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Black tea and cardiovascular disease. International Journal of Epidemiology 2005 34(2):482-483 (2005).
Extract: Potential protective effects of black tea against cardiovascular disease and cancer are attributed to polyhenol compounds and flavonoids/flavonols, including catechin/EGCG and theaflavin. The authors admit that they lacked a data-based approach for selecting foods/beverages contributory to certain nutrients in order to assess intake of flavonols/theaflavins from black tea.
We can assume from the literature that black tea is a major source of catechin/EGCG, but comparisons within several cups of black tea may not have enough power to detect any favourable effects of catechin/EGCG. In other words, a dose–response relationship could not be proven even after taking into account confounding coffee consumption. Although thus far inconsistent, some beneficial effects have been experienced with large intakes of black/green tea, such as ≥10 cups/day. We need a wide range of comparisons for cups of black tea to evaluate possible protective effects, if any, on cardiovascular disease.
The concentrations of catechin/EGCG in black tea are rather less than in green tea. In addition, antioxidant activity of black tea scored by oxygen radical absorbing capacity (ORAC) is lower than that for green tea. Furthermore, flavenoids are supplied to a greater extent by vegetables and fruit than several cups of black tea. Thus the authors should, at least, adjust for effects of consumption of vegetables and fruit.
Finally, it is known that folate is antiangiogenic because it is a cofactor in the metabolism of homocysteine to methionine. According to our recent study,9 folate is supplied by green tea along with vegetables and fruit; however, its content in black tea is far less than in green tea. Black tea thus seems generally less anticarcinogenic, antimutagenic, and antiangiogenic than green tea. Moreover, any fluids/beverages, including water, black/green tea, and coffee, may be important in terms of blood viscosity and excretion/dilution of mutagenic and carcinogenic substances.
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Here is a general rationale that is easily applied for distinguishing the general redox buffering of a food or beverage. The more processed and oxidized it is, the higher the reducing equivalents necessary to convert 'antioxidants' to it's beneficial (reduced) form in your cells.
Every antioxidant needs its redox 'couple' (partner) to convert it back to its reduced state after it 'does it's thing' and reduces an oxidant that can damage nucleic acids, membranes or proteins in cells. This is just as true for vitamin C, E, and other antioxidants as it is tea polyphenols.
Secondly, many antioxidant species in black teas have reacted with nearby plant cell wall constituents to form larger phenolic complexes that react with oral cavity receptors, contributing to the complex flavors of black and oolong teas. These fermentation complexes (theaflavins and thearubigens) appear to have health benefits of their own with respect to cardiovascular disease and stroke risk.
Your best bet is to mix it up, drinking both green and black teas, and making sure you include at the very least 5-8 servings of fruits and vegetables in your daily diet.
Protective beneficial effects of improved antioxidant intake can be evident in as little as a few weeks, once dietary changes are made, especially if they precede the adoption of daily physical exercise and are accompanied by adequate sleep (correct sleep hygiene includes quality AND quantity of sleep at appropriate hours) and de-stressing techniques.