(הכל אודות) תה סיני ירוק

המאמר התפרסם במקור במגזין האנגלי: The Journal of Chinese Medicine

ותורגם על ידי לעברית.

 

 

ישנם סוגי תה רבים, אך מקור כולם בצמח אחד. צמח זה נקרא: קמליה סינית. קמליה סינית הינה קרובת משפחה של הקמליה הפרחונית המוכרת היטב לגננים.

העלים הבודדים שנובטים בקצהו העליון  של הצמח, ובצמח זה בלבד, הם אלה שמהם מופקים כל סוגי התה: שחור, ירוק ואו-לונג. העלים מכילים קפאין, כמו גם כל סוגי התה המופקים מהם, אך במינון משתנה מסוג לסוג.

קמליה סינית הינו צמח ירוק-עד. בטבע הצמח גדל עד לגובה של 18 מטר ויותר. כאשר מגדלים את הצמח לתה, מקצצים את גובהו באופן קבוע לגובה של פחות ממטר אחד. עלים המיועדים לתה ירוק נתלשים באותו אופן כמו אלה המיועדים להכנת תה שחור. לאחר מכן הם עוברים הכנה בשלושה שלובים במשך יום אחד. אידוי – זהו שלב המתבצע מייד לאחר התלישה. העלים מונחים על מגש מתכת מעל להבה חמה כדי להפוך אותם לרכים וגמישים. החשיפה הפתאומית לחום הורסת את האנזימים המצויים בהם, אשר ללא כן היו גורמים לעלים לתסוס.

השלב הבא הינו גלגול העלים על מגשים מחוממים בכדי להפחית את תכולת הלחות הנמצאת בהם. התהליך מתבצע באופן ידני בעזרת האצבעות וכפות הידיים. לעתים אפילו בעזרת כל האמה.

השלב האחרון הוא שלב הייבוש בעזרת מייבשים מכניים גדולים. תה ירוק המיובש באופן כזה מכיל רק שני אחוזים מהלחות הבסיסית שהיתה בו מלכתחילה.

סוגי תה ירוק המיועדים ליצוא מגולגלים ומיובשים אפילו מספר פעמים. פעולה זו מאריכה אמנם את חיי המדף של המוצר, אך פוגמת בטעמו ובאיכותו.

 

אודות תה ירוק, שחור ואו-לונג

קיימים שלושה סוגי תה: ירוק, שחור ואו-לונג.

·       הירוק אינו מותסס כלל (Fermented)

·       התה השחור לעומתו, מותסס ב: 100%. תהליך ההתססה כולל השטחה של העלים המגולגלים על משטחי בטון או מרצפות, בחדר קריר ולח למשך מספר שעות. ההתססה משנה את הרכבו הכימי של עלה התה, ומאפשרת לאיכויות טעם מיוחדות לפרוץ.

·       תה או-לונג הינו מותסס באופן חלקי בדרגות משתנות.

 

 

ציטטות מהכתבים העתיקים אודות תה...

"שתיה קבועה של תה יכולה להרגיע את הנפש ולחזק את האנרגיה... להרבות את המרץ ולמנוע הזדקנות"

(Shen nong Ben cao Jing c. 200 A.D)

 

"משקה התה נמשל לטל המתוק היורד מהשמיים..."

(The classic of tea. 8th century, by Lu Yu)

 

"אנרגיית התה קרה, והוא מתאים ביותר לשתיה. כאשר אדם צמא, או סובל מכאב ראש, עיניו עייפות או ידיו ורגליו כבדות – מספר לגימות תה יחזירו אותו למוטב..."

 (The classic of tea. 8th century, by Lu Yu)

 

”שתית תה מרוה צמאון, מרחיקה מחלות, מקצרת את זמן השינה, מקלה על הפרעות במתן שתן, מחזקת את הראיה וכושר החשיבה. לא כדאי להפסיק לשתות תה אפילו ליום אחד..."

(A treatise on tea. Zhang Qiande)

 

..."ספל התה הראשון מלחלח את שפתי וגרוני,

הספל השני מוציאני מבדידותי...

הספל השלישי נובר בקרבי השומם, ולו אך למצוא חמשת-אלפי אותיות חסרות-פשר.

הרביעי מעלה דוק של זיעה ומפריש מנקבוביות עורי את הבלי החיים,

בספל החמישי אני מטוהר,

והששי מביאני אל סף האלמוות...

הספל השביעי – אה, איני יכול יותר לשתות!

אני אך מרגיש נשמת הרוח הקרירה נושבת בשרוולי גלימתי.

היכן הוא הוראי-סאן?

הניחני וארכב על משבי הרוח המתוקה ואדאה שמה..."

(The Book of Tea. Kakuzo Okakura)

 

מקורות מיתולוגיים, וההיסטוריה של התה

סיפור התה התחיל בסין העתיקה כבר לפני כ- 5000 שנה. על פי האגדה, הקיסר שן-נונג היה ממציאה של רפואת צמחי-המרפא. שן-נונג היה קיסר מחונן, מדען בעל שיעור קומה ופטרון האומנויות.

בזמנו הוא הוציא צו מלכותי (בהחלט מרחיק-ראות בהתייחס לתקופה העתיקה בה מדובר), כי אל לנתיניו לשתות מים אשר לא עברו הרתחה.

יום קיץ אחד, כאשר היה במסע ביקורים ברחבי ממלכתו, עצרו הוא ואנשי חצרו למנוחה בדרך. בהתאם להוראותיו המלכותיות החלו אנשי חצרו להרתיח מים כדי להרוות את צמאונם. מספר עלים יבשים משיח סמוך נפלו למים המבעבעים, אשר צבעם השתנה מיד לחום ירקרק. כמדען אשר סקרנותו אינה יודעת גבולות, החליט הקיסר לטעום מהמשקה בעל הניחוח שנוצר באקראי, והתפעל מטעמו הערב והמרענן.

וכך, בהתאם לאגדה, נוצר התה.

היסטוריונים רבים מוצאים בסיפור מעשה זה קרבה רבה לעובדות מאד מעשיות, ואינם מוציאים מכלל אפשרות שאינו רחוק כל כך מאמת היסטורית כלשהי הגלומה בעבר הרחוק.

צריכת התה חדרה לכל רבדי החברה הסינית, ולא פחות מכך לכל היבט בתרבות הסינית. בשנת 800 אחה"ס כתב המשורר לו-יו את הספר המוחלט אודות תה:  Ch'a Ching.   הוא קטלג את הטכניקות השונות שהיו קיימות לגידול והכנת התה בסין הקדומה.  היקפו העצום והסמכותי של הספר היקנו למחברו מעמד כמעט של קדוש עוד בימי חייו, ואפילו הקיסר העניק לו את חסותו. את הספר מאפיינים בבירור קוים של זן-בודהיזם, פילוסופיה אשר לו-יו גדל לאורה כבר משחר ילדותו. על פי מאפיינים אלה "יובאו" עקרונות טקס התה המפורסם (צ'ה נו יו) ליפן הקיסרית, על ידי מסיונרים זן בודהיסטיים בתקופה מאוחרת יותר.

