The Collison Newsletter September 2007

   

      A CUP OF TEA = A CUP OF GOOD HEALTH*

                                       TEA  

BLACK, OOLONG, GREEN, WHITE, ROOIBOS, HERBAL   

 

“Time for a Cuppa” 

A cup of tea is a way of life, a social activity as well as a solo one. It is a means by which we can unwind and relax.

 

Tea consumption is also linked to numerous positive effects on the body, and it is believed to help prevent a wide range of ailments. A hot cup of tea may do more than relax you.

History 

There is archaeological evidence that suggests that tea has been consumed for almost 5,000 years. India and China were the first two countries to cultivate it.

 

In China, black tea is known as red tea, perhaps a more accurate description of the colour of the liquid. The name black tea, however, could alternatively refer to the colour of the oxidized leaves.

 

While green tea usually loses its flavour within a year, black tea retains its flavour for several years. For this reason, black tea has long been an article of trade and, compressed into bricks, it even served as a form of de facto currency in Mongolia, Tibet and Siberia into the 19th century. It was known since the Tang dynasty that black tea, steeped in hot water, could serve as a cloth dye.

 

The tea originally imported into Europe was either green or semi-oxidized. Only in the 19th century did black tea surpass green in popularity.  Although green tea has recently seen a revival due to its purported health benefits, black tea still accounts for over 90 percent of all tea sold in the West.

The expression ‘black tea’ is also used to describe a cup of tea without milk (served black). In Commonwealth nations, black tea is not commonly consumed black, as adding milk is the common practice (that is, ‘white tea’). In this newsletter, ‘black tea’ is just that and, as you will see, ‘white tea’ is something else again.

Today, tea is consumed in greater quantity worldwide than any other beverage except water. 

The Plants 

  • Camellia sinensis is a large shrub, with evergreen leaves, which is native to India and perhaps parts of China and Japan. The shrub has leathery, dark green leaves and fragrant, white flowers. Black, oolong, green and white teas are all made from this plant, but differ in their methods of preparation.
  • Aspalathus linearis, also called ‘red bush’ has a fine needle-like leaf. It is a South African shrub. Rooibos tea is made from this plant.
  • Herbal Teas are not derived from camellia sinensis or aspalathus linearis, but from the leaves, bark, roots, seeds and flowers of other plants. These teas have not been associated with the many healing benefits related to black and green teas, although some herbal teas have special properties in their own right, which are not dealt with in this Newsletter.  

Processing Tea 

  • Black Tea

The majority of tea consumed (90%) is black. Tea, in the wide variety of types, for example Old English, Earl Grey etc, and the multiple brands is black unless clearly indicated otherwise, namely ‘green’, ‘oolong’ or ‘white’.  

Black tea is made from camellia sinensis. 

Black teas go through an oxidative process known as fermentation before the final heating process. The leaf appearance is black. 

After the tea leaves are picked and harvested, they are first inspected and sorted by hand. 

Withering takes place as water evaporates and this can be accelerated by blowing air across the leaves. The leaves are then processed either by ‘crush, tear, curl’ or the orthodox method, either by machine or hand. Hand processing is used for high quality teas.  

Next, the leaves are oxidized under controlled temperature and humidity. This process is also called ‘fermentation’, which is a misnomer since no actual fermentation takes place and it does not produce alcohol. Enzymes oxidize the leaf and it turns brown, just as a tree leaf in autumn changes colour from green to brown. This process is accelerated by increased heat and high humidity. As a result of these conditions, it takes only a few hours to turn green tea into black tea. The level of oxidation determines the quality of the tea.  

The leaves are then dried to arrest the oxidation process. 

Finally, the leaves are sorted into grades according to their sizes (whole leaf, brokens, fannings and dust), usually with the use of sieves, then packed.  

Black tea is the world’s No 1 beverage, hot, cold, flavoured or scented by the addition of different herbs, flowers etc. For example, in Earl Grey, the flavouring is Bergamot, from the citrus Bergemia, the fruit of which looks like a small grapefruit.

There are well in excess of 100 types of teas resulting from the many different flavourings added to the basic tea. An excellent and outstanding website to help you explore these is t2tea.com.au.  

During oxidation (‘fermentation’), the chemical structure of the leaf is altered. This results in the loss of some of the antioxidants. Hence it is believed that green tea, and ideally white tea, are a better choice for health benefits. 

