Beyond the Brewed Cup

The advent of research on phytochemicals and health has pushed tea to the front line of disease-fighting foods, and consumers are welcoming various forms and flavors of tea in a wide range of supplements, beverages and foods.

Any herb or herbal blend steeped in boiling water has become known as tea, but true, traditional tea is from the Camellia plant genus, an evergreen plant found mostly in India (assamica) and China (sinensis). How the plant’s leaves are prepared determines the classification— black, oolong, green or white. Leaves picked then left to wither and ferment/oxidize become black tea; leaves subjected to only partial fermentation/oxidation become oolong tea; leaves picked and immediately steamed and double-fired (no oxidation) become green tea; while leaves and the first silvery buds picked and dried without firing become white tea.

As with any botanical, tea is affected by soil properties, growing altitude and weather. This creates many varieties of tea within the same color classification. For example, black teas grown in India (Assam, Darjeeling) have flavor profiles different from black teas grown in Sri Lanka (Ceylon) and China (Yunnan). As if these geographic varieties were not diverse enough, tea artisans long ago added subtle flavorings to create even more distinctive teas—bergamot oil added to Chinese black tea makes Earl Grey, and jasmine flowers added to green tea make jasmine green tea. Combining geographic varieties of the same class of tea was also practiced, as in blending Assam and Ceylon teas to make Irish and English breakfast teas.

With so many detailed geographic, climatic and processing factors involved in distinguishing one tea product from another, the trade and market for tea grew complex and creative. But, tea masters had not yet begun to innovate, as relatively modern creativity gave birth to ice cubes in tea (iced tea) and tea samples in permeable bags. Reflecting the broad frontier still ahead for tea, research over the last century into the health benefits of various teas has unveiled a new world of healthy phytonutrients, stimulating an exploration of functional uses of tea extracts and flavors in dietary products.

To defend against photosynthetic stressors, tea plants developed phytochemicals called polyphenols. More than 90 percent of these polyphenols are flavonoids, which have significant antioxidant properties and have been given the most credit for tea’s health activity. Catechins, theaflavins, tannins and quercetin are considered the most active flavonoids in tea leaves.

It is argued among experts that flavonoid profile and strength are dependent upon the tea’s variety and preparation. Fresh tea leaves contain more simple flavonoids such as catechins. Using the buds and youngest leaves makes white tea the richest source of catechins, while the slightly more mature leaves used in green tea also have a high catechin content. When leaves are oxidized, certain enzymes cause the catechins to form more complex flavonoids such as theaflavins and thearubigins. Fully oxidized black tea leaves have a high content of theaflavins, while partially oxidized oolong leaves have a mixture of catechins and theaflavins. Conversely, flavonols including quercetin, kaempferol and myricitin do not appear affected by processing and are found in equal amounts in oxidized and non-oxidized teas.

Tea rich in flavonoids has been scientifically demonstrated to benefit certain conditions and diseases, including heart disease, cancer, diabetes, kidney stones, Alzheimer’s and Parkinson’s diseases, prostatis, arthritis and HIV infection. In most trials, subjects consumed brewed tea, but as scientists more confidently focus on tea polyphenols, studies appear to use doses of certain flavonoids, including theaflavins, epigallacatechin gallate (EGCG) and similarly named sibling catechins.

At first, epidemiological research pointed to decreased risk and incidence of coronary heart disease (CHD) and cancer, findings that correlated with certain populations known to regularly consume high amounts of tea, such as Asian and Indian populations.^1,2 Though they arrived later to the tea party, Americans have also felt the protective benefit from tea consumption on cancer.³ Delving further, researchers began to pinpoint the actions of tea on these diseases.

