Doc:Tea

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Classification 分類

green tea
It is non-fermented, i.e., produced by drying an steaming the fresh leaves of Camellia sinensis var. sinensis to inactivate polyphenol oxidases.
oolong tea
It is produced by partial fermentation before drying.
black tea
It is fully fermented by oxidation.
red (pu-erh) tea
It is fully fermented by microorganisms including Aspergillus spp. and Penicillium spp.

Per capita mean consumption of tea in the world is 120 mL/day [1], the second most consumed beverage in the world (next to water). Black tea is principally consumed in Western countries, green tea is popular in Asia, and oolong tea in China and Taiwan[2]. 世界における茶の一人当たり消費量は 120 ml/日 [1]で、世界で飲まれる飲料ナンバー２です。紅茶は主に西洋で飲まれ、緑茶はアジア、ウーロン茶は中国と台湾で飲まれます[2]。

Composition

Catechins

The major phenolics in green tea include catechins (flavan 3-ols). They are (-)-epigallocatechin-3-gallate (EGCG; 59% of total catechins), (-)-epigallocatechin (EGC; 19%), (-)-epicatechin-3-gallate (ECG; 13.6%), and (-)-epicatechin (EC; 6.4%) [1]. Catechins are converted to theaflavins and thearubigins in black tea [3]. A cup of tea may contain 90 mg of EGCG [2], but in human, EGCG is less bioavailable (i.e. little absorbed) than other green tea catechins. However, the bioavailability is different between species and genotypes [4][5].

After drinking tea, the plasma level of catechins reach their peaks (between 1-10 µmol/L) in 2 - 4 h [6]. After 24 h, plasma levels of EGCG and EGC return to baseline, but that of ECG remains elevated in methylated forms[7].
カテキン

緑茶中の主なフェノール化合物はカテキン(フラバン3-オール)で、(-)-エピガロカテキン-3-ガレート (EGCG; 全カテキンの59%), (-)-エピガロカテキン (EGC; 19%), (-)-エピカテキン-3-ガレート (ECG; 13.6%)そして(-)-エピカテキン (EC; 6.4%) [1]です。 紅茶ではカテキンはテアフラビンとテアルビジンに変換されます[3]。 コップ１杯のお茶にはおよそ90 mgのEGCG [2]が含まれますがEGCGは他の茶カテキンに比べ、ヒト体内にあまり吸収されません。 生物学的な利用能力は生物種や遺伝型によって変化します[4][5]。

お茶を飲んだ後、血漿中のカテキン濃度は2-4時間でピーク（1-10 µmol/L)に達します[6]。 24時間後には血漿中のEGCG, EGCは初期値に戻りますが、ECGはメチル化された形で残っています[7]。

Major Composition (%)[8]
Compound Green tea Black tea Black tea
Infusion (3min)
Proteins 15 15 trace
Amino acids 4 4 3.5
Fiber 26 26 0
Others, carbohydrates 7 7 4
Lipids 7 7 trace
Pigments 2 2 trace
Minerals 5 5 4.5
Phenolic compounds 30 5 4.5
Oxidized phenolics 0 25 4.5
Caffeine

The caffeine content in different types of tea is: black tea > oolong tea > gree tea > fresh tea leaf [9]. More than 200 mg/day caffeine is not advisable and may produce nervousness, sleep disorders, vomits, headaches, epigastric pain, and tachycardia [10].

カフェイン

異なる茶に含まれるカフェインの量は 紅茶＞ウーロン茶＞緑茶＞新鮮な茶葉[9]となります。 200 mg/日以上のカフェイン摂取は、イライラ、不眠、吐き気、頭痛、胃痛や頻脈を引き起こすので薦められません[10]。

