LONDON: That dash of milk in the morning cuppa nullifies all the goodness of the tea.
Studies have shown that drinking green or black tea can be good for you because both types contain an abundance of antioxidants called flavonoids. These improve bloodflow and help to prevent heart disease, and are also thought to protect against some cancers.
But German researchers discovered that adding milk to a cup of black tea counteracts the beneficial effects.
The study, published in the European Heart Journal, found that when black tea is drunk on its own, cardiovascular function improves. But it suggests that certain proteins in milk appear to negate the effect of catechins, the particular flavonoids in tea.
The findings are bad news for manufacturers who have promoted the health properties of the beverage to Australians who add milk as a matter of routine.
The study involved 16 healthy post-menopausal women who were given either 500ml of black tea, black tea with 10 per cent skimmed milk or with extra boiled water as a control. They drank it on three occasions but refrained from drinking tea for four weeks before and after the study. The drink itself was made from 5g of Darjeeling tea leaves brewed for three minutes.
In a healthy artery, blood vessels are able to relax if the bloodflow increases – a process called flow-mediated dilation. The researchers measured FMD levels in the forearm before the tea was drunk and at several intervals afterwards. They wrote: “Black tea significantly improved FMD in humans compared with water, whereas addition of milk completely blunted the effects of tea.”
The culprit in milk appears to be a group of proteins called caseins, which interacted with the tea to decrease the concentration of catechins.
What is more is that the bioavailability of the calcium in the milk is compromised by the caffeine in the tea.
As much as we are told of the miraculous antioxidants in tea, chocolate and red wine, perhaps due to the lack of marketing from less glamourous sources – keep in mind vegetables like the humble carrot or beetroot are packed full of goodies too.