A Taiwanese study revealed habitual consumption of green or oolong tea for more than one year significantly reduced the risk of developing hypertension.⁴ Green tea was also found to lower total serum cholesterol⁵ and prevent low-density lipoprotein (LDL) oxidation, thereby lowering the risk of CHD.⁶ The attention soon concentrated on tea’s flavonoid content, as EGCG and fellow catechin EGC were credited with inhibition of cholesterol oxidation in LDL by protecting lipids from certain free radicals.⁷ Black tea and its theaflavins showed similar action, reducing LDL in hypercholesterolemic adults.^8,9 Overall, evidence seemed to demonstrate tea consumption could improve antioxidant status and protect against oxidative damage to lipids and DNA.¹⁰

For patients with CHD, tea has been found to decrease mortality,¹¹ especially from heart attack.¹² Tea flavonoids also exhibit numerous benefits to endothelial function and arterial health. Short- and long-term consumption of black and green tea was found to reverse endothelial vasomotor dysfunction in patients with CHD.¹³ EGCG reduced adhesion of leukocytes to vascular endothelium,¹⁴ in addition to improving circulation and reducing evolving atherosclerotic plaques.¹⁵

Antioxidant function highlights tea’s action against cancer. On the immune health front, tea catechins can halt oxygen free radicals before cell damage can occur,¹⁶ inhibit the growth of tumor cells,¹⁷ and reduce the incidence and size of chemically induced tumors.¹⁸ Emerging polyphenolic phenom white tea has displayed similar anticancer qualities, as researchers from the Linus Pauling Institute found white tea to be higher in polyphenolic content and a more powerful anti-mutagen than green tea.¹⁹

The study of tea against cancer has pinpointed certain cancers. High intake of concentrated green tea catechins severely reduced the rate of prostate cancer development in men at high risk for the disease.²⁰ Tea flavonoids exhibited similar chemoprevention against skin melanoma.²¹ Specifically, catechins EGC and EGCG caused apoptosis of melanoma cells,²² while theaflavins halted the process of skin tumor production.²³ Likewise, flavonoids from both green and black teas arrested liver cancer development and growth,²⁴ and tea catechins promoted apoptosis and limited growth of human cervical cancer.²⁵ Meanwhile, white tea has flexed its catechin muscle against colorectal cancer, limiting formation of pre-cancerous lesions in the colons of animals treated with certain carcinogens.²⁶ Researchers concluded white tea and its EGCG catechins inhibit mutative activity of the protein-gene pathway of beta catenin and Tcf-4, which is involved in development of colorectal cancer, as well as prostate, breast, ovarian and liver cancers.²⁷

Diabetes has also buckled under the strength of tea flavonoids, which may prevent disease onset by protecting pancreatic cells from free radical damage while preserving insulin-producing beta cells.²⁸ Tea also possesses glucose-lowering effects.²⁹ Green tea ameliorated insulin resistance in rats³⁰ and promoted glucose metabolism in both mice and humans.³¹

Even cognitive function is boosted by tea flavonoids. Long-term intake of catechins found in green tea can prevent cerebral atrophy and cognitive dysfunction associated with aging.³² Catechins also can prevent oxidative DNA damage during the early stages of brain atrophy, while EGCG protected the hippocampus from harmful amyloid beta protein and oxidation in one study.³³ However, the antioxidant action alone may not be the sole cause of tea’s benefit to cognitive function. Researchers have theorized the neuroprotective effects by catechins may be due to a combination of iron chelation, scavenging of radicals, activation of survival genes and cell signaling pathways, and regulation of both mitochondrial function and the ubiquitin-proteasome system.³⁴ It is this robust activity that suggested tea catechins could be protective against Alzheimer’s and Parkinson’s diseases.³⁵

One of the most recent and anticipated avenues of health research involving tea is on energy and weight loss. Tea catechins promote weight loss by inhibiting the enzymatic activity that can lead to fat storage,³⁶ as well as by affecting lipid activity. According to one trial, supplementation with tea catechins resulted in a significant reduction of high-fat, diet-induced body weight gain, visceral and liver fat accumulation, and the development of hyperinsulinemia and hyperleptinemia.³⁷ The latest research has shown green tea extract can boost endurance and burn fat in exercising animals, attributing the benefit to EGCG.³⁸ In 2005, scientists in Japan connected tea’s LDLlowering effects with improvements to certain weight management parameters.³⁹ Men taking 690 mg/d of catechins from green and oolong teas experienced reductions in body weight, body mass index (BMI), waist circumference, body fat mass and subcutaneous fat area, as well as improvements to LDL.

As a beverage, tea has experienced recent increases in worldwide consumption, especially as bottled iced tea. Much of this is due to an explosion of gourmet tea blends as well as the wealth of researched health benefits of tea consumption. However, many of the positive studies involved extracts or concentrated intake of specific flavonoids, which has led the industry to expand into offering various forms of tea as supplements. Many companies now supply tea as powders or liquids, often standardizing to or guaranteeing certain levels of flavonoids.

