It's Tea Time

It's Tea Time
Whether included in a refreshing beverage, weight-loss bar or antioxidant dietary supplement, tea extracts and isolated compounds are hot commodities.

by Heather Granato

Around the globe, tea holds an exalted place among beverages--witness the Japanese tea ceremony, High Tea in England or the use of medicinal brews in China. Next to water, tea is the most consumed beverage in the world. People have been drinking it for centuries, since they discovered the great taste component and then the health aspects of the plant. India and China grow almost half of the world's tea, though they export less than a quarter of their crops due to large domestic demand. While the English still lead the world in per capita consumption (averaging three to four cups of tea per day), the United States is catching up.

The generic term "tea" refers to a class of beverages featuring the leaves of the Camellia sinensis (C. sinensis) plant, herbal components or a combination of both. Actual tea--green, black, white or oolong--is sourced from C. sinensis; the differences between types are dependent on processing, which also contributes to their varying health properties. White and green teas are the least processed, which allows them to retain high levels of bioflavonoids (i.e., catechins). Black and oolong teas are fermented for a set time and then cured. The fermentation produces more complex flavonoids (i.e., theaflavins), which also give black tea its characteristic color and flavor.

Research has shown that both catechins and theaflavins offer equally effective free-radical scavenging abilities.¹ "Teas offer an abundance of polyphenol antioxidants that are being closely examined for their potential contributions to heart health and their apparent effects against chronic diseases," said Grey Shayka, sales representative for Flanders, N.J.-based American Instants Inc.

A research review from Oregon State University, Corvallis, noted the effects of these polyphenols appear promising in reducing oxidative stress.² However, they recommended larger studies in humans to examine the effects of tea and tea catechins on biomarkers of oxidative damage to lipids, protein and DNA.

Companies have offered tea extracts to the dietary supplement and food markets for many years. Ginny Bank, technical director at Blauvelt, N.Y.-based RFI Ingredients, noted the company's OxyPhyte tea products have been popular in liquid and capsule forms. "The high ORAC [oxygen radical absorbance capacity] value of these extracts has made them perfect in antioxidant applications," she said. A preliminary study conducted for RFI at the Health Research Studies Center in Stanford, Calif., found the OxyPhyte Ultra Blend product increased blood ORAC levels by as much as 32 percent after one hour.

Formulators should take care when adding tea extracts for antioxidant potential. "Green tea catechins are highly effective antioxidants, and thus tend to oxidize rapidly in certain conditions," said Scott Smith, senior manager with Edina, Minn.-based Taiyo International. "This is especially true with liquid applications. Care must be taken to avoid unnecessary exposure to light and iron while storing, processing and packaging."

However, the benefits to health are extensively documented. The antioxidant effects of tea extracts, particularly green tea catechins, have been studied in relation to a number of health conditions. Researchers have examined catechins' ability to protect against free radical damage, cell mutation and carcinogen producing enzymes. "Green tea is now accepted as a cancer preventive on the basis of numerous in vitro, in vivo and epidemiological studies," wrote researchers from the Radiation Effects Research Foundation in Hiroshima, Japan, in Aging Research Review.³ "Daily consumption of green tea in sufficient amounts will help to prolong life by avoiding pre-mature death, particularly death caused by cancer."

Most studies have focused on the biological activities of green tea catechins, including epigallocatechin gallate (EGCG), and the ability to affect angiogenesis and apoptosis.⁴ A French study found epigallocatechin (EGC) may trigger breast cancer cell apoptosis,⁵ while Japanese researchers noted green tea prevented tumor initiation in the bladder.⁶ Many companies are offering high-catechin green tea extracts for high-EGCG content; for example, Taiyo's Sunphenon contains 60-percent total catechins, with 30-percent EGCG.

Because it is less processed than green tea, white tea has even higher natural levels of some polyphenols. Studies from Oregon State University have compared activities of green and white teas, and found both to be active in suppression of polyps.⁷ An in vitro study on white tea found it to be a more powerful antimutagen than green tea.⁸ Unpublished follow-up studies found rats fed white tea had fewer pre-cancerous lesions compared to a control group.

Researchers have also compared the antimutagenic activities of green and black tea, and found the protective effects may be the same, though more follow-up is suggested.⁹ In one study at Harvard Medical School, researchers found a combination of black or green tea with soy slowed tumor growth, reduced tumor weight and inhibited metastases.¹⁰ Additional in vitro work showed black tea and its polyphenols had significant antimutagenic¹¹ and antileukemic effects.¹²

Studied along with black and green tea is the newest "tea" on the market--rooibos. Known as red tea, rooibos is sourced from the South African shrub Aspalathus linearis. In a study from the University of Mainz, Germany, green, black and rooibos teas strongly reduced genotoxicity against different mutagens in vitro.¹³ The main flavonoids in rooibos are aspalthin, rutin and orientin.¹⁴ Those flavonoids have been shown to affect immune cells, increasing cytokine generation and augmenting interleukin-2 generation.¹⁵

However, tea's antioxidant effects are not beneficial only in the area of cancer prevention. Heart health is another focal point of research. "There is strong data linking lowered cholesterol by just drinking one to three cups of green tea per day," Bank said. "This combined with its anti-atherogenic properties make it an excellent ingredient for healthy heart formulations."

