Milk Cancels Out Benefits of Black TeaResearchers from Charite Hospital, Universitatsmedizin-Berlin, led by Dr. Verena Stangl had subjects drink freshly brewed black tea, black tea with skim milk, and plain hot water. Ultrasounds then showed that those who drank black tea without milk experienced increased flexibility in their arteries. Those who drank milk with their tea or pain water experienced no benefit.
The researchers believe that the proteins in milk called caseins decrease the amounts of healthy flavonoids, blunting the benefits of tea on blood vessels. According to Strangl,
"Black tea significantly improves the ability of the arteries to relax and expand. But when we added milk, we found the biological effect of tea was completely abolished... If you want to drink tea for its health effects, don't drink it with milk."
It's Not The FatsConceptually this is interesting but I naturally wonder if there is more to it. I previously wrote that saturated fats having an immediate effect on the blood in that the fats cause an immediate inelastic effect on the blood vessels. This finding could conceptually offset the positive elasticity effect of black tea however the above study used skim milk which has very little saturated fat content: .3g per cup as opposed to 5 g per cup of whole milk. Obviously this is probably not a candidate and the researchers are probably right in that it's not the milk fats offsetting the benefits of black tea but the milk proteins.
Regardless on what you think of this finding there are unquestionable benefits of drinking black tea. If you're going to do so you might as well learn to like it straight up; it's better for you.
European Heart Journal, Jan. 9, 2007