How to Boost Green Tea Benefits
Green tea by itself is a potent source of healthy antioxidants
known as catechins. But a new study indicates that adding citrus
juice or vitamin C can significantly boost the bioavailability
of those compounds, which have been linked to lowered cancer risk
as well as improved heart and brain health.
The study by Purdue University researchers, published in the
November 2007 Molecular Nutrition and Food Research, involved
putting green tea alone and with various additives through a model
simulating gastric and small-intestinal digestion. They found
that catechins are unstable in non-acidic environments such as
the intestines and less than 20 percent of the total remains after
digestion. But adding vitamin C (which is done in ready-to-drink
products to increase shelf life) increased recovered levels of
the two most abundant catechins by sixfold and 13-fold, respectively.
Adding citrus juice to plain green tea was also beneficial. The
study found that lemon juice caused a roughly four-fold boost
in the recovered levels of catechins; in order, the next most
effective juice additions were orange, lime and grapefruit. And
one should not be stingy with the juice - while adding 10 percent
juice was helpful, the best catechin preservation happened at
levels of 20 to 50 percent juice. This suggests that while adding
a squeeze of lemon to tea is an excellent idea, it also makes
sense to think in terms of 20 to 50 percent blends using orange
and grapefruit juices.
Studies have shown catechins from the green tea plant, Camellia
sinensis, can inhibit cancer cell activity and stimulate production
of immune-strengthening enzymes.The researchers believe that other
types of tea, such as black or oolong, would likely also benefit
from the addition of juice or vitamin C, because these types also
contain catechins, though in smaller amounts than in green tea.
Dr. Weil's take: This is an interesting study, full of important
implications. First, I am not surprised that adding lemon juice
to tea - a popular combination for centuries - appears to be the
best practice for health, confirming that time-honored culinary
traditions are often ahead of laboratory research. Second, this
appears to be one of the rare cases in which a prepared food product
such as a bottled or canned tea preserved with vitamin C can compete
for health benefits with a fresh, homemade one. Finally, if you
like citrus in your home-brewed tea, by all means, squeeze away!
January 6, 2010