זרעי צמח התה הראשונים יובאו ליפן ע"י הנזיר הבודהיסטי החוזר ייסי. נזיר זה נחשף לערכו הרב של התה כעזר מדיטטיבי – דתי. לפיכך הוכר ייסי כ"אבי טכס התה" ביפן. תואר כלל לא מבוטל לכל מי שמכיר את תרבות יפן. כתוצאה מהקשר זה נוצר החיבור הידוע ביפן שבין טכס התה לבין הזן-בודהיזם. התה קיבל כמעט מיד עם הגיעו ליפן הכרה ומימון קיסרי, והתפשט במהירות מחצר הקיסר והמנזרים לכל רבדי החברה ביפן העתיקה.

תוך זמן קצר הגיע התה למעמד של אמנות, תוך כדי היווצרות טכס התה המפורסם: הצ'ה – נו – יו (מים רותחים לתה). התאור המעודכן ביותר לצורת אמנות מורכבת זו נכתב כנראה ע"י ההיסטוריון האירי-יווני לפקדיו הראן. הוא היה אחד מהזרים הבודדים שהוענקה לו תעודת אזרח יפנית בתקופה עתיקה זו. הוא כתב מהתבוננות אישית:

..." טכס התה מצריך שנים של אימון והכנה כדי לקבל הסמכה... אולם, כל כולה של אמנות זו לפרטיה, מסמלת לא יותר מאשר הכנה והגשה של ספל תה... הנושא החשוב ביותר כאן הוא בכך כי הפעולה תתבצע בצורה המושלמת ביותר, המנומסת והחיננית ביותר וללא שום דופי אסטטי...".

שאיפה זו לשלמות של תוכן וצורה הביאה בעקבותיה ליצירת אמנויות ושרותים נלוים. שיטה מיוחדת של ארכיטקטורה התפתחה כדי ליצור את בתי-התה (צ'אסקי). על פי גישה זו עוצבו בתי-התה בפשטות האפיינית לבתי –יער.

המארחות היפניות המפורסמות, הגיישות, החלו גם הן להתמחות בהכנת טכס התה. ככל שיותר ויותר אנשים החלו להיות מעורבים בהתרגשות סביב עניין התה, כך הלכו ונעלמו הטוהר והפשטות הייחודיים לעקרונות הזן-בודהיזם. טכס התה הושחת והפך לקולני והמוני. "תחרויות תה" הפכו לארועים נוצצים בקרב החברה הגבוהה, בהם התחרו אצילי יפן תמורת פרסים כספיים מי יתן שם מקורי יותר לתערובות תה חדשות...

הענקת פרסי כסף, משי, שריוני קרב ותכשיטים יקרים, היתה מנוגדת בתכלית לאופי הצנוע והמקורי של טכס התה.

בעוד שהתה הגיע לרמת התפתחות גבוהה ביותר בסין וביפן, התחילו להסתנן למערב שמועות אודות משקה מיוחד זה מהמזרח הרחוק. כבר בעבר הרחוק החלו מובילי שיירות מסחר להזכיר במערב את שמעו, אך המידע היה מקוטע ובלתי ברור באשר לדרך הכנתו או צורתו. במקרה אחד אפילו נכתב כי עלי התה הורתחו, הומלחו, נטבלו בחמאה... ונאכלו!

האירופאי הראשון אשר נחשף באופן אישי לתה וכתב אודותיו, היה הנזיר הישועי הפורטוגזי, האב ג'ספר דה קרוז בשנת 1560. פורטוגל, בעלת הטכנולוגיה הימית המתקדמת ביותר אותם ימים, הצליחה להשיג את הסכם הסחר הראשון עם סין. במסגרת שליחות מסיונרית באותה משלחת-סחר ראשונה, טעם האב ג'ספר דה קרוז את טעם התה לראשונה.

הפורטוגזים פיתחו נתיב סחר דרכו הובילו תה לליסבון, בירתם. משם הובילו את התה אוניות סוחר הולנדיות לצרפת, הולנד וארצות הבלקן. באותה תקופה היתה הולנד בת-ברית פוליטית של פורטוגל. כאשר בשנת 1602 הופרה ברית זו, נכנסה הולנד עם ציה הימי המפואר לנתיב סחר עצמאי משלה עם המזרח הרחוק.

כאשר הגיע התה סוף סוף לאירופה, אליזבת הראשונה היתה בראשית שלטונה, ורמברנדט היה בן שש שנים בלבד. בעקבות הצלחת הצי ההולנדי בארצות האוקינוס השקט, הפך התה לאופנתי מאד בבבירת הולנד, דן האאג. בעיקרו של דבר היה זה עקב מחירו הגבוה יחסית (מעל מאה דולר לחצי ק"ג). במחיר כזה יכלו לקנותו רק העשירים. אט אט ככל שכמויות התה המיובא גדלו, ירד מחירו לצרכן. למרות שבתחילה ניתן היה לקנות את התה רק בבתי מרקחת יחד עם תבלינים חדשים כזנגוויל וסוכר, ניתן היה כבר בשנת 1675 לקנותו גם בחנויות מזון רגילות ברחבי הולנד.

 ככל שצריכת התה גברה באופן ניכר בשכבות החברה ההולנדית, רופאים ואנשי אקדמיה התווכחו באשר לערכו, או חוסר ערכו הבריאותי. ידועים בשם: "כופרי התה", הציבור הרחב התעלם מהם לחלוטין, והמשיך להנות ממנעמי התה. ויכוחים "מדעיים" אלה נמשכו בין השנים: 1635 – 1657. במהלך שנים אלה צרפת והולנד הובילו בצריכת התה המיובא את כל מדינות אירופה.

ככל שהנהיה אחר מוצרים אוריינטליים סחפה את אירופה, תה הפך להיות "דרך חיים". המבקר החברתי הנודע: המרקיז מארי דה רובין-שנטל, הזכיר לראשונה הוספה של חלב לתה. במהלך אותה תקופה, החלו פונדקים הולנדים להגיש תה כתוספת לסעודה. בעלי מסבאות סיפקו לאורחיהם מערכת תה נישאת, הכוללת יחידת חימום. כך יכול היה ההולנדי העצמאי להכין לבדו תה לעצמו ולחבריו בגן המסבאה, בחצר.

תה נשאר פופולרי בצרפת עוד למשך כ- 50 שנה. אח"כ התחלפה העדפת הצרפתים ביין, שוקולד וסוגי קפה אקזוטיים.

