Tea is good for the heart - but adding milk to it wipes out the benefits, say researchers
Tea drinkers enjoy some protection against heart disease. But the benefits are completely wiped out if, like most of the British population, they add milk, researchers reveal today.
Tea has long been thought to have health benefits for the heart and in the prevention of cancer. But researchers from Germany, writing in the European Heart Journal, suggest that their findings about milk ought to lead to an urgent reassessment of the effect of tea on cancer prevention.
"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," said one of the authors, Verena Stangl, professor of cardiology at the Charité hospital, Berlin.
"It is essential that we re-examine the association between tea consumption and cancer protection to see if that is the case."
The team suggests that tea drinkers who usually add milk should drink it black for some of the time. Flavonoids in tea, called catechins, are thought to be responsible for its beneficial effects on the heart. The study found that a group of proteins in milk, called caseins, interacted with the tea to reduce the concentration of catechins.
The researchers measured the effects of drinking black tea, tea with milk and plain hot water on 16 women volunteers. Regular tests on the brachial artery of the forearm for two hours after drinking showed that black tea promoted dilation of the blood vessels. "We found that ... the addition of milk completely prevents the biological effect," said the lead author, Mario Lorenz, a molecular biologist.
Further tests in rats produced the same results. It could explain why Britain, a nation of tea drinkers, does not appear to enjoy protection from high rates of heart disease, say the authors.
"The well-established benefits of tea have been described in many studies," said Prof Stangl.
"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."
June Davison, cardiac nurse at the British Heart Foundation, said the study highlighted the importance of looking at interactions between foods, but added that having a cup of tea could be helpful if it allowed people to relax.
"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," she said.
Source - https://www.theguardian.com/science/2007/jan/09/medicalresearch.medicineandhealth