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

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.

Source: Purdue University

Related stories:

Digestive process affects anti-cancer activity of tea in gastrointestinal cells
Increased consumption of teas rich in catechins is associated with reduced risk of stomach, colon and other gastrointestinal cancers. However, the effects of digestion on the anticancer activity of tea catechins have largely been ignored. A study by nutrition researchers at The Ohio State University and Purdue University found that the digestive process could both alter the structure of the tea catechins and their anticancer activity.
Green tea boosts production of detox enzymes, rendering cancerous chemicals harmless
Concentrated chemicals derived from green tea dramatically boosted production of a group of key detoxification enzymes in people with low levels of these beneficial proteins, according to researchers at Arizona Cancer Center.
Green tea may protect the bladder from becoming inflamed
Herbal agents could be used to treat inflammatory bladder diseases, according to a preliminary study that looked at the ability of green tea to protect bladder cells from inflammation. The University of Pittsburgh School of Medicine study, being presented at the annual meeting of the American Urological Association (AUA) in Anaheim, Calif., found that components of green tea protected bladder cells from damage in culture. The study is Abstract 299 in the AUA proceedings.
Researchers warn milk eliminates cardiovascular health benefits of tea
Research published on-line (Tuesday 9 January) in European Heart Journal has found that the protective effect that tea has on the cardiovascular system is totally wiped out by adding milk.
Tea: the New Anti-Aging Beverage?
Tea may be more than a trendy coffee alternative, according to researchers at the Douglas Hospital Research Centre (DHRC). Their findings, published in a recent issue of the European Journal of Neuroscience, suggest that regular consumption of either black or green tea may reduce the risk of age-related degenerative brain disorders such as Alzheimer disease.
Green tea extract boosts exercise endurance 8-24 percent, utilizing fat as energy source
Swimming endurance improvement comes from equivalent of four cups of tea a day over 10 weeks

Now that even baseball players may need to seek new, more natural performance aids, will Japanese green tea sets become standard in dugouts and athletic training tables around the world?
A new study tested the effect of regularly taking green tea extract (GTE) and found that over 10 weeks, endurance exercise performance was boosted up to 24% with 0.5% GTE supplementation, and 8% with 0.2% by-weight addition to food.
MRI spots DCIS in mice
A new magnetic resonance imaging procedure can detect very early breast cancer in mice, including ductal carcinoma in situ (DCIS), a precursor to invasive cancer. Some of the tumors detected were less than 300 microns in diameter, the smallest cancers ever detected by MRI.
Tainted milk crisis hits more global companies
(AP) -- Snackers, beware: Your favorite chocolate or creamy treats might contain milk contaminated with melamine. The list of companies facing potential recalls grew Friday as reports of foods tainted with the industrial chemical melamine, which has been blamed in the deaths of four Chinese infants, spread to a widening range of products.

News discussion:

Medicine & Health news