October 2004

Vol. 3    No. 10

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Tea is the most popular beverage in many parts of the world and levels of consumption are increasing.  Historical records show that the enjoyment of tea goes as far back as 5000 years ago in China.  This stimulating beverage remained an important part of the cultures of China and Japan for thousands of years, and was finally imported to Europe in the 1500s.  Not until the early 1600s, however, did tea drinking become popular in England and America. 

There are four common categories of tea made from the same tea plant species (Camellia sinensis).  The difference in the varieties is the result of the methods of processing.  White tea is simply steamed leaves.  Oolong tea is partially fermented and green tea is steamed to stop the oxidation. Black tea undergoes several hours of oxidation during preparation (accelerated by heat and humidity).  The degree of processing after harvest changes the relative amounts and kinds of chemicals found in the final beverage

White Tea = boiled and dried.

Green Tea = withered by exposure to the air, steamed, rolled, and dried.

Oolong Tea = withered, shaken, fermented briefly, and dried.

Black Tea = withered, rolled, fully fermented, and dried.

Tea May Help You Lose Excess Weight

In experimental animal studies, tea results in a significant reduction of “high-fat diet-induced” body weight gain, and reduces the accumulation of fat in the  abdomen and liver, and prevents the development of hyperinsulinemia (elevated insulin levels associated with weight gain).¹  Research published in the American Journal of Clinical Nutrition suggests that an extract from green tea may help with weight loss by speeding up fat oxidation.²  Relative to a placebo, treatment with the green tea extract resulted in a significant increase in 24-hour energy expenditure. Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on energy expenditure.  Thus, tea may have specific benefits for losing excess body fat -- and should be an easy addition to the daily routine for anyone interested in becoming trimmer.

Oolong Tea Helps Diabetics

In a recent study published in the journal Diabetes Care, oolong tea was found to be very effective at lowering the blood sugar of diabetics on medications.  Compared to water, this variety of tea decreased blood sugars from an average of 229 mg/dl to 162.2 mg/dl.  This decrease was not due to any weight loss by the diabetics, but rather was a direct effect of the tea.  The mechanism by which tea lowers blood sugars is not known but it may be due to the insulin-like activity of compounds (polyphenols) found in teas, and the delay of glucose absorption through the intestine.

Synergetic Actions of Teas Prevent, and Maybe Treat, Cancers

Non-toxic approaches for the prevention and treatment of cancers are very important because of the relative ineffectiveness of drug therapy – little benefit has been realized for the patient’s survival of most cancers.  Anticancer drugs are also very toxic and costly.  Therefore, the likely possibility that green tea could improve the quality of your life is valuable information.

Heavy consumption of tea, especially green teas in Japan, has been associated with a decreased risk of cancer and artery disease (atherosclerosis).  In particular, people who drink green tea have been reported to have lower incidences of cancer of the esophagus and breast.  Most promising are the consistent findings in animal models that tea will reduce the development of skin, lung, colon, liver and pancreatic cancer.³ 

Even small concentrations of tea’s active ingredient (epigallocatechin-3-gallate) in the blood can stop the progression of growth of cancer cells by any or all of the above mechanisms.  Effective levels can be reached with as little as 2 to 4 cups a day.⁴  There may even be a benefit for people after they have developed cancer.  Green tea consumption of three or more cups daily has been found to delay the recurrence of breast cancer by about one-third.⁵

Protection from High Blood Pressure and Heart Disease

Tea may raise blood pressure right after drinking, but the long-term effects in daily users may actually be a lower blood pressure and tea may offer protection against the development of  hypertension.^6,7  In addition, other studies have shown tea to have anti-inflammatory, antithrombotic, and cholesterol-lowering effects – all important in preventing the atherosclerosis that leads to heart attacks and strokes.  Tea may further prevent artery disease by inhibiting the oxidation of cholesterol into a more artery-toxic, “oxidized,” form.^8,9

Other Health Benefits

Tea may protect against brain degeneration disorders, such as Parkinson's and Alzheimer's diseases.¹⁰  Green tea seems to be kind to the stomach – as opposed to coffee and “decaf”, which cause stomach inflammation – and tea prevents chronic gastritis.¹¹  Tea has also been shown to have antiviral and antibacterial properties.

Tea has a pleasant taste, which people quickly learn to enjoy.  One of the attractive qualities of tea, even green tea, is that it contains a desirable stimulant, caffeine, which relieves sleepiness and fatigue in most people. 

Overall, research has found that tea drinkers live longer and healthier.¹²   Add this battle tactic of daily tea drinking to the well-established benefits of an abundance of natural plant chemicals found in a healthy, low-fat, plant-food based diet, and you will have the best defense now known to science to keep disease away from your body.

References:

1)  Murase T, Nagasawa A, Suzuki J, Hase T, Tokimitsu I.  Beneficial effects of tea catechins on diet-induced obesity: stimulation of lipid catabolism in the liver.  Int J Obes Relat Metab Disord. 2002 Nov;26(11):1459-64.

2)  Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J.  Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.
Am J Clin Nutr. 1999 Dec;70(6):1040-5.

3)  Frei B, Higdon JV.  Antioxidant activity of tea polyphenols in vivo: evidence from animal studies.  J Nutr. 2003 Oct;133(10):3275S-84S.

4)  Lee YK, Bone ND, Strege AK, Shanafelt TD, Jelinek DF, Kay NE.  VEGF receptor phosphorylation status and apoptosis is modulated by a green tea component, epigallocatechin-3-gallate (EGCG), in B-cell chronic lymphocytic leukemia.
Blood. 2004 Aug 1;104(3):788-94.

5)  Inoue M, Tajima K, Mizutani M, Iwata H, Iwase T, Miura S, Hirose K, Hamajima N, Tominaga S.  Regular consumption of green tea and the risk of breast cancer recurrence: follow-up study from the Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC), Japan.  Cancer Lett. 2001 Jun 26;167(2):175-82.

6)  Yang YC, Lu FH, Wu JS, Wu CH, Chang CJ. The protective effect of habitual tea consumption on hypertension.  Arch Intern Med. 2004 Jul 26;164(14):1534-40.

7)  Hodgson JM, Puddey IB. Acute effects of tea on fasting and post meal blood pressure.  Asia Pac J Clin Nutr. 2004;13(Suppl):S71.

8)  Osada K, Takahashi M, Hoshina S, Nakamura M, Nakamura S, Sugano M.  Tea catechins inhibit cholesterol oxidation accompanying oxidation of low density lipoprotein in vitro.  Comp Biochem Physiol C Toxicol Pharmacol. 2001 Feb;128(2):153-64.

9)  Kurihara H, Fukami H, Toyoda Y, Kageyama N, Tsuruoka N, Shibata H, Kiso Y, Tanaka T.  Inhibitory effect of oolong tea on the oxidative state of low density lipoprotein (LDL).  Biol Pharm Bull. 2003 May;26(5):739-42.

10)  Weinreb O, Mandel S, Amit T, Youdim MB.  Neurological mechanisms of green tea polyphenols in Alzheimer's and Parkinson's diseases.  J Nutr Biochem. 2004 Sep;15(9):506-16.

11)  Shibata K, Moriyama M, Fukushima T, Kaetsu A, Miyazaki M, Une H.  Green tea consumption and chronic atrophic gastritis: a cross-sectional study in a green tea production village.  J Epidemiol. 2000 Sep;10(5):310-6.

12)  Nakachi K, Eguchi H, Imai K. Can teatime increase one's lifetime?  Ageing Res Rev. 2003 Jan;2(1):1-10.
 

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