בשנת 1650 היו ההולנדים מעורבים באופן פעיל במסחר בכל רחבי העולם המערבי. פיטר סטויווסנט ייבא את התה הראשון לאמריקה, למתיישבים ההולנדים בניו אמסטרדם. מאוחר יותר שונה שמה לניו יורק ע"י האנגלים.  המתיישבים בקולוניות אלה היו שתייני תה מושבעים.

אכן, כאשר נרכשה ניו יורק האנגלים מצאו שישוב קטן זה צרך יותר תה באותה התקופה מאשר כל תושבי אנגליה גם יחד...

בריטניה הגדולה היתה האחרונה מתוך שלושת המעצמות הימיות להכנס לנתיבי הסחר עם סין ומזרח הודו. הסיבה לכך היתה בעיקר קשורה לעלייתו הפרובלמטית של בית סטיוארט למלוכה, וכן מלחמת האזרחים של קרומוול. דוגמאות התה הראשונות הגיעו איפה לאנגליה בין השנים 1652 – 1654. במהרה הפך התה באנגליה כה פופולרי עד שהחליף את השיכר בתור המשקה הלאומי הבריטי.

כמו בהולנד כך באנגליה, היתה זו האצולה שסיפקה את האישור החברתי לקבלת התה. המלך צ'רלס השני נשא לאשה בהיותו בגלות, את קטרינה דה ברגנצה הפורטוגזית (1662). צ'רלס עצמו גדל בבירה ההולנדית. כתוצאה מכך, גם הוא גם מלכתו היו שתייני תה מושבעים. כאשר מוסדה שוב המלוכה באנגליה, הביא הזוג המלכותי את מסורת שתיית התה המזרחית לבירתם.

שגעון התה סחף את אנגליה באותו אופן שסחף בזמנו את תושבי צרפת והולנד. יבוא התה זינק מ: 18,000 ק"ג בשנת 1699, לממוצע שנתי של 109,000 ק"ג בשנת 1708...

התה הפך במהרה למשקה המועדף על כל שכבות האוכלוסייה.

 

  חזרה לראש העמוד

מחקרים רפואיים על תה, בני זמננו.

הקטעים הבאים, המובאים בשפת המקור באנגלית, הינם אוסף של קטעי ידיעות רפואיות בנושא ערכו הבריאותי של התה. הקטעים לוקט ממקורות שונים, ונאספו ע"י עורכי המגזין: The Journal of Chinese Medicine באנגליה.

 

Green Tea and Rheumatoid Arthritis

Studies in mice suggest that green tea antioxidants may have a powerful effect in reducing the incidence and severity of rheumatoid arthritis. Polyphenols (antioxidants found in green tea) possess much more potent antioxidant activity than well-known antioxidants such as vitamin C and vitamin E. A research team from Western Reserve University, Cleveland, Ohio has now focused on the effect of these polyphenols in rheumatoid arthritis. Mice used in the Cleveland study were fed either plain water or water enriched with green tea polyphenols, with dosages roughly equivalent to a human drinking four cups of green tea per day. Each of the mice were then injected with collagen, rendering them vulnerable to collagen-induced arthritis - a condition very similar to human rheumatoid arthritis. The study showed that mice fed green tea polyphenols "were significantly less susceptible to the development of collagen-induced arthritis, and if they developed arthritis, the disease was late in onset and mild in comparison to mice not given green tea polyphenols". (Proceedings of the National Academy of Sciences 1999;96:4524-4529). Meanwhile a US study has shown that drinking at least one cup of tea a day can reduce the risk of heart attack by 44%. The health benefits are thought to be derived from ingredients known as flavanoids, a type of antioxidant found in all types of tea. Flavanoids are thought to neutralise the effect of free radicals, a highly reactive molecule which travels around the body causing chemical reactions which can damage cells, including those in the heart tissues. A previous Dutch investigation of more than 800 men between 65 and 84 showed that drinking even more tea - between three and four cups a day - decreased risk of death from coronary heart disease by 58%. In 1991 there were just 153 studies on tea, while in 1998 there were 625 published papers. In a further Japanese study, tea without sugar has been found to be good for teeth and gums. Tea contains tannin fluoride which appears to help prevent plaque. "An increase of just one cup a day could prove invaluable in the fight against gum disease," said the British Dental Health Foundation.

 

TEA
A Chinese study has shown that men who drink at least 1 cup of green tea per week for 6 months have a reduced risk of cancer of the colon, rectum or pancreas (Int. J. Cancer 1997, 70, 255-258). Research at the Karolinska Institute in Stockholm, Sweden has shown that a compound found in green tea can inhibit angiogenesis in mice, the process in which blood vessel growth is stimulated. The finding suggests that the compound may be useful in fighting malignant tumors, which must form new blood vessels in order to grow. Drs. Yihai Cao and Renhai Cao report that green tea, and one of its components, epigallocatechin-3-gallate (EGCG), significantly prevents the growth of new blood vessels in animals. The researchers conclude that long-term consumption of 2 to 3 cups of green tea might inhibit angiogenesis, an effect that may be beneficial in the prevention of cancers as well as other angiogenesis-dependent diseases, such as diabetic retinopathy - an eye disease that is a common cause of blindness. The researchers warn that where angiogenesis is important, as in pregnancy or in patients with healing wounds, people should not drink large amounts of tea. (Nature 1999;398:381-382). Another study has shown that drinkers of one or more cups of black tea a day are 40% less likely to suffer a heart attack than non-drinkers, whilst coffee seems to have no significant effect on heart attack risk (American Journal of Epidemiology 1999;149:162-167). A case-control study of more than 1,200 Canadian men led by researchers at the University of Toronto and recently published in the International Journal of Cancer, investigated the association of prostate cancer with consumption of alcoholic and other beverages, including tea, coffee and cola. Of the beverages studied, only tea consumption (of more than two cups per day) was associated with a decrease in risk of prostate cancer.

 

TEA

More exciting tea studies continue to pour in. In recent months, the following discoveries have been reported:

·        Epigallocatechin gallate, or EGCG, an antioxidant found in green tea is at least 100 times more effective than vitamin C and 25 times better than vitamin E at protecting cells and their genetic material, DNA, from damage believed to be linked to cancer, heart disease and other potentially life-threatening illnesses, according to research carried out at the University of Kansas Lawrence. The antioxidant has twice the antioxidant benefit of resveratrol, found in red wine. Green tea has another advantage over vitamin E in that excessive amounts of antioxidants found in water soluble green tea are excreted by the body, whilst the body absorbs and retains fat-based vitamins such as vitamin E, even at potentially harmful levels.

