Tea For Your Health – January 2014
Update for Health Professionals & Media – January 2014
In this issue:
- What is tea?
- An overview of Research on the Potential Health Benefits of Tea
- Flavonoid content of beverages
What is tea?
All tea is derived from one bush plant called Camellia sinensis. The first cup of tea was discovered by Chinese Emperor Shen Nung in 2737 B.C., when a tea leaf accidentally fell into the bowl of hot water he was drinking. Today tea is the world’s most popular prepared drink.
There are so many varieties of tea available today but it all starts with the tea leaf that is handled differently after harvesting to produce uniquely different types of teas including white, green, oolong, black or pu-erh tea. The key to different types of teas lies in the level of the tea’s oxidation.
To simplify the stages of the tea production process we provided the Tea Leaf Oxidation chart below. For example, Green Tea is produced by heating leaves shortly after harvesting to prevent oxidation, and then rolling the dry leaves. Black and Oolong Tea undergo full or partial oxidation respectively, which makes the leaves – and subsequent brew – darker in colour.
“Herbal tea” is made from herbs, spices, and fruit and is not technically a tea since it is not derived from the Camellia sinensis plant. Herbal teas are infused drinks referred to by tea experts as a “tisane.”
How Tea Works in the Body
Tea contains hundreds, if not thousands, of bioactive compounds including amino acids, caffeine, lignin’s, proteins, xanthines and flavonoids. Tea flavonoids and the related polyphenols account for more than one third of the weight of tea leaves; the health benefits of the are most often attributed to tea flavonoids. 1
The flavonoid content of tea depends on many factors including the type and amount of tea used and the length of time it is steeped. Flavonoids are antioxidants found in many fruits and beverages, but are particularly abundant in tea.
Flavonoid content in selected beverages 2
Tea flavonoids are bioactive compounds that have specific cellular targets that are related to the cardiovascular, metabolic and other health benefits. 1 Recent research has explored the potential health attributes of tea through human clinical trials, population- based studies, and in vitro laboratory research.
Additional research suggests tea flavonoids and related bioactive compounds in tea may play important roles in various areas of healthy and may operate through a number of different mechanisms under exploration.
Tea’s Role in Heart Health
Human population studies have found that people who regularly consume 3 or more cups of Black tea per day have a reduced risk of heart disease and stroke.3,4 Clinical studies suggested that the risk reduction associated with tea consumption may be due to improvement in some risk factor for cardiovascular disease, including blood vessel function, platelet function and a reduction in oxidative damage.5,6
While researchers are still examining the various mechanisms by which tea flavonoids function, some studies suggest multifunctional mechanism that work in tandem to improve markers for cardiovascular health. Important areas of tea and cardiovascular health research include blood vessel and endothelial function, serum cholesterol levels and low density lipoprotein (LDL) cholesterol oxidation.5,6,8 Each of these factors impacts the risk of myocardial infarction (heart attacks) stroke and cardiovascular disease.
Tea’s Role in Brain Health
Age- related declines in memory and cognition occur naturally, but research suggests that modifiable factors, such as diet and exercise may help slow the progression of age-related neurodegeneration. Research indicates recommendations to improve hear and cardiovascular function are also neruoprotective.9,10
The benefits of tea that help improve biomarkers for reducing the risk of heart disease may improve brain health too. The bioactive compounds found in tea may promote nerurological health through various actions.11,12 In addition, L-theaninne in tea has been shown to directly affect areas of the brain that control attention and abilty to solve complex problems.13
Tea’s Role in Healthy Body Weight
Several studies suggest drinking calorie-free tea may help with weight management.14,15,16 A recent study identified a correlation between hot tea consumption and lower mean waist circumference and lower BMI among adult tea drinkers vs non-tea drinkers.14 Preliminary research suggests that tea flavonoids help elevate metabolic rate, increase fat oxidation and improve insulin activity.15,17
- Balentine D, et al. The chemistry of tea flavonoids. Crit Rev Food Sci Nutr. 1997; 37:693-704
- Source: USDA database for flavonoid content of selected foods (2007)
- Larsson SC, et al. Black tea consumption and risk of stroke in women and men. Ann Epidemiol 2013 Mar, 23(3):157-60
- Arab L, et al. Green and Black Tea Consumption and Risk of Stroke. A Meta-Analysis. Stroke 2009;40(5):1786-92
- Aggio A, et al. Endothelium/nitric oxide mechanism mediates vasorelaxation & counteracts vasoconstriction induced by low concentration of flavanols. EJN 2012
- Grassi D, et al. Black tea consumption dose-dependently improves flow-mediated dilation in healthy males. J Hypertens 2009, 27:774-781.
- Hertog MGL, et al. Dietary antioxidant flavonoids and risk of coronary artery disease the Zutphen Elderly Study Lancet 1993;342:1007-11
- Hofmann CS, et al. Green tea polyphenol epigallocatechin-3 gallate induces apoptosis of proliferating vascular smooth muscle cells via activation of p53. FASEBJ.2003 Apr; 17(6):702-4. Epub 2003 Feb 05.
- Scarmeas N, et al. Physical activity, diet, and risk of Alzheimer disease. JAMA 2009 Aug 12;302:627.
- Alzheimer’s Association. (n.d.) Prevention and Risk of Alzheimer’s and Dementia: Heart-Head Connection. Retrieved from http://www.alz.org/research/science/alzheimers_prevention_and_ris.asp#heart
- Mandel SA, et al. Targeting multiple neurodegenerative disease etiologies with multimodal-acting green tea catechins. J Nutr 2008;138:1578S-83S
- Egashira N, et al. Theanine prevents memory impairment induced by repeated cerebral ischemia in rats. Phytother Res. 2007 Aug 17 [Epub ahead of print]
- Kelly SP, et al. L-Theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. J Nutr 2008;138:1572S-7S
- Vernarelli JA, et al. Tea consumption is inversely associated with weigh status and other markers for metabolic syndrome in US adults. Eur J Nutr. 2013Apr;52(3):1039-48. Epub 2012 Jul 10.
- Hursel R, et al. The effects of green tea on weight loss and weight maintenance: a meta-analysis. Int J Obes (Lond). 2009 Sep:33(9):956-61. Epub 2009 Jul14.
- Nagao T, et al. Ingestion of a tea rich in catechins leads to a reduction in body fat and malondialdehyde-modified LDL in men. AmJClin Nutr 2005 Jan:81(1):122-9.
- Murase T, et al. Green tea extract improves running endurance in mice by stimulating lipid utilization during exercise. Am J Physiol Regul Integr Comp Physiol. 2006 Jun:290(6):R1550-6.
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