Green and Black Tea in Good Health

By James Collier BSc (Hons), MT Co-Owner and Nutrition Consultant www.healthyaction.co.uk
December 2011

After water, the most consumed beverage in the world is tea in one form or another. Tea has been shown to offer a range of natural health benefits largely due to its flavonoid content (30% of dry weight). Media attention often focuses on green tea having the real benefits, but as all tea comes from the same plant, Camellia sinensis, in theory, all types should have similar health benefits (1) and have similar total polyphenol contents (2). The key polyphenols in tea are flavonoid tannins.

Worldwide Tea Production
Black / regular 78%
Green 20%
Oolong (traditional Chinese) 2%

Flavonoids
Tea leaves undergo different processes to make green and black teas and this impacts on the flavonoid content. Green tea is made by the leaves being withered, then steamed or pan fired, before being rolled and then dried. The black tea leaf making process involves and additional step of aeration of the cut, withering leaves for several hours which oxidises the flavonoids as well as darkening the leaves' colour.

Overall flavonoid levels are similar, but green tea contains more catechins: 80-90% compared to 20-30% in black tea, as well as more theaflavins and thearubigins (3). Green tea also has a lower caffeine level (40mg per typical serving) than black tea (50mg per serving); (for comparison instant coffee is around 80-90mg per serving).

Cardiovascular Health
There have been a large number of studies looking at tea and cardiovascular health. For green tea, epidemiological studies have suggested a reduced risk of heart disease and stroke at intakes of 5-6 cups per day. Also, studies looking at risk with use of green tea extract supplements have shown a significant risk reduction (4). Green tea catechins are believed to exert their protective element by inhibiting oxidation, reducing blood lipids, regulating vascular tone, preventing inflammation and suppressing platelet adhesion (5).

However, the effects of black tea are not dissimilar with intakes of just 2-3 cups per day showing a significant reduced risk of CV disease in some well designed trials (6,7,8,9). There have even been a few studies which have compared the effects of green and black tea and the results have been shown to be similar for both (6,10,11).

Diabetes
There is limited but significant evidence which shows that tea consumption is asscoaited with reduced risk of type 2 diabetes (12,13). This may be due to the theaflavins modulating plasminogen activator inhibitor function, which has been shown to play a role in reduce risk of diabetes risk.

Cancer
The evidence for tea consumption reducing risk of types of cancers is weak and the studies are few and far between. However, the theory of a mechanism of action is there, i.e. the antioxidant effects and this could be apparent in reducing risk of bowel cancer, perhaps due to the effect of flavonoids in the large intestine (14).

Dental Health
Tea has anti-bacterial properties and it's been shown to inhibit Strep. Mutans, the species responsible for dental caries, by reducing the adhesion of bacteria to the teeth. Tea may also inhibit the production of the enzyme salivary amylase which breaks down starch in the mouth. Evidence suggests that regular tea consumption lowers the risk of caries and that thearubigins appear to offer the best effects (15,16). Tea is often consumed with milk and milk does have it's own anti-cariogenic effects due to mineral content.

Weight Control
Green tea extract has been shown to be beneficial in weight control. The key constituents here are the catechins, especially epigallocatechin gallate (EGCG) which has been shown to be the most powerful of the catechins. Catechins are flavonoids and antioxidants, but have also been shown to be lipolytic (fat burning) independent of caffeine by increasing thermogenesis and 24-hour energy expenditure and fat oxidation (17). Black tea does contain catechins but at lower levels than green tea. Catechins may also have a small stimulatory effect, by inhibiting noradrenalin degradation.

When you see green tea extract supplements, the primary ingredient is EGCG and these supplements have also been marketed as an inhibitor of the digestive enzyme lipase, thereby reducing fat digestion and absorption, but there is no basis for this claim in any way, and it is another example of unsound marketing by manufacturers. However, as a thermogenic aid and fat oxidiser, green tea extract is effective and may have a use in bodybuilding, for keeping body fat levels down.

Bioavailability
Although the absorption of tea flavonoids is generally lower due to their molecular weight, the popularity of tea makes it one of the most important sources of flavonoids ion the diet, providing up to 80% of flavonoid consumption in some nations (18). There has been debate as to whether the addition of milk to tea adversely affects flavonoid absorption due to the binding with milk proteins, but the results are inconclusive.

Green Tea vs. Black Tea
There is a deal of cultural differences in tea consumption, and the UK average consumption of black tea is 2.3 mugs per day (19). In contrast, there is no reliable consumption estimates for green tea as it remains a niche benefit. Green tea is marketed as a very 'healthy' drink – which, of course, it is – and is seen as a more fashionably healthy alternative to black tea. In respect of active antioxidant content, green tea is slightly higher, but this could be because of the oxidised tannins during the production of black tea, or due to the fact that typically we leave the bag to stew for longer in green tea than we typically do in black. Catechin, especially EGCG, levels are higher in green tea so its fat burning properties are higher. However, the evidence of black tea vs. green tea when looking at disease prevention is very similar.

Black and green teas appear to offer similar health benefits at intakes of 4-6 cups per day. Also, don't get too wrapped up in all the above benefits of tea and at the expense of forgetting its most fundamental contribution to a bodybuilder's nutrition: fluid.


References:
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  2. Obuchowicz J et al (2011). Flavonol database for green and black teas utilising ISO 14502-1 and ISO 14502-2 as analytical tools. J Food Comp Anal (in press)
  3. Deka A & Vita JA (2011). Tea and cardiovascular disease. Pharm Res 10
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  17. Dulloo AG; et al. (1999). Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr 70: 1040-1045
  18. Song WO & Chun OK (2008). Tea is the major source of flavan-3-ol and flavonol in the US diet. J Nutr 138: 1543S-1547
  19. Henderson L et al (2002). National Diet and Nutrition Survey: adults aged 19-64 years. FSA: London