·        The above research indicated that while EGCG is also present in black and oolong tea, there is less than half as much because green tea is steamed immediately after it is picked, which prevents the leaves from oxidizing, thus preserving the EGCG. By contrast, according to papers presented at the Second International Scientific Symposium on Tea and Human Health in Washington DC, black tea as high in antioxidants as green tea. Taking milk in tea does not dilute the medical power of the antioxidants, which are released from the tea leaves within five minutes of brewing. To gain maximum benefit from black tea, therefore, it needs to be brewed traditionally in a pot and left for five minutes before pouring. Black tea is made by exposing the leaves to air, which turns them reddish brown and gives black tea its flavor. Green tea involves the least processing. Oolong tea is halfway between green and black in terms of processing

·        Dr Yoshimasa Yamamoto, of Showa University in Japan, says green tea contains chemicals called catechins that "show strong antibacterial activity" against helicobacter, a bacterium which earlier this decade was discovered to be the cause of the majority of stomach ulcers. "The level required for such activity... is easily reached in the stomach after drinking a cup of green tea," he told the American Society of Microbiology's annual conference. And a Dutch team has found that garlic, even in low concentrations, especially when taken in conjunction with chemicals that reduce stomach acidity, also inhibits the growth of Helicobacter.

·        The Tea Council of the USA has developed a glossary to explain terms related to substances found in tea: Phytochemicals: naturally occurring plant compounds, many of which are thought to play a role in decreasing the risk of cancer and heart disease and of boosting the immune system. Polyphenols: a broad class of antioxidant phytochemicals found throughout the plant kingdom. Flavonoids: a class of polyphenolic phytochemicals that are antioxidants. Flavonols: a group of flavonoids found in tea and many fruits and vegetables that are antioxidants. Cathechins: a group of antioxidant flavonoids also found in tea and some fruits. Examples include epicatechin and epigallocatechin gallate. Epigallocatechin gallate: the principal cathechin in green and black teas, and a strong antioxidant. It has been shown to reduce formation of lung, oesophageal and skin tumours in research. Theaflavins: black tea flavonoids produced from cathechins during tea manufacturing, and colored reddish orange. They are strong antioxidants and have proved in research to reduce oesophageal tumours and oxidative damage to lung tissue.

·        Thearubigins: black tea flavonoids, which are brown and astringent, produced from cathechins during tea manufacturing. Gallic acid: a polyphenol in black and green tea with established antioxidant activity.

·        Dr. Junshi Chen of the Chinese Academy of Preventive Medicine in Beijing studied patients who had been diagnosed with precancerous oral lesions. Chen had one group of patients rinse their mouths with the components found in green and black tea. He also painted a mixture of tea and glycerin on the patients' lesions. After six months, the size of the lesions had declined in 38% of the treated group and increased in 3%; while the lesions decreased for 10% of the untreated patients and grew in 6%. There also were significant differences in the extent of DNA damage in the treated group and about a third less proliferation of pre-cancerous cells. The results suggest that other epithelial cancers might be similarly affected by treatment with tea.

·        Tea might also play a role in retarding the development of lung cancer, according to studies by a researcher from the American Health Foundation of Valhalla, N.Y. The researcher, Fung-Lung Chung, found that consuming either black or green tea retarded the development of lung tumours in mice and rats.

·        Another study, conducted on humans by J.E. Klaunig of the Indiana University School of Medicine, found that black and green tea reduced the level of oxidative stress, particularly in smokers. Oxidative stress is cell damage associated with environmental factors, such as chemicals, heavy metals and ultraviolet light.

·        Apparently decaffeinated tea has most, if not all, of the active chemical components that appear to be acting as antioxidants in tea.

·        When EGCG from green tea is added to sulindac, the mixture was found to be two to eight times more effective in killing lung cancer cells than sulindac alone, according to Japanese Cancer Association. EGCG was also tested on tamoxifen, a drug used to treat breast cancer, and the compound was found to be twice as effective in killing the cells than the drug alone. In both cases the combined medication also reduced the risk of side effects.

·        Research at Oregon State University, showed that drinking green and black tea inhibited the development of pre-cancerous lesions in the colons of rats. Other studies suggest similar effects in oesophageal and stomach cancer.

·        A nutritional breakdown by experts at Britain's Tea Council suggests tea is a major source of the trace mineral manganese (needed for thyroid and sex hormone production as well as healthy bones) and a provider of potassium, vital for maintaining a normal heartbeat. Three or four cups per day, with milk, provides 16 per cent of the UK recommended intake of calcium, a tenth of our folic acid needs and a quarter of the vitamin B2 requirement. Tea is also one of the few natural dietary sources of fluoride which strengthens teeth. Research at Newcastle University suggested three cups a day can help prevent tooth decay in children.

·        In 1993, a Lancet report showed people with the highest intake of the anti- oxidant flavonoid had less than half the risk of dying of coronary heart disease than people with the lowest consumption. And a Dutch study suggested drinking five cups a day could cut the risk of suffering a stroke by up to 70 per cent.

·        The results of a recent Australian Government research project indicated
that mice drinking green tea experienced an average reduction of 18 per cent in skin cancer, while those drinking black tea showed a reduction of 54 per cent.

·        Tea drinking increases concentration and the ability to learn, according to research by Kimron Shapiro, a professor of psychology at the University of Wales. It is especially beneficial to people when they are doing two things at once and also helps them concentrate when they are performing one task after another. The research demonstrated that caffeine was not responsible because those drinking tea out-performed those given a caffeine-only drink.

·        Britons drink 185 million cups of tea a day.

·        Powdered and instant tea contains only small percentages of antioxidants compared with freshly brewed tea.

 

More about green tea

Now we can not only drink green tea but cover ourselves with it. Excited by the proven antioxidant properties of green tea when applied to the skin, cosmetic companies are increasingly using it in their skin products. The Estee Lauder company, for example, currently has nine products that include tea. Japanese research has indicated a correlation between green tea and a reduction in the incidence of skin cancer. Topical application of green tea has been shown to reduce skin damage caused by free radicals such as sun and pollution.

It’s tea time again

Yet more information flows in about the beneficial effects of tea. Scientists in Hunan Province, China have discovered that catechol, or catechin, in tea can lead to cancer cells "committing suicide". The most effective kind of tea is non-fermented green tea but half-fermented (oolong) and wholly-fermented black teas can also kill cancer cells. The effect of different teas has also been found to vary according to its type and growing area. In the USA, scientists from the Medical College of Ohio and the University of Toledo have also demonstrated the anti-cancer effect of epigallocathechin-3 gallate (EGCG), a natural component of green tea. Their studies, however, indicate that black tea does not have the same effect because EGCG is destroyed in its preparation.

