CHINESE and Japanese tea makers have been right all along. According to German medical scientists, the western habit of mixing milk with a cup of tea is bad for your heart.

Not only that, but there are indications that drinking milk with tea could reduce the body's ability to fight cancer.

Writing in the latest issue of the European Heart Journal, the research team say that they have discovered that the protection tea offers to the cardiovascular system is "totally wiped out" if milk is added. Using groups of tea-drinking volunteers, the researchers found that black tea significantly improves the ability of arteries to relax and expand - but once milk is added the effect is completely blunted.

The researchers, at Berlin's Charité Hospital, say the results should persuade western tea drinkers to reconsider their habit of adding milk.They say what is wrong with milk is a group of proteins called caseins.The caseins were found to interacted with the tea and cause a fall in the tea's concentration of catechins. Catechins are the flavonoids in tea that mainly contribute to its protection against cardiovascular disease.

Senior researcher Dr Verena Stangl, and the hospital's Professor of Cardiology said there was a broad body of evidence indicating that tea exerted antioxidative, anti-inflammatory and vasodilating effects, thereby protecting against cardiovascular diseases. "As worldwide tea consumption is second only to that of water, its beneficial effects represent an important public health issue," Prof Stangl said.

"But, up to now, it's not been known whether adding milk to tea, as widely practised in the UK and some other countries, influences these protective properties. So, we decided to investigate the effects of tea, with and without milk, on endothelial function, because that is a sensitive indicator of what is happening to blood vessels." Sixteen healthy postmenopausal women drank either half a litre of freshly brewed black tea, black tea with 10% skimmed milk, or boiled water (as a control) on three separate occasions under the same conditions. The endothelial function of the brachial artery in the forearm was measured by ultrasound before and two hours after drinking, with measurements being taken every 15 seconds for up to two minutes a time.

According to fellow researcher, Dr Mario Lorenz: "We found that, whereas drinking tea significantly increased the ability of the artery to relax and expand to accommodate increased blood flow compared with drinking water, the addition of milk completely prevents the biological effect.

"To extend our findings to a functional model, we determined vasodilation in rat aortic rings by exposing them to tea on its own and tea with individual milk proteins added, and got the same result."Milk contains a number of different proteins: by testing each one separately, the researchers found that it was the three caseins that accounted for the inhibiting effect, probably by forming complexes with tea catechins.Said Dr Stangl: "The well-established benefits of tea have been described in many studies.

"Our results thus provide a possible explanation for the lack of beneficial effects of tea on the risk of heart disease in the UK, a country where milk is usually added."

She said their findings could also have implications for cancer, against which tea has also been shown to be protective. "Since milk appears to modify the biological activities of tea ingredients, it is likely that the anti-tumour effects of tea could be affected as well. I think it is essential that we re-examine the association between tea consumption and cancer protection, to see if that is the case."

Said Dr Lorenz: "It is important to bear in mind that green tea is almost exclusively drunk without milk. So we are talking only about those countries and regions where black tea is consumed and where milk is added. We certainly don't want to dismiss the consumption of black tea: the results of our study merely attempt to encourage people to consider that, while the addition of milk may improve its taste, it may also lower its health-protective properties."