Green tea has enjoyed a lion’s share of tea research and, therefore, many companies offer a range of green tea ingredients.The real innovation and expansion is coming from the introduction of ingredients from other tea varieties, especially in the form of isolated polyphenolic content.

Nashai Biotech Inc. focused on theaflavins because of their demonstrated ability to lower LDL cholesterol in people with mildly to moderately high cholesterol. The company’s TeaFlavin® combines the well-researched catechins from green tea with the increasingly researched theaflavins from black tea. According to the company, TeaFlavin provides 35 times the amount of theaflavins as does one cup of black tea. The product is patented for use in heart health and has an eye on the expanding market. “We have introduced this product into the dietary supplement world in the form of a softgel,” said James Zhao, Ph.D., chief scientific officer. “However we think the bigger market will be beverages, food bars and cereals.” He noted licensing deals with other companies might bring such innovative products to market. In fact, the company has looked into using TeaFlavin to fortify beverages, such as traditional coffee and tea.

On the surge of research into its supreme catechin content and associated health benefits, white tea is garnering increased attention as a functional ingredient. “Recently, white tea has been a very hot ingredient,” confirmed Ellen Schutt, vice president of marketing for RFI Ingredients. “There were innumerable ready-to-drink white tea products introduced last year, and the awareness of white tea continues to grow.” RFI added white tea extract to its OxyPhyte® line of high antioxidant products. Tests have shown this white tea extract has a level of 10,000 to 12,000 ORAC (oxygen radical absorbance capacity) units, more than half of the average ORAC units found in the daily recommended intake fruits and vegetables. This antioxidant capability is why many RFI customers use OxyPhyte white tea, according to Schutt, who reported the extract can be found in supplement products, including ORAC formulations, as well as in functional beverages and drink mixes. She also speculated customers are drawn to white tea because of its unique status among teas.

Despite all the research, some functional product manufacturers choose tea extracts for their flavor. Flavor maven Virginia Dare offers liquids, powders and concentrates of various teas, including white tea and macha green tea. Maureen Draganchuk, vice president of business development, said such flavors are ideal in beverages, nutrition bars and even confections, including ice cream. As functional products manufacturers increasingly use highly polyphenolic tea solids, which are often dried to the point of destroyed flavor, tea flavor extracts and concentrates represent viable complements that can reintroduce that fresh brewed flavor to an otherwise flavorless product.

Another recent innovation in the tea industry is the emergence of Ltheanine, an amino acid found abundantly in green tea. Taiyo International of Japan has patented Suntheanine® in the United States as a dietary ingredient for use in supplements. In Japan, where functional tea products comprise a broad range of foods and beverages, Suntheanine, a flavorless, white powder, is used in beverages, candies, confectionaries and supplements.

Researchers have wasted no time in finding health benefits associated with L-theanine, which has a relaxing effect attributed to its impact on various amines and neurotransmitters. Among the most recent results, Suntheanine has been shown the potential to protect against chemotherapy side effects,⁴⁰ prevent nerve cell degeneration⁴¹ and curb eating more than other tea phytochemicals.⁴²

Taiyo also supplies the high polyphenolic Sunphenon® line, featuring ingredients that contain varying amounts of catechins, including EGC. Research specific to Sunphenon’s concentrated polyphenols can inhibit cancer development,⁴³ reduce and delay muscle wasting in muscular dystrophy⁴⁴ and limit dental caries.⁴⁵ Scott Smith, vice president of Taiyo, reported current functional use trends for Sunphenon include weightloss/ thermogenic products, as well as antioxidant-rich formulas.

It remains to be seen how much functional tea the American market will accept; but if the recent flurry of tea-based research and product introductions is any indication, the market is expected to expand considerably. Kashi features green tea extract in its Heart-to-Heart™ cereal, Imagine Foods and other manufactures make tea flavored desserts (including ice cream), and Clif Bar uses green tea leaves and extract and in its functional Luna™ nutritional bar line. These are all popular and successful functional products. To American consumers, there is always a limit to how far trendy ingredients and flavors can go; but with no end in sight for scientific and governmental support of the health benefits of tea, the tea trade will continue its historical exploration to new territories.