(24-10-14) Citrus Juice, Vitamin C Give Staying Power To Green Tea Antioxidants

November 14, 2007
Source:
Purdue University
Summary:
To get more out of your next cup of tea, just add juice. Citrus juices enable
more of green tea's unique antioxidants to remain after simulated digestion,
making the pairing even healthier than previously thought.
o get more out of your next cup of tea, just add juice.

A 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, like
reduced risk of cancer, heart attack and stroke. 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.
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.
The study was funded by the National Institutes of Health.
Story Source:
The above story is based on materials provided by Purdue University. Note:
Materials may be edited for content and length.

Source: http://www.sciencedaily.com/releases/2007/11/071113163016.htm

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