  • Green Tea

Green tea is referred to as non-fermented or unfermented and is primarily produced in China, Japan and Taiwan. It is also called Chinese tea. 

Green tea is also made from camellia sinensis, and is different from black tea due to its method of preparation.  

The young tea leaves are picked, processed by withering, steaming or pan-firing, followed by drying and grading (sifting). Pan-firing over smoke stops the natural enzymes from fermenting the leaf. Thus, green tea has undergone minimal oxidation during processing. The final leaf appearance is green.  

The production of green tea results in physical changes in the leaf (in the appearance) but not in the chemical structure so that the naturally present oils, polyphenols (antioxidants) and vitamins are preserved in greater quantities compared to black tea. 

  • Oolong Tea 

These teas are produced by semi-fermenting green tea leaves. The properties of oolong teas fall between green and black teas.  

  • White Tea 

This is the least processed of all teas. It also is made from camellia sinensis and is considered by connoisseurs to be the ultimate and the apotheosis of tea. 

At the beginning of spring, before the leaves are fully open and still covered by fine white hair, the finest are picked and harvested from the bush. This is only possible for a very limited period – just a few days – in some areas but for two days. 

It undergoes very little processing, similar to green tea and no fermentation. The result is a flavour that is described as floral, light and sweet.  

The minimal processing retains the highest levels of antioxidants. Of the teas made from camellia sinensis, white tea is lowest in caffeine, 10-15 mg per serving, compared to 40mg for black tea and 20mg for green tea. 

It is prepared like green tea. 

  • Rooibos Tea 

These are produced in much the same manner as normal tea. It comes in red (fermented) and green (unfermented) forms.  

Red rooibos is fully fermented, like black tea, and has a clean aromatic flavour similar to a light and sweet black tea.  

Green rooibos is unfermented, and similarly to green tea, it has a higher level of antioxidants. 

It contains no caffeine, and is low in tannin. Thus it is safe for children and indeed can be drunk all day.  

Organic Tea 

This means that no chemicals, pesticides or fertilizers were used in growing the tea. 

Tea Tannins and Tannic Acid 

As already mentioned, polyphenols are part of the flavonoid component of tea. These polyphenols are made up of the tea catechins and their gallates. They used to be referred to as the Tea Tannins. They are the antioxidants in tea. 

The Tea Tannins are not to be confused with Tannic Acid. Tannic acid is used for the tanning of leather and is found in the bark of many plants and in some ferns. Real tea does NOT contain tannic acid, provided only the fresh, tender leaves are harvested and there is no hard wood or bark used.  

The formula for Tea Tannins is C2OH2OO9, while that of Tannic acid is C14H10O9. 

Health Benefits from Tea 

All teas excluding herbal teas, whether black, oolong, green, white or rooibos, are rich in catechin polyphenols. As described above, the less processed the tea (white and green), the more the antioxidants are preserved in greater quantities. Black tea, being the most processed (‘fermented’) has lower levels, but sill a significant amount. Generally, less green tea is used to make a standard cup so, on a per-cup basis, black tea is not significantly inferior to green. Obviously, the strength of the individual cup, whether black or green, is relevant to the amount of catechin polyphenols (or, for that matter, the caffeine) in the brew.  

There are many cathechin polyphenols in tea. Particularly important is epigallocatechin gallate (EGCG), which is a powerful antioxidant.  

Another important one is theaflavin-3-monogallate, an antioxidant with additional anti-cancer properties.  

The antioxidants in two cups of green or black tea equates to the amount found in 6-8 glasses of orange juice.  

Green tea is also rich in flavonoids, which are antioxidant plant compounds that help protect against free radical damage and its complications. (Antioxidants and free radicals are discussed in detail in my December 2006 Newsletter ‘Free Radicals – Antioxidants’). 

Green tea is now readily available and from a health point of view would be the recommended tea. White tea, although the ‘best’, is much less readily available and significantly more expensive.  

The Chinese have known about the medicinal benefits of green tea since ancient times, using it to treat everything from headaches to depression. Green tea has been used as a medicine in China for at least 4,000 years. 

Tea, especially green, has been credited with providing a wide variety of health benefits. Some of these are supported by scientific studies, and some are unproven claims. 

