Milk Blunts Heart Benefits of Tea by Steven Reinberg, HealthDay News
MONDAY, Jan. 8 -- Plenty of studies have suggested that tea
is a boon for cardiovascular health, but new research has found
that adding milk to your favorite brew negates those benefits.
The culprits in milk is a group of proteins called caseins that
interact with tea, decreasing the concentration of catechin -- the
flavonoids in tea that are responsible for its protective effects
against heart disease, according to the study authors.
"There are a lot of studies that show that tea is protective
against cardiac diseases," said lead researcher Dr. Verena Stangl,
professor of cardiology at the Charite Hospital,
Universitatsmedizin-Berlin, in Germany. "If you look at the
studies, you see that in Asia there are less cardiac diseases, but
in England that's not the case. So the question is, is the addition
of milk a reason for this difference between Asia and England,
where tea is often taken with milk?" she said.
In the study, 16 healthy postmenopausal women drank either half
a liter of freshly brewed black tea, black tea with 10 percent
skimmed milk, or boiled water on three different occasions under
similar conditions. The researchers then measured the function of
the cells lining the brachial artery in the forearm, using high
resolution ultrasound before and two hours after tea
consumption.
Stangl's team found that black tea significantly improved the
ability of the arteries to relax and expand. "But when we added
milk, we found the biological effect of tea was completely
abolished," she said.
Additional experiments on rat aortas and rat endothelial cells
-- which line blood vessels -- found that tea relaxed the vessels.
But adding milk blunted the effect.
"If you want to drink tea for its health effects, don't drink it
with milk," Stangl said.
The study findings are published in the Jan. 9 online edition of
theEuropean Heart Journal.
Stangl noted that not only does milk block tea's benefits for
blood vessels, it also destroys the antioxidant effects of tea and
perhaps its cancer-protective effects as well.
She said her team is also comparing the effects of green and
black tea on the function of blood vessels. "It's a question
whether green tea, with its higher catechin content, is better than
black tea in regard to endothelial function," she said.
One expert agreed that you should hold the milk when drinking
tea.
"This is actually something we tell patients to do -- not to
have milk in tea," said Dr. Robert Vogel, a professor of medicine
at the University of Maryland Medical School.
Tea is one of the greatest sources of antioxidants, Vogel said.
"In countries where they drink a lot of tea, heart disease is
decreased, except for the British Isles. It is typical in Great
Britain to add milk."
Vogel's advice is simple. "Add lemon not milk. You should not
add milk or cream to tea -- it's a very good drink, but not with
milk," he said.
More information
The American Heart Association can tell you more about
lowering your risk for heart disease.
SOURCES: Verena Stangl, M.D., professor of cardiology, Charite
Hospital, Universitatsmedizin-Berlin, Campus Mitte, Germany; Robert
Vogel, M.D., professor, medicine, University of Maryland Medical
School, Baltimore; Jan. 9, 2007,European Heart Journal, online
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