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Nutrition, Vitamins & Supplements for Seniors
Green Tea Antioxidants Provide Double Whammy When Citrus Added
Catechins, naturally occurring antioxidants in tea, stay available after
digestion
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Purdue
associate professor of food science Mario Ferruzzi finds lemon
juice had the most profound impact. (Purdue Ag Communication
photo/Tom Campbell) |
Nov. 14, 2007 – Many senior citizens are among those who drink green tea
for the reported health benefits, like reduced risk of cancer, heart
attack and stroke. But, a new study suggests you can get even more of a
boost by just adding a little juice to the tea.
The
study found that citrus juices enable more of green tea's unique
antioxidants to remain after simulated digestion, making the pairing
even healthier than previously thought.
The study compared the effect of various beverage additives on catechins,
naturally occurring antioxidants found in tea. Results suggest that
complementing green tea with either citrus juices or vitamin C likely
increases the amount of catechins available for the body to absorb.
"Although these results are preliminary, I think it's encouraging that a
big part of the puzzle comes down to simple chemistry," said Mario
Ferruzzi, assistant professor of food science at Purdue University and
the study's lead author.
Catechins (pronounced KA'-teh-kins), display health-promoting qualities
and may be responsible for some of green tea's reported health benefits.
The problem, Ferruzzi said, is that catechins are relatively unstable in
non-acidic environments, such as the intestines, and less than 20
percent of the total remains after digestion.
"Off the bat you are eliminating a large majority of the catechins from
plain green tea," Ferruzzi said. "We have to address this fact if we
want to improve bodily absorption."
Ferruzzi tested juices, creamers and other additives that are either
commonly added to fresh-brewed tea or used to make ready-to-drink tea
products by putting them through a model simulating gastric and
small-intestinal digestion. Citrus juice increased recovered catechin
levels by more than five times, the study found. Ascorbic acid, or
vitamin C, used to increase shelf life in ready-to-drink products,
increased recovered levels of the two most abundant catechins by sixfold
and 13-fold, respectively.
The study, published this month in Molecular Nutrition and Food
Research, also found that soy, dairy and rice milk appeared to have
moderate stabilizing effects. But Ferruzzi said the result is
misleading; a chemical interaction between milk proteins and tea
catechins apparently helps shelter the complex from degradation, a force
likely overcome by enzymes within a healthy human digestive system.
Lemons and tea go even better together than their popularity might
suggest. Lemon juice caused 80 percent of tea's catechins to remain, the
study found. Following lemon, in terms of stabilizing power, were
orange, lime and grapefruit juices. Ferruzzi said both vitamin C and
citrus juices must interact with catechins to prevent their degradation
in the intestines, although data made it clear that citrus juices have
stabilizing effects beyond what would be predicted solely based on their
vitamin C content.
"If you want more out of your green tea, add some citrus juice to your
cup after brewing or pick a ready-to-drink product formulated with
ascorbic acid," Ferruzzi said.
Ready-to-drink green tea products should optimally contain 100-200 mg of
catechins, but oftentimes do not have sufficient levels of tea extract
since some people do not like green tea's flavor, Ferruzzi said.
Although this study only examined green tea, Ferruzzi said he suspects
that some of the results also could apply to black tea, which is
produced by fermenting green tea. Many prefer black tea's flavor,
although it contains lower total levels of catechins.
Studies have shown catechins from the green tea plant, Camellia sinensis,
are able to detoxify toxic chemicals, inhibit cancer cell activity and
stimulate production of immune-strengthening enzymes. Finding methods to
improve uptake of these catechins may, therefore, be important in
improving health, part of the study's goal, Ferruzzi said.
The study was funded by the National Institutes of Health.
Ferruzzi currently is conducting an in vivo study, or study on a live
organism, to quantify the ability of juices and vitamin C to increase
levels of catechins in the intestines and bloodstream of animals and, by
extension, in humans. He collaborates with the NIH-funded Purdue
Botanicals Research Center on this project.
"This next study is designed to get us past the limitations imposed by
our digestive model, which is really just a simple screening process
that relies on preset physiology parameters," he said. "Human digestion
is a lot more complicated."
To see if juices and vitamin C actually increase catechin absorption,
researchers will have to find out if increased levels of intestinal
catechins translate to higher levels of absorbed catechins in live
animals and humans. They also will need to better document effects upon
catechin metabolism in order to prove, for instance, that increased
levels of absorbed catechins are not leveled off by metabolic factors,
Ferruzzi said.
"This study tells us a lot of interesting things, but it raises many
questions that have yet to be answered," he said.
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