Doc:Tea/Health

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Tea Top Exotic teas Production/Consumption Health

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Tea and Human Health

Cancer

None of the large-scale epidemiological studies found 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 PMID 14987318
  2. Suzuki Y, Tsubono Y et al. (2004) "Green tea and the risk of breast cancer: pooled analysis of two prospective studies in Japan" Br J Cancer 90:1361-1363 PMID 15054454
  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 PMID 11519758
  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 PMID 11228277
  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 PMID 12177800
  6. Fujino Y, tamakoshi A et al. (2002) "Prospective study of educational background and stomach cancer in Japan" Prev Med 35:121-127 PMID 12200096

Cardiovascular Disease (CVD)

It is often believed that (oolong) tea possesses hypotensive effects. 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 reliable 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, intake of cocoa and soy (not tea!) provide evidence for short-term beneficial effects on CVD. However, it remains unclear whether the effects can be attributed to the specific flavonoid species [3]. A large scale cohort study (34789 men) found no association with flavonoids and CVD [4] [5].

  1. Hertog MG, Feskens EJ (1993) "Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study" Lancet 342(8878):1007-1011 PMID 8105262
  2. Hooper L, Kroon PA, Rimm EB, et al. (2008) "Flavonoids, flavonoid-rich foods, and cardiovascular risk: a meta-analysis of randomized controlled trials" Am J Clin Nutr 88:38–50 PMID 18614722
  3. Geleijnse JM, Hollman PCH (2008) "Flavonoids and cardiovascular health: which compounds, what mechanisms?" Am J Clin Nutr 88:12-13 PMID 18614717
  4. 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 PMID 8702089
  5. Huxley RR, Neil HA (2003) "The relation between dietary flavonol intake and coronary heart disease mortality: a meta-analysis of prospective cohort studies" Eur J Clin Nutr 57:904–908 PMID 12879084

Hypercholesterolemia

In many animal studies, usually rats, various tea suppresses cholesterol levels. Catechins are considered to account for the hypocholesterolemic effect.

  • Lower plasma triacylglycerols, cholesterol, and low-density lipoprotein (LDL) cholesterol in experimental Sprague-Dawley rats [1].
  • Lower serum and liver cholesterols, but not HDL-cholesterol and triglyceride levels in rats. [2]

  1. Kuo KL, Weng MS, Chiang CT, Tsai YJ, LinShiau SY, Lin JK (2005) Comparative studies on the hypolipidemic and growth suppressive effects of oolong, black, pu-erh and green tea leaves in rats. J Agric Food Chem 53:480-489
  2. Yang TT, Koo MW (1997) Pharmacol Res 35(6):505-512


Obesity

Recently, resveratrol is found to improve obesity.[1]. Some studies suggest relationship between green tea consumption and reduction in body fat[2][3], but clear evidence on body weight control is missing. Since body weight may change for various reasons, it is hard to conduct an epidemiologic study.

  1. Baur JA et al. Sinclair DA (2006) "Resveratrol improves health and survival of mice on a high-calorie diet" Nature 444:337-342
  2. Wu CH, Lu FH et al. (2003) "Relationship among habitual tea consumption, percent body fat, and body fat distribution" Obes Res 11:1088-1095
  3. Tian WX, Li LC et al. (2004) "Weight reduction by Chinese medicinal herbs may be related to inhibition of fatty acid synthase" Life Sci 74:2389-2399
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