TEA-DRINKERS were urged today to give milk a miss if they want to help their hearts.

Studies have shown that drinking tea can help protect against cardiovascular disease (see Factfile below).

But now researchers believe that adding milk to a favourite cuppa counteracts any beneficial effects.

When black tea is drunk on its own, cardiovascular function improves.

The research, published in the European Heart Journal, involved studying 16 healthy post-menopausal women.

They were given either 500ml of freshly brewed black tea, black tea with 10% skimmed milk or boiled water as a control.

They drank it on three separate occasions but refrained from drinking tea for four weeks both before and after the study.

All the women were given a croissant as a standardised breakfast while they drank the tea.

Brewed

The tea was made from 5g of tea leaves, brewed in the water for three minutes.

In a healthy artery, blood vessels are able to relax if the blood flow increases - called flow-mediated dilation (FMD).

The researchers, from the Charite Hospital, Universitatsmedizin-Berlin in Germany, measured FMD levels in the forearm using ultrasound.

They did this before tea was drunk and at several intervals afterwards.

They said: "Black tea significantly improved FMD in humans compared with water, whereas addition of milk completely blunted the effects of tea."

The authors concluded that "milk counteracts the favourable health effects of tea on vascular function".

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

The study showed that a group of proteins in milk, called caseins, could be to blame for the negative effect.

They are thought to decrease the concentration of catechins, which are flavonoids in tea that are thought to help protect the cardiovascular system.

Evidence

Senior researcher Dr Verena Stangl, professor of cardiology at the hospital, said: "There is a broad body of evidence from experimental and clinical studies indicating that tea exerts 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.

"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 (lining of arteries and blood vessels) function, because that is a sensitive indicator of what is happening to blood vessels."

Dr Mario Lorenz, a molecular biologist who worked on the study, said: "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."

The researchers tested the proteins in milk and found it was caseins that accounted for the inhibiting effect.

Dr Stangl said the findings could also have implications for cancer.

"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."

Black tea

Dr Lorenz added: "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."

The team will now compare the effects of green and black tea on vascular function.

June Davison, cardiac nurse at the British Heart Foundation (BHF), said: "It is difficult to say from this small study the impact of adding a drop of milk to your tea can make.

"However, the study highlights the importance of not just thinking about one food in isolation but the effect of the actual interaction between different foods.

"The tea break is a great British tradition which provides time to relax with a cuppa in hand.

"Leaving milk out of your tea is far less likely to help protect your heart health than other measures, such as taking regular exercise, avoiding smoking and eating a healthy balanced diet."