In Food Today 15 we looked at some of the potential health benefits of phyto-protectants and plant nutrients present in fruits, vegetables, cereals and beverages. Most of these substances are capable of protecting plants from the stresses and strains of their environment. Now research is showing that we too can get these benefits when including these foods in our diets.

Tea is probably one of the most surprising sources of helpful plant nutrients. With the exception of water, tea is the most widely consumed beverage in the world. Green tea is made from the fresh leaves of the tea plant that are steamed, rolled and dried at high temperatures. Black tea is made by first withering the leaves and then rolling and drying them.

The familiarity of a cup of tea makes it hard to imagine that hidden away inside every sip are substances capable of bolstering our bodies defences to help fight chronic diseases such as heart disease or cancer.

The plant nutrients in tea that have fired the enthusiasm of researchers are called flavonoids. Thousands of flavonoids are distributed throughout the plant world and many have antioxidant functions. This means they are capable of mopping up and deactivating potentially harmful free radicals which, if left to roam the body, may spark chronic health problems such as cardio-vascular diseases, cancer, cataracts, inflammation, arthritis and even Alzheimer's disease. For example evidence from a study in Holland (1) has indicated that people with a measurably higher flavonoid intake have a reduced risk of heart disease compared with those who consume less.

Just one cup of tea supplies around 200mg of flavonoids, many of which are released into the drink within the first minute of brewing. However, shorter brewing time leads to lower flavonoid levels. Having three cups a day over 2 weeks increases the concentration of flavonoids in the blood by 25% and fortunately, its antioxidant effects are not affected by adding milk (2).

Drunk daily throughout the world for centuries, Chinese herbalists have long revered the healing properties of tea, recommending it for a wide variety of ailments ranging from clearing the voice to aiding digestion and relieving water retention. Today, the health benefits seem to be getting the seal of approval from scientists in the west.

What's in a Cup of Tea?

Substance	Special points
Catechins:	Over half of the total catechin content is epigallocatechin gallate which is also known as EGCG. It is 20 times more powerful than vitamin C as an antioxidant.
Thearubigins	A complex flavonoid that develops when leaves of tea are fermented and turn black.
Theaflavins	Also produced during fermentation of the leaves.
Caffeine	Mild stimulant found in tea, a 200ml cup contains an average of 40mg of caffeine compared to 64mg in instant coffee and up to 150mg in brewed coffee.
Tannin	A type of flavonoid that adds flavour, astringency and bitterness to tea, in addition to its antioxidant properties.

References

• Hertog, M.G.L, Kromhout, D., Aravanis, C. et al. (1995) Flavonoid intake and long-term risk of coronary heart disease and cancer in Seven Countries Study. Arch Intern Med 155: 381 - 386
• Van het Hof, H.H., Kivits, G.A.A., Westrate, J.A. and Tijburg, L.B.M. (1988) Bioavailability of catechins from tea: the effect of milk. Eur J Clin Nutr 52:356 - 359

FOOD TODAY 09/1999