GREEN TEA NEWS is happy to offer more research confirming the benefits of green tea, our favourite drink. A study on rats with carcinoma of the mammary gland showed that the group treated with green tea catechins had a significantly higher survival rate and the mammary tumours were palpably smaller than the control group (Cancer Lett 83:149-156; 1994). In China, a population-based, case-control study of oesophageal cancer in urban Shanghai suggested a protective effect of green tea consumption. These findings are consistent with studies in laboratory animals, indicating that green tea can inhibit oesophageal carcinogenesis (J Natl Cancer Inst 86:855-858; 1994). In Japan, a study of 1,306 males who received the retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and December 1988, showed serum total cholesterol levels were found to be inversely related to the consumption of green tea while no association was noted with serum triglycerides and high-density lipoprotein cholesterol. Adjusted mean concentrations of total cholesterol were 8 mg/dl lower in men drinking nine cups or more of green tea per day than in those consuming zero to two cups per day. (Prev Med 21:526-531; 1992). Another Japanese study found that "the main constituent of Japanese green tea, EGCG, is a practical cancer chemopreventive agent available in everyday life" (Prev Med 21:503-509; 1992). Further studies showed that i. "tea components possess antimutagenic and anticarcinogenic effects, and ... they ... protect humans against the risk of cancer by environmental agents" (Prev Med 21:351-360; 1992); ii. polyphenolic compounds from Japanese green tea have an anticaries effect (Caries Res 25:438-443; 1991); iii. EGC and EGCG isolated from green tea leaves, have been reported to prevent or diminish the occurrence of epileptic discharges induced by iron ions (Neurochem Res 17:585-590; 1992); iv. Long-term administration of EGCG extracted from green tea to mice prevented radiation-induced increase of lipid peroxides in the liver and significantly prolonged life span after lethal whole-body X-irradiation (Life Sci 50:147-152; 1992); v. extracts of Japanese green tea leaves inhibited the growth of various bacteria causing diarrhoeal diseases (Nippon Saikingaku Zasshi 44:669-672; 1989). Good news for drinkers of black tea though. Another study showed that black tea, green tea, decaffeinated black tea and decaffeinated green tea all had marked effects on inhibiting ultraviolet B light-induced skin carcinogenesis in mice. The effects of the green and black teas were comparable, with the decaffeinated versions slightly less effective (Cancer Res 54:3428-3435; 1994).

GREEN TEA

The British Medical Journal has published a Japanese study on the benefits of green tea consumption in preventing cardiovascular disease, liver disorders and possibly cancer. The study, begun in 1986, concerned 1371 men over the age of 40. Tea consumption was classified as less than 3 cups, between 4 and 9 cups, and over 10 cups per day. It was found that consumption of green tea was significantly associated with lower serum concentrations of lipids and lipoproteins. "An increase in consumption substantially decreased serum total cholesterol and triglyceride concentrations, and this strong association remained almost unaltered even after age, cigarette smoking, alcohol consumption and relative body weight were controlled for". Interestingly it was found that those who drank the most green tea (more than 10 cups) were also the heaviest smokers, but that whilst levels of lipid peroxides were generally higher among smokers than non-smokers, those smokers who drank more than 10 cups had lipid peroxide levels similar to non-smokers. The study also showed that consumption of green tea reduced liver cell damage and resulted in slightly lower (but not abnormal) haemoglobin concentration. The study also suggests that green tea has protective effects on the development of cancer.

TEA
According to Dutch research, drinking tea protects against the build-up of cholesterol in the arteries, especially in women. Results indicated that people who drank one to two cups of tea a day were 46% less likely to develop severe atherosclerosis, rising to 69% in those who drank four cups of tea a day. The protective benefit of tea was most pronounced among women. The authors acknowledge that at least in the West, people who drink tea generally have a healthier lifestyle and diet, which may account for the findings. In this study, for example, the researchers found that people who drank more tea tended to be lean, had a healthy diet, and smoked less. However the fairly high levels of antioxidant flavonoids in black tea are thought to protect against arterial plaques, the fatty deposits that clog arteries, by preventing fat from being deposited on artery walls (Archives of Internal Medicine 1999;159:2170-2174). Green tea appears to speed up calorie burning, including fat calorie burning, according to researchers from the University of Geneva in Switzerland. The study authors report that, compared with placebo, treatment with green tea was associated with a "significant increase" (+4%) in daily energy expenditure. They believe that the caffeine interacts with the flavonoids in tea to alter the body's use of norepinephrine, a chemical transmitter in the nervous system, and increase the rate of calorie burning (American Journal of Clinical Nutrition, November 1999). In Japan, The Saitama Cancer Research Institute has discovered that women with a history of breast cancer who drank 5 cups of tea daily were 50% less likely to have a recurrence than women who drink none or less than 5 daily cups. In a separate study, drinking strong tannin-rich tea has been shown to benefit genetic haemochromatosis, since tannates and other ligands inhibit the absorption of iron (BMJ no. 7168 (7th Nov '98).

Infertility and tea

A new study suggests that drinking at least a half cup of tea a day doubles a woman's chances of getting pregnant. The study, reported in the American Journal of Public Health, said that one explanation for this effect may be a chemical component in tea that affects DNA and the fluid that aids a woman's eggs in the fertilization process. No other caffeinated beverage, including coffee and Pepsi Cola, had any impact on the women. The study didn't determine whether green, black or herbal teas are most effective, nor did it separate out the effect of caffeinated and decaffeinated teas. It should be noted that previous studies have suggested that tea can cause miscarriage and more work needs to be done before the benefit is proven.


Carrots and tea

 Macular degeneration is the leading cause of blindness for the over-65's in the US. A large study by the Eye Disease Case-Control Study Group has found that a high intake of carotenoids (found most abundantly in yellow vegetables such as carrots and squash) lowers the risk of developing macular degeneration. In a separate study on 552 Dutch men, it has been found that the consumption of large quantities of black tea (more than 4.7 cups a day), and other foods containing flavonoids (fruit and vegetables), could help to reduce the risk of strokes. Previous studies have linked flavonoids to protection against heart attacks. Flavonoids are also found in red wine and green tea, both of which seem to offer protection against heart disease. Finally a new study suggests that a substance in watercress may lower the risk of lung cancer in smokers. The study - presented at a seminar held by the American Cancer Society - found evidence that the substance blocks a chemical pathway from tobacco smoke to lung cancer.

Other tea research

Inhibition of mammary gland carcinogenesis by green tea catechins and other naturally occurring antioxidants in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[alpha]anthracene.

Effects of the naturally occurring antioxidants on mammary gland carcinogenesis were examined in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[alpha]anthracene (DMBA). Groups of 15-16 7-week-old rats received a 50 mg/kg body weight intra-gastric dose of DMBA, and starting one week thereafter placed on diet containing 0.4% catechol, 1.0% gamma-oryzanol, 2.0% phytic acid, 1.0% green tea catechins (GTC), 1.0% tannic acid or basal diet alone for 35 weeks. Although the final incidences and multiplicities of mammary tumors were not significantly different between DMBA-treated groups, the numbers of survivors in the
antioxidant-treated groups at the end of the experiment at week 36 were significantly higher than in the basal diet group. In particular, the survival rate of the GTC group at 93.8% strongly contrasted with that of only 33.3% for rats on the basal diet. At the end of week 18, when all the animals were still alive, the average size of palpable mammary tumors was significantly smaller in the catechol, phytic acid and catechins groups. These results indicate that antioxidants, and GTC in particular, inhibit rat mammary gland carcinogenesis after DMBA initiation.Hirose M, Hoshiya T, Akagi K, et al. Inhibition of mammary gland carcinogenesis by green tea catechins and other naturally occurring antioxidants in female Sprague-Dawley rats pretreated with 7,12 dimethylbenz[alpha]anthracene. Cancer Lett 83:149-156; 1994.