Scientific Studies of Health Benefits 

  • A study by the Tohoku University School of Public Policy in Japan followed over 40,000 Japanese adults, aged 40-79, with no history of cardiovascular disease (stroke, coronary heart disease) or cancer, for 11 years for death from all causes and for up to 7 years for death from a specific cause. Participants who consumed 5 or more cups of tea per day had a 16 percent lower risk of all-cause mortality and a 26 percent lower risk of cardiovascular disease than participants who consumed less than one cup of tea per day. The study was published in the ‘Journal of the American Medical Association’ (September 2006). The authors concluded: “Green tea consumption is associated with reduced mortality due to all causes and due to cardiovascular disease but not with reduced mortality due to cancer”.
  • A study published in the ‘American Journal of Clinical Nutrition’ (February 2006) concluded: “A higher consumption of green tea is associated with a lower prevalence of cognitive impairment in humans”.
  • An article published in the ‘Journal of the American College of Surgeons’ (May 2006) was the result of a review, carried out by researches at Yale University School of Medicine, that looked at more than 100 studies on the health benefits of green tea. There was ‘an Asian Paradox’ – lower rates of heart disease and cancer in Asia despite high rates of cigarette smoking. The high intake of green tea consumed by many Asians each day provides high levels of polyphenols, in particular EGCG, and other antioxidants. The authors indicated that these antioxidants prevent blood platelets from sticking together. They also improve cholesterol levels, being effective in lowering low density Lipoprotein (LDL), the ‘bad’ type. They also prevent the oxidation of LDL cholesterol and thus reduce the build-up of plaque in arteries.
  • Linked to the above study is the following. There is also a ‘French Paradox’ – despite a diet rich in fat, the French have a lower incidence of heart disease than Americans. The answer was found in red wine, which contains resveratrol, a polyphenol (antioxidant) that limits the negative effects of smoking and a fatty diet. In a 1997 study, researchers from the University of Kansas determined that EGCG is twice as powerful as resveratrol. Thus EGCG is a powerful antioxidant which, in addition to the above information, is said to inhibit the growth of cancer cells and can kill cancer cells without harming healthy tissue.
  • “The oral intake of L-Theanine could cause anti-stress effects via the inhibition of cortical (brain) neuron excitation”. This is the conclusion by the authors of a study published in ‘Biological Psychology’ (August 2006). They looked at the modification of the stress response via L-Theanine, a chemical found in green tea.
  • A study, published in the ‘American Journal of Clinical Nutrition’ (January 2005) concluded: “Daily consumption of tea containing 690 mg of catechins (the antioxidants) for a 12 week period reduced body fat, which suggests that the ingestion of catechins might be useful in the prevention and improvement of lifestyle-related disease, mainly obesity.”
  • Double-blind, randomised, placebo-controlled trials are the bench-mark of clinical studies. One such trial was done by the Division of Cardiovascular Medicine, Vanderbilt University Medical Centre in Nashville, Tennessee. 240 adults were given either the theaflavin-enriched green tea extract (in the form of a 375 mg capsule) or a placebo. After 12 weeks, the patients in the tea extract group had significantly less LDL-cholesterol and total cholesterol (16.4% and 11.3% lower than base-line – a significant reduction, p=<0.01) than the placebo group.
  • A study from Cleveland’s Western Reserve University, published in the ‘Proceedings of the National Academy of Sciences’ (April 2005) examined the effects of green tea polyphenols on collagen-induced arthritis in mice, which is similar to rheumatoid arthritis in humans, an autoimmune disease. The mice given the green tea polyphenols were significantly less likely to develop arthritis. 8 of 18 mice receiving the green tea developed arthritis, whereas 17 of 18 mice who did not receive the green tea developed arthritis. The arthritis in the 8 mice who did develop it when treated with green tea polyphenols was less severe than the arthritis in the non-treated group.
  • A German study found that an extract of green tea and hot water, applied externally to the skin for10 minutes, three times a day, could help people with skin damage from radiation therapy (after 16-22 days). 

In summary, published scientific studies have shown green tea to have health benefits by:

  • reducing mortality due to all causes
  • reducing mortality due to cardiovascular disease (heart attack and stroke)
  • possibly helping to prevent cancer
  • reducing cognitive impairment
  • reducing blood platelets sticking together
  • improving cholesterol levels
  • preventing the oxidation of LDL cholesterol
  • causing anti-stress effects
  • reducing body fat
  • protecting against rheumatoid arthritis
  • healing skin damaged by radiation therapy. 