Caffeine Content in Beverages[11]
Product content (mg /150mL) Product content (mg /150mL)
espresso coffee 108-180 normal coffee 80-115
instant coffee 65 black tea (3min brew) 40-70
oolong tea 18-33 iced tea 29
green tea (3min brew) 15-25 cola soft drink 15-19
hot chocolate 4 cocoa milk shake 3
decaffeinated coffee 1-3 decaffeinated tea 0.6-3
plain chocolate 15 mg/20g milk chocolate 5 mg/20g
References
  1. ↑ 1.0 1.1 1.2 1.3 McKay DL, Blumberg JB (2002) "The role of tea in human health: An update" J Am Coll Nutr 21:1-13
  2. ↑ 2.0 2.1 2.2 2.3 Wu CD, Wei GX (2002) "Tea as a functional food for oral health" Nutrition 18(5):443-444
  3. ↑ 3.0 3.1 USDA Database for the Flavonoid Contents of Selected Foods, Beltsville 2003
  4. ↑ 4.0 4.1 Kim S, Lee MJ, Hong J (2000) "Plasma and tissue levels of tea catechins in rats and mice during chronic consumption of green tea polyphenols" Nutr Cancer 37:41-48
  5. ↑ 5.0 5.1 Loktionov A, Bingham S et al. (1998) "Apolipoprotein E genotype modulates the effect of black tea drinking on blood lipids and blood coagulation factors: A pilot study" Br J Nutr 79:133-139
  6. ↑ 6.0 6.1 Yang CS, Chen L et al. (1998) "Blood and urine levels of tea catechins after ingestion of different amounts of green tea by human volunteers" Cancer Epidemiol Biomarkers Prev 7:351-354
  7. ↑ 7.0 7.1 Higdon JV, Frei B (2003) "Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions" Crit Rev Food Sci Nutr 43:89-143
  8. ↑ Belitz DH, Grosch W (1997) "Quimica de los Alimentos" Zaragoza Acribia
  9. ↑ 9.0 9.1 Lin Lin YS, Tsai YJ et al. (2003) "Factors affecting the levels of tea polyphenols and caffeine in te a leaves" J Agric Food Chem 51:1864-1873
  10. ↑ 10.0 10.1 Varnam AH, Sutherland JP (1994) "Beverages: Technology, Chemistry and Microbiology" Chapman & Hall (London)
  11. ↑ Cabrera C, Artacho R, Gimenez R (2006) "Beneficial Effects of Green Tea-A Review" J Am Coll Nutr 25(2):79-99

Human Health

Cancer 癌

As below, none of the large-scale epidemiological studies showed a significant association of tea intake with a lower risk of cancer[1]. However, many case-control studies and cross-sectional studies (up to several hundreds people) show a decrease of the risk of cancer.

  • Breast cancer 乳がん
Two prospective studies with 35,004 women [2] → no association
  • Gastrointestinal cancer 胃腸がん
Prospective cohort 14873 men and 23667 women [3] → no association
Prospective cohort 11902 men and 14409 women [4] → no association
Prospective cohort 30370 men and 42481 women [5] → no association
Prospective cohort 18746 men and 26184 women [6] → no association
  • Bladder cancer 膀胱がん
Prospective cohort 14873 men and 23667 women [3] → no association
  • Cancer incidence がん
Prospective study 38540 people [3] → no association
References
  1. ↑ Borrelli F, Capasso R et al. (2004) "Systematic review: green tea and gastrointestinal cancer risk" Aliment Pharmacol Ther 19:497-510
  2. ↑ Suzuki Y, Tsubono Y et al. (2004) "Gren tea and the risk of breast cancer: pooled analysis of two prospective studies in Japan" Br J Cancer 90:1361-1363
  3. ↑ 3.0 3.1 3.2 Nagano J, Kono S et al. (2001) "A prospective study of green tea consumption and cancer incidence, Hiroshima and Nagasaki (Japan)" Cancer Causes Control 12:501-508
  4. ↑ Tsubono Y, Nishino Y et al. (2001) "Green tea and the risk of gastric cancer in Japan" New Engl J Med 344:632-636
  5. ↑ Hoshiyama Y, Kawaguchi T et al. (2002) "A prospective study of stomach cancer death in relation to green tea consumption in Japan" Br J Cancer 87:309-313
  6. ↑ Fujino Y, tamakoshi A et al. (2002) "Prospective study of education background and stomach cancer in Japan" Prev Med 35:121-127

Cardiovascular Disease (CVD) 循環器疾患

After Hertog MG et al.[1], flavonoid intakes have been reported to inversely associated with CVDs. In 2008, Hooper et al. performed a comprehensive review of 133 flavonoid trials[2], and concluded that

  • flavanol-rich cocoa reduces blood pressure by 6 (systolic) and 3 (diastolic) mm Hg,
  • soy protein, which is rich in isoflavones, reduces LDL cholesterol by 0.2 mmol/L,
  • black tea acutely (not chronic) raises blood pressure by 6 (systolic) and 3 (diastolic) mm Hg, and
  • chocolate acutely (not chronic) increases flow-mediated dilation (FMD) by 4%.
At least, flavonoid-rich foods provide evidences for beneficial effects on CVD. However, it remains unclear whether the effects can be attributed to the specific flavonoid species. A large scale cohort study (34789 men) found no association with flavonoids and CVD [3].


References
  1. ↑ Hertog MG, Feskens EJ (1993) "Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study" Lancet 342(8878):1007-1011
  2. ↑ Hooper L, Kroon PA, Rimm EB, et al. "Flavonoids, flavonoid-rich foods, and cardiovascular risk: a meta-analysis of randomized controlled trials" Am J Clin Nutr 88:38–50
  3. ↑ Rimm EB, Katan MB (1996) "Relation between intake of flavonoids and risk for coronary heart disease in male health professionals" Ann Intern Med 125(5):384-389

Obesity 肥満

Recently, resveratrol is also found to improve obesity.[1].


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