Scavenging action of green tea extracts on singlet oxygen and preventive effect on lipid peroxidation Singlet oxygen (1O2) produced by illuminated photosensitizer Rose Bengal was detected by its bleaching effect on N,N-dimethylnitrosoaniline(DMNA). The 1O2 could be scavenged by green tea extracts (GTE), with the scavenging action being obvious at the early stage of photosensitized oxidation. The higher the concentration of GTE in the photooxidation reaction system, the stronger the 1O2 scavenging action. The scavenging effect of the fresh GTE solution on singlet oxygen was better than that of old solution. The preventive effects of GTE on lipid peroxidation induced by 1O2 in ghosts and microsomal membranes were also observed. Malondialdehyde (MDA) production was found to be completely inhibited by a high concentration of GTE in the reaction system.Wu Y. [Scavenging action of green tea extracts on singlet oxygen and preventive effect on lipid peroxidation] Chung Kuo I Hsueh Ko Hsueh Yuan Hsueh Pao 15:354-359; 1993.

Inhibitory effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on ultraviolet B light-induced skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated SKH-1 mice. In a previous study (Z. Y. Wang et al., Cancer Res., 52: 1162-1170, 1992), we found that administration of a water extract of green tea leaves as the sole source of drinking fluid inhibited ultraviolet B light (UVB)-induced carcinogenesis in SKH-1 mice previously initiated with 7,12-dimethylbenz[a]anthracene (DMBA). In the present study, we compared the effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice. A 1.25% water extract of each kind of tea leaf (1.25 g tea leaf/100 ml water) was prepared by passing 4 liters of hot water through 50 g of tea leaves in a Bunn tea brewing machine. The mean concentrations of solids in multiple samples of 1.25% black tea, green tea, decaffeinated black tea, and decaffeinated green tea analyzed during the course of this study were 4.23, 3.94, 3.66, and 3.53 mg/ml, respectively. These concentrations of tea solids are similar to those present in tea brews ingested by humans. Female SKH-1 mice were treated topically with 200 nmol of DMBA, followed 3 weeks later by irradiation with 30 mJ/cm2 of UVB twice weekly for 31 weeks. UVB-induced formation of skin tumors was markedly inhibited by oral administration of 0.63 or 1.25% black tea, green tea, decaffeinated black tea, or decaffeinated green tea as the sole source of drinking fluid 2 weeks prior to and during 31 weeks of UVB treatment. Administration of each of the eight tea preparations not only inhibited the number of tumors, but tumor size was also markedly decreased. Histopathological examination of each tumor showed that oral administration of the eight tea preparations had a marked inhibitory effect on the formation of UVB-induced keratoacanthomas and carcinomas. Administration of 1.25% black tea, green tea, decaffeinated black tea, or decaffeinated green tea inhibited the number of keratoacanthomas per mouse by 79, 78, 73, or 70%, respectively, and the number of carcinomas per mouse was inhibited by 93, 88, 77, or 72%, respectively. In summary, administration of black tea was comparable to green tea as an inhibitor of UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice. Oral administration of decaffeinated black tea or decaffeinated green tea also had a marked inhibitory effect on UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice, but these tea preparations were slightly less effective than the regular teas at the high dose level.Wang ZY, Huang MT, Lou YR, et al. Inhibitory effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on ultraviolet B light-induced skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated SKH-1 mice. Cancer Res 54:3428-3435; 1994.

A potent thromboxane formation inhibitor in green tea leaves.

A ninhydrin positive compound (L2) now identified as 2-amino-5-(N-ethylcarboxyamido)-pentanoic acid, from unprocessed tea leaves was a potent inhibitor of thrombin-stimulated thromboxane formation in rabbit whole blood (Ali and Afzal; Prostaglandins, Leukotrienes and Medicine, 27: 9, 1987). In the present study, processed and unprocessed tea leaf extracts were given to rats to consume for a period of eight weeks. Cholesterol and thromboxane levels were measured in the serum obtained from clotting the blood at 37 degrees C. A significant reduction in thromboxane levels was observed in rats taking unprocessed tea extract. This reduction was equally distributed in adult as well as in juvenile rats. However no appreciable changes in the levels of thromboxane were noticed in the serum of rats taking processed tea extracts. This might be due to the presence of a labile component which is destroyed during the processing of green tea leaves. A decreased level of cholesterol was observed in rats consuming unprocessed tea extract. This decrease could be linked to the decrease in thromboxane levels as observed. Processed tea refers to commercially available tea of different brands while unprocessed tea refers to dried green tea leaves. Ali M, Afzal M, Gubler CJ, Burka JF. A potent thromboxane formation inhibitor in green tea leaves.Prostaglandins Leukot Essent Fatty Acids 40:281-283; 1990.

Reduced risk of esophageal cancer associated with green tea consumption.

BACKGROUND: Studies in laboratory animals have suggested inhibitory effects of green tea on the induction of some cancers, notably, esophageal cancer. However, only a few epidemiologic studies have evaluated green tea as a potential inhibitor of human esophageal cancer. PURPOSE: Our purpose was to evaluate the relationship between green tea consumption and the risk of esophageal cancer. METHODS: This esophageal cancer study was part of a larger multicenter, case-control study that included three other gastrointestinal sites (pancreas, colon, and rectum). Medical records of patients aged 30-74 years old who were diagnosed with esophageal cancer from October 1, 1990, through January 31, 1993, were identified from the Shanghai Cancer Registry, which covers 6.8 million people in the urban area of Shanghai, People's Republic of China. During the ascertainment period, records of 1016 eligible cases of esophageal cancer were identified. Control subject records were selected by frequency matching in accordance with the age-sex distribution of the four gastrointestinal cancers ascertained by the cancer registry during 1986-1987. Patient interviews were then conducted using a structured, standardized questionnaire to obtain information on demographic characteristics, residential history, height and weight, diet, smoking, alcohol and tea drinking, medical history, family history of cancer, occupation, physical activity, and reproductive history. RESULTS: Of the 902 patients interviewed, 734 (81.4%) had their disease pathologically confirmed. There were 1552 control subjects interviewed, including 240 alternates. All analyses of tea effects were conducted separately among men and women and all were adjusted for age. After further adjustment for other known confounders, a protective effect of green tea drinking on esophageal cancer was observed among women (odds ratio [OR] = 0.50; 95% confidence interval [CI] = 0.30-0.83), and this risk decreased (P for trend < or = .01) as tea consumption increased. Among men, the ORs were also below 1.00, although not statistically significant. ORs for green tea intake were estimated among those persons who neither smoked nor drank alcohol. In this subset, statistically significant decreases in risk among tea drinkers were observed for both men (OR = 0.43; 95% CI = 0.22-0.86; P for trend = .05) and women (OR = 0.40; 95% CI = 0.20-0.77; P for trend < .001). CONCLUSIONS: This population-based, case-control study of esophageal cancer in urban Shanghai suggests a protective effect of green tea consumption. Although these findings are consistent with studies in laboratory animals, indicating that green tea can inhibit esophageal carcinogenesis, further investigations are definitely needed.Gao YT, McLaughlin JK, Blot WJ, et al. Reduced risk of esophageal cancer associated with green tea consumption. J Natl Cancer Inst 86:855-858; 1994.

