens, all of which may affect bone density. Stay tuned for more information.

The researchers who studied tea consumption in heart attack patients speculated that the flavonoids in tea made the difference. Flavonoids are potent antioxidants, also found in apples and broccoli, which have been shown in previous studies to be protective against heart disease.

As you know, I'm a big fan of green tea, which has been shown to protect against both heart disease and cancer. The two new studies suggest that drinking any type of tea also affords additional health benefits.

Andrew Weil, M.D.

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