New research shows that a drop of humble Rosie Lee can help fight off heart disease, cancer and strokes. Put the kettle on, someone

The British desire for a cup of tea, any time of day, is a standing joke abroad. But the growing number of health benefits attributed to drinking it, and the large variety of teas now available, have ensured that it has held its own in the nation's diet despite the recent coffee boom.

The British desire for a cup of tea, any time of day, is a standing joke abroad. But the growing number of health benefits attributed to drinking it, and the large variety of teas now available, have ensured that it has held its own in the nation's diet despite the recent coffee boom.

The celebrity flirtation with exotic herbal elixirs that promise to remove your hangovers, help you to have a good night's sleep, or remove stress toxins in your body, has also given tea the image of being essential for general wellbeing. A range of stars, including Gwyneth Paltrow, Winona Ryder, Julia Roberts and Jennifer Aniston, have espoused the virtues ofherbal blends that promise to ease every state of mind, body and soul imaginable.

While the benefits of exotic herbal teas are largely unproven, recent research into the good old-fashioned cup of char has shown some real benefits, such as reducing heart disease by 44 per cent and diminishing the risk of pancreatic, prostate, stomach and lung cancer. The benefits are believed to derive from a range of vitamins, minerals and antioxidants that lead to good nutrition balance and have anti-ageing properties. A bonus is that drinking a lot of tea increases fluid intake, combating conditions, such as constipation and cystitis, caused or exacerbated by low fluid intake.

The average Briton drinks three and a half cups of tea a day, nearly double the average intake of coffee. Professor Vincent Marks, Dean of Medicine at the University of Surrey, advocates drinking even more tea. "Increasing this average consumption by just one cup per day may yield significant health benefits ... not least because of its contribution to fluid intake," he says.

There are two main forms of tea; black tea, popular in the Western world, and green tea, which is mainly drunk in China, Japan and parts of South America. Both forms come from the same plant, Camelia sinensis, a tropical evergreen indigenous to China and India. Black tea is made from leaf tips which have been withered, rolled and then dried. The nutritional content depends on how much milk and sugar is added. Black tea has virtually no calories. A cup with milk has 23, and two spoons of sugar supply an additional 63. Green tea is produced from fresh tips, where the leaves are not withered and rolled prior to drying. Like black tea, it is rich in antioxidants, but it contains less caffeine and tannin.

The question of whether tea has health benefits has increasingly become a focus for scientific research, with more than 700 studies published last year alone.

The benefits to general wellbeing of black or green tea derive from the fact that they are a rich source of potassium and manganese, as well as vitamins such as vitamin A, which has protective properties, vitamin B6, a crucial part of the body's metabolism, and vitamin B1 and B2, which are essential for releasing energy from food. Potassium is vital for maintaining a normal heartbeat, enables nerves and muscles to function, and regulates fluid levels within cells. Manganese is essential for bone growth and overall body development, and five to six cups of tea produce 45 per cent of our daily requirement.

Tea's direct medical benefits are thought to be due to the presence of a rich source of antioxidants called flavanoids - naturally occurring chemicals that are believed to neutralise "free radicals" and toxins (caused by pollution, smoking and sunlight) that may contribute to heart disease, cancer and strokes. Our daily cup of tea is so full of flavanoids that it is thought to be better at fighting heart disease and cancer than regular intakes of most fresh fruit and vegetables.

Japanese researchers first noted that people living in areas where green tea was grown were only a fifth as likely to develop cancer as those in tea-less areas. Epidemiological research has since shown that Japanese men drinking more than 10 cups of green tea a day are less likely to get lung, liver, colon and stomach cancer.

A study by the Chinese Academy of Preventative Medicine in Peking in 1998 revealed the protective effects of tea: tests found that both black and green tea restricted the development of lung tumours and colon cancer, as well as decreasing the risk of digestive-tract cancer. A more recent study, published in the Journal of Nutrition and Cancer, suggested tea may protect against pancreatic and prostate cancer - the second biggest killer cancer in Britain.

A large number of studies have provided evidence that tea may also help to cut the risk of heart disease, as it reduces cholesterol levels and high blood pressure. One study by American researchers, reported in The Lancet, showed that those who drank at least one cup of tea a day were 44 per cent less likely to suffer a recurring heart attack than those who did not. The researchers suggested that this may be attributed to the high concentration of flavanoids, which reduce blood clotting and cholesterol deposits in blood vessels.

Dr Michael Gaziano, of the Massachusetts Veterans' Epidemiology Research and Information Centre, Boston, who conducted the research, said people should not put sugar in their tea as it could neutralise the benefits of the flavanoids. He said that adding milk or lemon made no difference to the findings, despite previous evidence that adding milk to tea may slightly reduce its antioxidant benefits.

The main problem with drinking a lot of tea is that it may reduce the amount of iron absorbed from food. To absorb the right level of iron, nutritionists recommend that people, particularly vegetarians, should avoid drinking tea with iron-rich foods such as fortified cereals.

It is now possible to buy a large variety of black and green teas. Among the most popular is tuocha tea with ginseng, made from the giant tuocha tea plant grown in the Yunnan region of China. This pure black tea is believed to break down fats and cholesterol; with added ginseng, it is said to aid resistance to disease and help combat tiredness. Herbal infusions have also grown in popularity, although their medicinal properties tend to be historic rather than scientific. Sage tea is said to be good for sore throats and menopausal problems such as hot flushes, while rose-petal and lemon-balm tea is said to work wonders for lifting the spirit. Camomile is said to help you to unwind and to aid sleep, while apple and ginger tea is supposed to relieve both travel and morning sickness.

Researchers from the University of the Orange Free State, South Africa, have verified the anti-ageing claims of the redbush or rooibos herbal tea, which has been used medicinally in South Africa for centuries. The researchers found that it was extremely rich in a flavanoid, aspalathin, that increases the body's own antioxidant enzymes, neutralising age-accelerating free radicals. It also contains quercetin, a natural anti-histamine that makes it good for soothing itchy skin conditions.

But, as Professor Mike Lean, head of the Plant Products and Health Research Group at Glasgow University, points out, the greatest benefit of ordinary black tea is its sheer familiarity: "Tea is very accessible and well liked by a lot of people, so it is an ideal way of helping to reduce heart disease, particularly for people who do not eat a lot of vegetables."