Inhibitory effect of tea catechins on collagenase activity.

A major purpose of this study was to examine inhibitory effect of the catechin derivatives from Japanese green tea Camellia sinensis on collagenase activity. The crude tea catechins, which contain (+)-catechin (C), (-)-epicatechin (EC), (+)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg), were tested for their ability to inhibit the prokaryotic and eukaryotic cell derived collagenase activities. Among the tea catechins tested, ECg and EGCg showed the most potent inhibitory effect on collagenase activity when an optimal concentration of tea catechins (100 micrograms/ml) was added to reaction mixture containing collagenase and collagen. Preincubation of collagenase with tea catechins reduced the collagenase activity as well. In contrast to ECg and EGCg, the other four tea catechins (C, EC, EGC, and GC) did not show any collagenase inhibitory effect. Our results suggest that the steric structure of 3-galloyl radical is important for the inhibition of collagenase activity. The collagenase activity in the gingival crevicular fluid from highly progressive adult periodontitis was completely inhibited by the addition of tea catechins. These results demonstrated that tea catechins containing galloyl radical possess the ability to inhibit both eukaryotic and prokaryotic cell derived collagenase.Makimura M, Hirasawa M, Kobayashi K, et al. Inhibitory effect of tea catechins on collagenase activity. J Periodontol 64:630-636; 1993.

Green tea consumption and serum lipid profiles: a cross-sectional study in Northern Kyoto Japan
METHODS. The relation between green tea consumption and serum lipid concentrations was examined using cross-sectional data on 1,306 males who received the retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and December 1988. RESULTS. After adjustment for rank, smoking, alcohol use, physical activity, and body mass index, serum total cholesterol levels were found to be inversely related to the consumption of green tea while no association was noted with serum triglycerides and high-density lipoprotein cholesterol. Adjusted mean concentrations of total cholesterol were 8 mg/dl lower in men drinking nine cups or more per day than in those consuming zero to two cups per day. Serum cholesterol levels were inversely associated with traditional Japanese dietary habits (intake of rice and soy bean paste soup) and positively associated with Westernized habits. Additional adjustment for these dietary variables did not alter the inverse relation between green tea and total cholesterol.Kono S, Shinchi K, Ikeda N, et al. Green tea consumption and serum lipid profiles: a cross-sectional study in northern Kyushu, Japan.
Prev Med 21:526-531; 1992.

Anticarcinogenic effects of (-)-epigallocatechin gallate.

BACKGROUND. Our research objective is to develop nontoxic cancer chemopreventive agents and to apply these agents in treating humans. We are identifying agents that inhibit the process of tumor promotion in two-stage carcinogenesis experiments on mouse skin. METHODS. We review (a) the inhibitory effect of penta-O-galloyl-beta-D-glucose (5GG) on tumor promotion by teleocidin, one of the 12-O-tetradecanoylphorbol-13-acetate (TPA)-type tumor promoters (5GG is structurally similar to (-)-epigallocatechin gallate (EGCG) and is isolated from hydrolyzed tannic acid); (b) the inhibitory effects of EGCG, the main constituent of Japanese green tea, on tumor promotion with two tumor promoters, teleocidin and okadaic acid, a non-TPA-type tumor promoter; (c) the mechanisms of action of EGCG, a single application of which reduced the specific binding of [3H]TPA and [3H]okadaic acid to a particulate fraction of mouse skin; and (d) the anticarcinogenic effects of EGCG on duodenal carcinogenesis induced by N-ethyl-N'-nitro-N-nitrosoguanidine in male C57BL/6 mice. EGCG is a nontoxic compound. CONCLUSION. We believe that the main constituent of Japanese green tea, EGCG, is a practical cancer chemopreventive agent available in everyday life.Fujiki H, Yoshizawa S, Horiuchi T, et al. Anticarcinogenic effects of (-)-epigallocatechin gallate. Prev Med 21:503-509; 1992.

Protective activity of tea and catechins against Bordetella pertussis

We examined the bactericidal activity of tea and catechins against Bordetella pertussis. Green tea, black tea and coffee showed marked bactericidal activity at their concentrations in beverages, while pu-erh tea killed the bacteria in a moderate way. (-) Epigallocatechin gallate (EGCg) and theaflavin digallate (TF3) showed also marked bactericidal activity. Green tea and black tea also effectively blocked the adhesion of B. pertussis to HeLa and CHO cells, whereas ECGg and TF3 could not. EGCg and TF3 markedly inactivated leuco-lymphocytosis promoting activity of pertussis toxin. Black tea showed slight but significant inactivation of the activity, whereas green tea showed no inactivation. These results suggest that green tea, black tea, EGCg and TF3 might act as prophylactic agents against pertussis infection.Horiuchi Y, Toda M, Okubo S, et al. [Protective activity of tea and catechins against Bordetella pertussis]. Kansenshogaku Zasshi
66:599-605; 1992.

Tea components: antimutagenic and anticarcinogenic effects.

BACKGROUND. Tea from the Camellia sinensis species of the Theaceae family is one of the most ancient and, next to water, the most widely consumed beverage in the world. Since tea contains several polyphenols and since several other naturally occurring dietary polyphenols have shown antimutagenic effects in bacteria and anticarcinogenic effects in animal bioassay systems, we studied whether polyphenols extracted from Chinese green tea (GTP) also possess antimutagenic and anticarcinogenic effects. RESULTS. GTP and its constituent epicatechin derivatives were found to interact with hepatic cytochrome P450 (P450) and inhibited the P450-dependent mixed-function oxidase enzymes in skin and liver. GTP and its epicatechin derivatives exhibited antimutagenic effects in several test systems. GTP showed substantial anti-skin-tumor-initiating and anti-skin-tumor-promoting activities when assessed in murine skin tumorigenesis bioassay systems. In these model systems polyaromatic hydrocarbons, benzo[a]pyrene (BP), 3-methyl-cholanthrene, 7,12-dimethylbenz [a]anthracene, and (+)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (an ultimate carcinogenic metabolite of BP) were used as model skin carcinogens. The feeding of GTP in drinking water to SKH-1 hairless mice also afforded significant protection against ultraviolet-B-radiation-induced skin photocarcinogenesis .