One recent study found adults who consume high quantities of black tea have a 50-percent lowered risk of coronary heart disease (CHD) compared to non-tea drinkers, independent of risk factors such as smoking or obesity.¹⁶ While the researchers speculated tea's antioxidant polyphenols protected against hypertension or stroke, it is not fully known how tea impacts CHD risk. One clinical study found black tea consumption reduced platelet aggregation in healthy subjects,¹⁷ while researchers studying patients with coronary artery disease and consumed black tea found tea consumption reversed endothelial vasomotor dysfunction.¹⁸ Whether polyphenols prevent lipid peroxidation is still a subject of debate. A recent South Korean study found EGCG was a potent antioxidant in inhibiting ion-induced lipid peroxidation.¹⁹ However, an earlier study of black and green tea extracts did not find consumption inhibited in vivo lipid peroxidation.²⁰

The newest area of health research for tea is in the area of weight loss. Companies are developing specialized green tea extracts to fill a growing need. "The diet and weight-loss applications are growing fast, possibly as a result of the ephedra controversy," said Corey McNeely, national sales manager with Scott City, Mo.-based Creative Compounds. "Green tea is generally perceived as a natural, safe alternative, and the research showing it to be effective in weight loss and appetite suppression couldn't have come at a better time." Creative Compounds recently introduced Catethin green tea extract, standardized for 60-percent EGCG.

A research review from the University of Chicago noted that EGCG influences hormone production, modulates appetite and controls obesity in animals.²¹ One mouse study found those given 2-percent or 4-percent green tea powder in the diet suppressed increases in body weight "remarkably," and the 4-percent diet suppressed appetite.²² The researchers suggested the green tea powder affected lipid metabolism, suppressing fat accumulation. Similarly, Japanese researchers found supplementation with tea catechins stimulated hepatic lipid metabolism.²³

However, it is not only lipid metabolism that is affected by EGCG; it has been suggested EGCG may stimulate thermogenesis as well.²⁴ "Green tea is being used in many diet formulations because of recent clinical studies on EGCG, which is believed to have thermogenic properties," said Larry Martinez, president of City of Industry, Calif.-based Amax NutraSource. "Also, the caffeine in green tea is encased in polyphenols that break down over time, delivering a milder but longer lasting caffeine boost."

A study from the University of Fribourg, Switzerland, underscored the interaction between green tea polyphenols and caffeine.²⁵ The researchers found a green tea extract with both catechin-polyphenols and caffeine augmented and prolonged stimulation of brown adipose tissue thermogenesis to a greater extent than could be attributed to caffeine alone. In fact, tea may contain all the compounds it needs to stimulate and modulate thermogenesis, as one rat study found the amino acid L-theanine (found in green tea) modulated the stimulatory action of caffeine when they were administered together, but theanine alone excited the body.²⁶

"Green tea has become a staple in formulating diet products," said David Garner, executive vice president with New York-based Marco Hi-Tech. "The thermogenic fat burning effect combined with other ingredients that are ephedra substitutes are the 'new wave' of ephedra-free diet formulations. We have built our company platform on providing diet formulation ingredients that are ephedra alternatives."

With the range of health properties it offers, tea is increasingly popping up in product formulations. Generally, it is innocuous in formulations, with a few exceptions. Allan Himmelstein, president of Parsippany, N.J.-based Plantextrakt Inc., noted tea extracts with very high polyphenol content could cloud beverages. "Manufacturers have to decide what the product parameters are--high catechin content, for example--and work with the formulation to meet product needs," he said.

Assistance is available from most ingredient suppliers in formulation. "Manufacturers should look to a qualified supplier to provide help in formulating and masking the undesirable aspects of tea in a beverage or functional food," Martinez said. "Determine which beneficial aspect you are trying to emphasize and then ensure that you have provided efficacious amounts of the extract to achieve that effect so you have a product that works. For example, if you are emphasizing weight loss, provide an efficacious amount of EGCG. For antioxidant effects, provide adequate polyphenols, etc."

Whatever the health benefits, consumers are looking for new ways to support their health with natural compounds. "Consumers are quite aware that teas have health benefits," Bank said. "They may not be aware of exactly what benefits, but since the mindset of 'healthy' is already there, it's easy to go the next step and educate about specific benefits."

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