Milk in tea could be preventing weight loss

Scientists have discovered that tea contains high levels of compounds that help to reduce the amount of fat but proteins found in cows' milk neutralise this fat fighting ability Photo: ALAMY

Scientists have discovered that tea contains high levels of compounds that help to reduce the amount of fat absorbed by the gut and can cut cholesterol. However proteins found in cows' milk neutralise this fat fighting ability.

New research has shown that the compounds, called theaflavins and thearubigins, prevent obesity when given to rats that were also on a high-fat diet.

The researchers now believe this could explain why people in Britain appear not to benefit from the healthy affects of tea despite being among the world's biggest consumers of the beverage.

Dr Devajit Borthakur, a scientist the Tea Research Association, in Jorhat, India, said: "When tea is taken with milk, theaflavins and thearubigins form complexes with the milk protein, which causes them to precipitate.

"It means that we don't get the health benefit from these compounds nor from milk protein. Therefore, it is always advised to take tea without milk."

Scientists at the research centre are now working on developing new breeds of tea with higher levels of these compounds, which are known as polyphenols, while also looking for ways of making them less susceptible to being neutralised by milk.

Their research has shown that low doses of ordinary tea extracts reduced the cholesterol levels in rats while also reducing the levels of fatty acids in the animal's blood stream.

A study by scientists in Japan, which is published this month in the journal of Nutrition, reveals that extracts from tea leaves inhibits the absorption of fat in the gut of rats being fed high fat diets.

These rats also had less fat tissue on their bodies and lower fat content in their livers.

Dr Hiroaki Yajima, a scientist with the Kirin Beverage Company in Japan who carried out the Japanese research, said: “Black tea extracts may prevent diet-induced obesity by inhibiting intestinal lipid absorption.”

The fermentation process used to make "black" tea leaves, the most commonly drunk type of tea in the UK, has also been found to boost levels of these fat-fighting compounds compared to green tea, which is unfermented.

The research suggests that despite more attention being paid to the health benefits of green tea, black tea may have greater health-boosting properties which are masked by the tendency to drink it with milk.

British researchers have also found that the type of milk used in a cup of tea can impact on the level of the "healthy" compounds.

Dr Lisa Ryan, a senior lecturer in human nutrition at the Functional Food Centre at Oxford Brookes University, has discovered that skimmed milk decreases the levels of these active compounds far more than whole or semi-skimmed milk.

Her team looked at five different brands of black tea sold in the UK, measuring the activity of antioxidant and polyphenol compounds after adding different types of milk.

She said: "The fat content of milk seems to be buffering the antioxidants and polyphenols. Molecules called caseins bind to the polyphenols and lead to a decrease in their availability for the body and in skimmed milk this happens more.

"Although adding milk does impact on the availability of polyphenols, tea is still a significant source of them."