green tea has more vitamin c than black tea

 

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November 13, 2007

Citrus juice, vitamin C give staying power to green tea antioxidants

WEST LAFAYETTE, Ind. - Mario Ferruzzi
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caption below

 

To 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.

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.

Writer: Douglas M. Main, (765) 496-2050, dmain@purdue.edu

Source: Mario Ferruzzi, (765) 494-0625, mferruzz@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
Agriculture News Page

PHOTO CAPTION:
A little juice in your hot tea may increase the amount of tea-derived
antioxidants that your body is able to absorb, said Purdue associate
professor of food science Mario Ferruzzi. His study found lemon juice
had the most profound impact, followed by orange, lime and grapefruit
juices. (Purdue Agricultural Communication photo/Tom Campbell)

A publication-quality photo is available at
http://news.uns.purdue.edu/images/+2007/ferruzzi-tea.jpg

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ABSTRACT

Common Tea Formulations Modulate In Vitro Digestive Recovery of Green
Tea Catechins

Rodney J. Green, Angus S. Murphy, Burkhard Schulz,
Bruce A. Watkins and Mario G. Ferruzzi

Epidemiological evidence suggests a role for tea catechins in
reduction of chronic disease risk. However, stability of catechins
under digestive conditions is poorly understood. The objective of this
study was to characterize the effect of common food additives on
digestive recovery of tea catechins. Green tea water extracts were
formulated in beverages providing 4.5, 18, 23, and 3.5 mg per 100 mL
epicatechin (EC), epigallocatechin (EGC), epigallocatechin-gallate
(EGCG), and epicatechin-gallate (ECG), respectively. Common commercial
beverage additives; citric acid (CA), BHT, EDTA, ascorbic acid (AA),
milk (bovine, soy, and rice), and citrus juice (orange, grapefruit,
lemon, and lime) were formulated into finished tea beverages at
incremental dosages. Samples were then subjected to in vitro digestion
simulating gastric and small intestinal conditions with pre- and
post-digestion catechin profiles assessed by HPLC. Catechin stability
in green tea was poor with less than 20% total catechins remaining
post-digestion. EGC and EGCG were most sensitive with less than10%
recovery. Teas formulated with 50% bovine, soy, and rice milk
increased total catechin recovery significantly to 52, 55, and 69%
respectively. Including 30 mg AA in 250 mL of tea beverage
significantly increased catechin recovery of EGC, EGCG, EC, and ECG to
74, 54, 82, and 45% respectively. Juice preparation resulted in the
highest recovery of any formulation for EGC (81–98%), EGCG (56–76%),
EC (86–95%), and ECG (30–55%). These data provide evidence that tea
consumption practices and formulation factors likely impact catechin
digestive recovery and may result in diverse physiological profiles.

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