Does milk ruin tea?
Latest study suggests that milky tea is just as good for you.
Here's a ray of hope for milky-tea drinkers: new research shows that the quaint British custom of adding milk doesn't ruin the beneficial properties of the traditional drink.
Previous studies have suggested that milk can cancel the antioxidant effects of certain chemicals known as polyphenols, found in black tea. Media headlines warned drinkers not to 'ruin' their tea with milk.
But the latest study, by Janet Kyle and her colleagues at the University of Aberdeen, UK, didn't find any evidence for this effect.
The answer is not definitive says Simon Langley-Evans, from the University of Nottingham, UK. Langley-Evans conducted a similar trial in 2000 yet found that for some, but not all, of his trial subjects milk completely wiped out the antioxidant properties of tea. "The situation is a bit muddy at the moment, and this just adds to the mud," he says of the latest news. What should follow from this work is a larger trial, in which more concrete conclusions can be drawn, he suggests.
Kyle and her colleagues agree.
"The information about the potential benefits of tea is quite contradictory," says Garry Duthrie from the Rowett Research Institute in Aberdeen, who was part of the research team. Their work highlights that epidemiological studies are affected by a number of factors, such as infusion time, which should be taken into account in future experiments, he says.
In this study, six commercially available loose-leaf teas were brewed, and all produced similar amounts of polyphenols over similar timescales. The tea that produced the most of these compounds was chosen to be tested on a group of nine healthy young men, who got to put their feet up with a cuppa or two. Black tea was served first and the sample group's plasma was monitored for levels of certain polyphenols. The same thing was done after adding milk to the tea.
The conclusion was that milk made no difference. In both cases, levels of the monitored polyphenols in the blood rose to similar levels. What did make a difference was the time the tea had been allowed to brew. Unsurprisingly, the longer the brew time, the greater the concentration of polyphenol compounds in the tea. "Infusion time certainly makes a difference," says Duthrie.
Earlier this year, Verena Stangl from the Charité Hospital in Berlin, Germany, published a paper suggesting that milk in tea cancels the relaxing effect that tea has on the arteries — which also seems to contradict the new work.
"The divergent results are difficult to explain," Stangl says. "Tea contains a huge number of different substances," she says. Perhaps the molecules responsible for antioxidant activity and those responsible for relaxing the arteries interact differently with milk, she suggests — and not all are being properly monitored by these experiments.
- Kyle J. A. M., et al. J. Agric. Food Chem., doi:10.1021/jf070351y (2007).
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