& Health

Did you know that camelias & cups of tea have something in common ?  They're related!   Tea is derived from the shrub camellia sinensis, native to Asia but also cultivated in Kenya, Brazil & Argentina.

People have been drinking it since 3,000 BC !

Tea is manufactured from the top buds and two younger shoots of a plant, and there are two main types:
 

1. Green Tea,  which is used mainly in Asia, is unfermented.   Steaming or pan-drying are carried out to prevent fermentation, followed by rolling and drying.  The final moisture content is about 2%.

2. Black Tea, the “Western” tea, is fermented, and is made by withering to reduce moisture content, followed by rolling, cutting, fermenting, drying, grading, tasting and blending.

What “makes” tea?   Tea has many chemical constituents.   These include manganese, caffeine (2.3%, approximately half that of coffee), fluoride, folic acid (10%), tannin, ascorbic acid (Vitamin C), salicylates (concentration varying with the variety and season), ash (3% - 6%), protein (2% - 4%), amino acids (2% - 4%), carbohydrates (3% - 4%), lipids (1% - 2%), organic acids (3% - 6%), and polyphenols (9% - 16%).

It’s the polyphenols which are currently exciting interest as far as health is concerned. These contain gallic acid, flavonoids, catechins (richer in green tea), flavonols such as quercetin, and condensed tannins (theoflavins and theorubigens).  The health benefits of polyphenols may lie in their strong antioxidant properties.    82% of antioxidants in the U.S. diet come from polyphenols, of which 25% are from tea.   Incidentally, 80% of tea drunk in the U.S.A. is iced!

Apart from its antioxidant effect, tea is an enzyme inducer, detoxifier and chelator, and has an effect on blood clotting.

The two main areas in which tea is being researched are the prevention of cardiovascular disease and cancer; so much so that green tea tablets (containing 150 mg tea extract, equivalent to 1 cup of tea) are being trialled in Japan and the U.S.    At the recent International Symposium on Tea and Health in Sydney, which I attended, one of the most exciting prospects announced was the possibility that tea may inhibit metastasis (spreading) of malignant melanoma cells.

Metabolism is affected by tea, and this may be protective against breast cancer.   Tea reduces the many mutagenic compounds (heterocyclic amines) formed when frying meat or fish. In this respect, decaffeinated tea may be even more effective. Other cancers which may be inhibited or delayed include oesophageal, stomach, colon, liver, lung, pancreas, bladder and skin.  Japanese researchers have produced the first evidence that cancer onset in patients who have habitually consumed over 10 cups of green tea daily is 7.3 years later (in females) and 3.2 years later (in males) than among those consuming less than three cups per day.   Of course, all very hot fluids add to the risk of cancer of the oesophagus – so let it cool a little.

The benefits of tea seem to be affected by genetic makeup:  some people are better helped than others – for example, in  blood clotting.   Future research will no doubt tell who benefits most.

It was thought, until very recently, that the addition of milk may negate some of tea’s health advantages.   However, we now think the trial which revealed this may have been an aberration due to the occupation of those trialled - mostly Welsh miners.   The consensus at the recent international seminar was that milk made no difference to tea’s health properties.

Tea may help cardiovascular disease by lowering serum cholesterol but increasing HDL (the ‘good’ cholesterol).   Catechins may lower cholesterol absorption.  The antioxidant effect may prevent oxidation, which  LDL (the ‘bad’ cholesterol) needs to block our arteries.   Salicylates and folic acid (folates) may also have a protective effect.   Tea extract increases beta carotene (a strong antioxidant, and Vitamin A precursor in the plasma). Tea also inhibits platelet aggregation, thus protecting against stroke and coronary artery disease [CHD], and it may act against inflammation.

We should not forget the ‘immediate’ effects of tea, which are not all good.   Caffeine is the main culprit (see our earlier newsletter), although less pronounced than in coffee.  Tea does increase skin temperature more than coffee, independent of caffeine – possibly due to its flavonoids – and this causes no harm. Alertness, and cognitive and psychomotor performance, are all increased for about 40 minutes after drinking tea.  But high levels of caffeine may cause nervousness, irritability, and delayed sleep onset.   Tea also acts as a diuretic.  Its absorption ‘half’ life is about eight minutes, and its elimination half life is 3 ½ hours.     Tea may help stress but this may only be due to ‘sitting down in a comfortable chair and taking time to enjoy a nice cuppa’!

It should also be noted that tea interferes with iron absorption.   Thus children and menstruating women in particular should be careful to drink it only between meals, when it will not have this effect.

Mention should be made of herbal teas which, of course, are not really a tea product in the sense described.  Many can be toxic:  e.g., kava plant tea, comfrey, sassafras and ragwort teas.    Others may be beneficial and enjoyable, although insufficient research has been done at this point.

In summary, it seems that tea – like most plant foods – is beneficial to health, that it should be started early in life, and that the optimum intake may be 4 to 10 cups per day, depending on the cup size and the drawing time.