CONCLUSIONS. These data suggest that tea components possess antimutagenic and anticarcinogenic effects, and that they could protect humans against the risk of cancer by environmental agents.Mukhtar H, Wang ZY, Katiyar SK, Agarwal R. Tea components: antimutagenic and anticarcinogenic effects. Prev Med 21:351-360; 1992.

Anticaries effects of polyphenolic compounds from Japanese green tea.

The dental caries inhibiting effect of the extract from Japanese green tea, one of the most popular drinks in Japan, was studied both in vitro and in vivo. The crude tea polyphenolic compounds (designated Sunphenon) from the leaf of Camellia sinensis were found to effectively inhibit the attachment of Streptococcus mutans strain JC-2 (serotype c) to saliva-coated hydroxyapatide discs. Sunphenon was also inhibitory to water-insoluble glucan formation from sucrose by crude glucosyltransferase of S. mutans JC-2 (c). Among the tea catechins tested, (-)-epigallocatechin gallate and (-)-epicatechin gallate showed the most potent inhibition of the glucosyltransferase activity. Finally, significantly lower caries scores were observed in specific pathogen free rats infected with S. mutans JC-2 (c) and fed a cariogenic diet and/or drinking water containing 0.05% Sunphenon as compared with control rats not receiving polyphenolic compounds.Otake S, Makimura M, Kuroki T, et al. Anticaries effects of polyphenolic compounds from Japanese green tea. Caries Res 25:438-443; 1991.

Monoamine metabolites, iron induced seizures, and the anticonvulsant effect of tannins.

Intracortical injections of iron ions have been shown to induce recurrent seizures and epileptic discharges in the EEG. (-)-Epigallocatechin (EGC) and (-)-epigallocatechin-3-O-gallate (EGCG), isolated from green tea leaves, have been reported to prevent or diminish the occurrence of epileptic discharges induced by iron ions, and to inhibit catechol-O-methyltransferase. Iron ions significantly increased DOPAC and HVA levels in the intrastriatal perfusate 140 and 180 minutes, respectively, after injection. EGC and EGCG inhibited the increases induced by iron ions. Furthermore, EGCG decreased the HVA level in the perfusate 200 minutes after injection whether or not iron ions were injected. Iron ions had no effect on the 5-HIAA level, and EGC and EGCG raised it. These results suggest that formation of an epileptic focus induced by iron ions might be accompanied by activation of dopaminergic neurons, and that EGC and EGCG inhibit that hyperactivity.Kabuto H, Yokoi I, Mori A. Monoamine metabolites, iron induced seizures, and the anticonvulsant effect of tannins. Neurochem Res 17:585-590; 1992.

Radioprotective effects of (-)-epigallocatechin 3-O-gallate (green-tea tannin) in mice.

Long-term administration of (-)-epigallocatechin 3-O-gallate (EGCG) to mice through drinking water prevented radiation-induced increase of lipid peroxides in liver and significantly prolonged life span after lethal whole-body X-irradiation. The result indicates validity of this green-tea component as an orally active radio-protector of very low toxicity.Uchida S, Ozaki M, Suzuki K, Shikita M. Radioprotective effects of (-)-epigallocatechin 3-O-gallate (green-tea tannin) in mice. Life Sci 50:147-152; 1992.

Platelet aggregation inhibitors in hot water extract of green tea.

The effect of hot water extract of green tea on the collagen-induced aggregation of washed rabbit platelets was examined. The extract lowered submaximal aggregation and prolonged the lag time in a dose-dependent manner. After fractionation of the extract, it was revealed that the tea catechins (tannins) are active principles for inhibition and that ester-type catechins are more effective than free-type catechins. One of the ester type catechins, epigallocatechin gallate (EGCG), suppressed the collagen-induced platelet aggregation completely at the concentration of 0.2 mg/ml (= 0.45 mM). Comparing IC50 values of EGCG and aspirin it was found that the potency of EGCG is comparable to that of aspirin. Thrombin- and platelet activating factor (PAF)-induced aggregation was also inhibited by EGCG. The elevation of cyclic adenosine 3',5'-monophosphate (cAMP) level was not observed in EGCG treated platelets. Sagesaka-Mitane Y, Miwa M, Okada S. Platelet aggregation inhibitors in hot water extract of green tea. Chem Pharm Bull (Tokyo) 38:790-793; 1990.

Antibacterial and bactericidal activities of Japanese green tea

We found that extracts of Japanese green tea leaves inhibited the growth of various bacteria causing diarrheal diseases. All tea samples tested showed antibacterial activity against Staphylococcus aureus, S. epidermidis, Vibrio cholerae O1, V. cholerae non O1. V. parahaemolyticus, V. mimicus, Campylobacter jejuni and Plesiomonas shigelloides. None of the tea samples had any effect on the growth of V. fluvialis, Aeromonas sobria, A. hydrophila, Pseudomonas aeruginosa, Salmonella enteritidis, enteroinvasive Escherichia coli, enterohemorrhagic E. coli, enteropathogenic E. coli, enterotoxigenic E. coli, Enterobacter cloacae or Yersinia enterocolitica. Salmonella and Shigella showed susceptibilities different depending on the kind of Japanese green tea. Japanese green tea showed also bactericidal activity over S. aureus, V. parahaemolyticus and even enteropathogenic E. coli which was not sensitive when tested by cup method. The bactericidal activity was shown even at the drinking concentration in daily life.Toda M; Okubo S; Ohnishi R; Shimamura T. [Antibacterial and bactericidal activities of Japanese green tea]. Nippon Saikingaku Zasshi 44:669-672; 1989.

Antimicrobial and microbicidal activities of tea and catechins against Mycoplasma

We examined tea extracts, (-) epigallocatechin gallate (EGCg) and theaflavin digallate (TF3) for their antimicrobial and microbicidal activities against Mycoplasma. Green tea and black tea showed antimicrobial activities against M. pneumoniae. At a concentration of 0.2% green tea and black tea showed microbicidal activities against M. pneumoniae and M. orale but not against M. salivarium. Extracts of pu-erh tea showed a slight microbicidal activity against M. pneumoniae and M. orale. EGCg purified from green tea and TF3 from black tea markedly showed microbicidal activities against M. pneumoniae. M. orale and M. salivarium. These results suggest that tea and catechins can be used as prophylactic agents against Mycoplasma pneumoniae infection.Chosa H, Toda M, Okubo S, et al. [Antimicrobial and microbicidal activities of tea and catechins against Mycoplasma]. Kansenshogaku Zasshi
66:606-611; 1992.

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