Whilst increasing attention is now rightly being paid to the health benefits of white and green teas, the virtues of the much more familiar, and still much more common, black tea, should not be neglected. All three are products of the camellia sinensis plant and as such have many common attributes, particularly in their anti-oxidant functions; the difference between them being entirely attributable to the differing methods by which they are produced.



So-called "herbal teas", by contrast, are drinks made from infusions of the leaves of a wide variety of other plants. Although these are often very beneficial to health, they are not "teas" at all in the strict sense, this term being restricted to the products of the camellia sinenis plant, and should be considered separately, probably as a branch of herbal medicine or therapy.

The fresh, ie unprocessed, leaves of the camellia sinensis plant are rich in compounds known as polyphenols, and particularly those of a type known as catechins, which are powerful anti-oxidants. The problem is that these compounds are easily destroyed by the processing that the leaves go through. In the case of black teas the process, known as fermentation, results in the almost complete oxidation of the catechins resulting in a dramatic loss of their anti-oxidant power.

The highly prized white teas, by contrast, are produced by steaming the very young leaves of the camellia sinensis plant, protecting them from this damaging oxidation. Green teas are produced by a similar process of heat treatment, but the older leaves used are not generally as rich in the active ant-oxidant compounds. There is yet another category of teas, known as oolong, which fall somewhere between the green and black varieties by being partially oxidised (fermented).

Whilst conventional medicine continues to insist that the evidence for the health giving benefits of all these teas remains inconclusive, there is in fact ample evidence of the anti-oxidant power of these beverages. For example, a number of respectable studies have concluded that moderate tea consumption (just a few cups day) may reduce the risk of heart disease by around a third, in the case of black tea, and a half in the case of green tea. At least one research report further suggests that tea consumption may help reduce the risk of stroke by as much as two-thirds.

Since heart disease and stroke remain two of the biggest causes of premature death and disability in the affluent Western world, these findings alone would seem to make the regular consumption of tea, and green tea in particular, a worthwhile precaution.

But the benefits don't end there.

Free radical oxidative damage to the lining of the blood vessels is known to be a factor in the development of atherosclerosis (hardening of the arteries) another major cause of life threatening cardiovascular disease. The consumption of black tea has been shown to have a protective effect on the cells lining the blood vessels (the endothelium) and to the extent that this effect is due to anti-oxidant polyphenols, it appears highly likely that tests with green tea would produce results at least as good.

Less conclusively, but interestingly, there is also evidence that the anti-oxidant qualities of the polyphenols in both green and black tea may have a role in combatting both cancer and osteoporosis.

In the case of cancer, such effects have been clearly demonstrated in animals, though the evidence in respect of humans is less clear cut. But to the extent that cancer is a disease of degeneration, the onset of which may be hastened by oxidative damage in cells caused by free radical activity, the anti-oxidant activity of black and green tea can only be of potential benefit.

Similarly, there is observational evidence that bone mass density is positively correlated with tea consumption, which is therefore protective against osteoporosis, possibly because of the drink's anti-oxidant properties, but the causal link is not fully understood.

Despite the familiar reservations of conventional medicine, there appears good evidence for the anti-oxidant qualities of the polyphenols in tea in general, and green tea in particular. But that's not all. Tea is also a good source of some trace minerals, including manganese, which is itself a powerful anti-oxidant. Black tea is a particularly good source, and a convenient way of obtaining this mineral, which is often drastically under supplied in food. In addition to its general anti-oxidant properties, manganese is also known to nutritional therapists as an aid to cardiac and bone health, in relieving the symptoms of diabetes, and in treating certain types of seizure.

The only likely downside to the consumption of significant quantities of tea is that both green and black varieties may contain considerable amounts of caffeine. Strong black tea is also rich in tannin, the acidic substance which also gives the astringent taste to red wines, and which may lead to minor stomach disturbances if overdone This problem does not arise with green tea, however, and both black and green varieties are readily available in decaffeinated form, the latter also in a range of enhanced natural flavours for improved palatability.