Unproven Claims of Health Benefits 

There have not been fully validated by scientific evidence, so are simply listed below:

  • stopping neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease
  • helping in the treatment of cancer
  • helping in the treatment of multiple sclerosis
  • preventing free radical damage
  • lowering levels of triglycerides
  • increasing levels of high density lipoproteins (HDL) cholesterol, the ‘good’ type
  • helping prevent tooth decay by killing the bacteria that cause dental plaque
  • reducing blood sugar (rat studies) and hence may inhibit diabetic cataracts
  • increasing bone density. 

Are there any Precautions? 

  • Avoid green tea in pregnancy and while breast feeding, as the caffeine may be harmful to the body. (Likewise, do not drink coffee).
  • Caution would be indicated in the presence of severe cardiovascular disease, kidney disease and overactive thyroid.
  • Green tea may interfere with the effects of warfarin (coumadin), an anticoagulant.
  • The antioxidants in green tea help prevent blood platelets from sticking together, and this anticoagulant effect is why surgical patients, where procedures rely on the patients’ blood clotting ability, are to avoid green tea before surgery. 

Are there any Harmful Effects? 

  • Caffeine. To date, the main negative side effects reported are due to the caffeine content. Tea contains less than coffee. The amount in either beverage obviously depends on the strength of the brew. There are approximately 40 mg of caffeine in a cup of black tea, 20 mg in a cup of green tea, 10-15 mg in a cup of white tea and zero mg in a cup of rooibos tea, compared to 120 mg in a cup of instant coffee and up to 200 mg in cup of strong brewed coffee.  

From experience, the caffeine in tea seems to have much less adverse effects than that from coffee, especially the addiction to coffee and the withdrawals experienced when coffee intake is reduced or stopped completely.  

Side-effects from the caffeine include:

  1. insomnia (sleep disturbance)
  2. nervousness
  3. diureses (increased volume of urine)
  4. possible increase in blood pressure and heart rate. 
  • Other side effects reported (rarely) with a large intake of tea, especially in those with sensitive stomachs, include:
    1. heartburn
    2. stomach irritation
    3. loss of appetite
    4. diarrhoea. 

How Many Cups of Tea per Day?

Inevitably, there are conflicting claims. However from the published evidence, at least two cups and up to four to five cups would be a safe plan. Whether more will give added health benefits remains to be determined by further research. 

How to Brew a Cup of Tea 

  • Use the appropriate teapot size for the number of cups you intend to pour, rather than a bigger teapot only partially filled.
  • The best teapot shape is a round-belly teapot, as this shape lets the leaves circulate when the boiling water is poured in. Glass teapots are recommended for herbal teas.
  • A basket infuser is the best alternative to a teapot.
  • The old adage ‘one [teaspoon or teabag] for each person and one for the pot’ is appropriate.
  • If using just a tea cup, use one teaspoon of leaves in a basket infuser, or one teabag.
  • Warm your teapot and/or cup. This really does make a difference and only takes a minute.
  • When boiling the water, just bring it to the boil, do not over-boil, as this drains the water of oxygen.
  • For black tea, put in the loose leaves, infuser or teabags, then add boiling water.
  • Green teas, however, should never be prepared with boiling water (100C). They should be made with water at about 80C (ie not boiling). To achieve this easily, fill the tea cup or tea pot 1/5 with cold water, then 4/5 with boiling water. Then add the loose leaves, infuser or teabags.
  • Allow black and green teas to steep for at least one to two minutes, and no longer than four minutes. Brewing these teas for too long is often the cause of a bitter after-taste. White teas, however, can take up to 10 minutes to reach their optimum flavour, while herbal teas and rooibos teas can be brewed for as long as you wish.
  • Fresh cold milk is acceptable in most black teas. Do not add milk to green, white, rooibos or herbal teas.
  • If you desire sweeter tea, honey is a good choice. A small amount of sugar is acceptable.
  • A teapot should never be washed with detergent; it should simply be rinsed in warm water. 

* Copyright 2007: The Huntly Centre.

   

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