Orchard Chiropractic Centre - Jersey

The Health Benefits of Green Tea

Tuesday 01 October 2019

Tea (camelia sinensis)  has been consumed in its whole, loose leaf form for thousands of years and has had many healing properties attributed to it- from boosting the immune system, improving gut health[1], oral hygiene and even reversing chronic diseases such as cancer. As a chiropractor and grower/ producer of organic whole leaf tea in Jersey, the health benefits of tea are of particular interest to me and to my colleagues at the Orchard Chiropractic Centre. 

Research into the health benefits of tea has been promising but not conclusive. In vitro studies have shown that tea is effective against a multitude of inflammatory disorders and cancers, however, the majority of in vivo research is based on epidemiological studies and small scale RCTs. The results from in vivo studies suggest that regular consumption of tea reduces the risk of cancer however, the mechanisms by which this is achieved in the living human has not been proven.

Researchers are paying particular attention to green tea as the phytochemicals (polyphenols) are present in higher concentrations in green tea compared to black tea or oolong and it is the polyphenols that are thought have the anti cancer effect[2] seen in laboratory and epidemiological studies[3].  Polyphenol consumption from green tea varies greatly from country to country and is related to green tea consumption. On average, the Japanese obtain 34% of their polyphenols from green tea . 

 

What are Polyphenols?

Polyphenols are chemicals found in plants that include: catechins, tannins and gallic acid. Leaves of camelia sinensis are rich in polyphenols but levels are reduced by processing which is why research focuses on green tea rather than black and oolong tea.

 Polyphenols have sparked particular interest in health researchers because they exhibit three mechanisms by which they can may prevent and even reverse chronic diseases such as cancer:

1)  Polyphenols  are powerful antioxidants: scavenge free radicals (very reactive oxygen species) or chelating (binding) heavy metals and toxins in the blood stream so they can be excreted

2) Polyphenols  up-regulate antioxidant enzymes;

3) Polyphenols can also be pro oxidants: producing hydroygen peroxide and super oxide which have been shown to cause apoptosis in cancer cells.

When polyphenols such as tannins and gallic acid are combined they act synergistically enhancing the potency of their effect. Whilst this is easily observable in laboratory studies, their complex interactions with other chemicals and reactions within the human body continue to prove difficult to study.

 

Polyphenols present in green tea include:

  • Gallic acid

  • Gallocatechin

  • Catechin

  • Epicatechin

  • Epigallocatechin

  • Epicatechin gallate

  • Epigallocatechin gallate

  • p-coumaroylquinic acid

  • Gallocatechin3 gallate

 

Catechins

Catechins are the most active antioxidants in green tea. They also contribute to the taste and strength of the tea. Being antioxidant, catechins scavenge free radicals and may therefore prevent cell damage and cancers.

Epigallocatechin-3-gallate "EGCG" (a compound of epigallocatechin and gallic acid) is a particular catechin that is attracting significant attention from researchers. It is a powerful anti inflammatory and pro oxidant. It is also the most abundant polyphenol in green tea by weight which is thought to be why green tea can induce apoptotic cell death in cancer cells[4].

Tannins are found in plant sources such as bark, fruit skins, seeds and tea leaves. they are potent antioxidants - protecting cells from the effects of free radicals and have anti microbial, anti viral, anti fungal and anti inflammatory properties.  The ability to prevent inflammation and gene mutation may be a mechanism by which tannins can protect against some cancers

Gallic acid- also an anti oxidant, provides protection from free radical damage, has anti inflammatory and anti fungal properties. Gallic acid is well known for its anti fungal properties. It protects against aflatoxins produced by fungi during storage and is therefore used by the food industry to preserve wheat, corn and nuts. Its anti fungal properties are also beneficial to the human gut when consumed.

 

The Evidence

The antioxidant properties of catechins and therefore their possible ability to prevent some cancers has ignited interest in these compounds.

 According to a 2011 study by Forester and Lambert, most of the in vivo evidence is based on epidemiological studies, citing an inverse association between green tea consumption and lung cancer in smokers but not non-smokers. This suggests that green tea consumption may be important in high risk groups. This was also the case with women with a genetic predisposition to breast cancer.

Another study[5]  involving  sixty volunteers with High-Grade Prostate Intraepithelial Neoplasia (which has a 30% chance of developing into prostate cancer within 1 year) treated 30 men with green tea catechins ("GTC") and 30 with placebo. After 1 year only one tumour (incidence~3%) was found in the group treated with GTC compared to nine (incidence 30%) in the placebo group.

Laboratory studies indicate that the anti cancer properties of EGCG are likely mediated through antioxidant or pro-oxidant mechanisms:

a) by inhibiting enzymes involved in cell replication and DNA synthesis; and

b) via production of hydrogen peroxide causing apoptosis.

Forester and Lambert (2011)[6] referred to one study that suggests that selenium could enhance the anticancer activity of green tea.

 

Conclusion

In vitro studies clearly show that green tea polyphenols have anti inflammatory and anti cancer properties. These disease preventing and disease reversing properties have also been documented in small scale in vivo studies, but larger studies are required. Whether or not the mechanisms of disease prevention documented in the laboratory are replicated in the human body also remains to be proven. However, epidemiological studies suggest that green tea consumption is beneficial in disease prevention and in particular, those in high risk groups.   

 

 

 

 

 



[2] Fajun Yang, Willem J. S. de Villiers, Craig J. McClain, Gary W. Varilek, Green Tea Polyphenols Block Endotoxin-Induced Tumor Necrosis Factor-Production and Lethality in a Murine Model, The Journal of Nutrition, Volume 128, Issue 12, December 1998, Pages 2334–2340, https://doi.org/10.1093/jn/128.12.2334

[3] Forester SC, Lambert JD. The role of antioxidant versus pro-oxidant effects of green tea polyphenols in cancer prevention. Mol Nutr Food Res. 2011;55(6):844–854. doi:10.1002/mnfr.201000641

[4] Forester SC, Lambert JD. The role of antioxidant versus pro-oxidant effects of green tea polyphenols in cancer prevention. Mol Nutr Food Res. 2011;55(6):844–854. doi:10.1002/mnfr.201000641

[5] Chemoprevention of Human Prostate Cancer by Oral Administration of Green Tea Catechins in Volunteers with High-Grade Prostate Intraepithelial Neoplasia: A Preliminary Report from a One-Year Proof-of-Principle Study Saverio Bettuzzi, Maurizio Brausi, Federica Rizzi, Giovanni Castagnetti, Giancarlo Peracchia and Arnaldo Corti Published January 2006

[6] Forester SC, Lambert JD. The role of antioxidant versus pro-oxidant effects of green tea polyphenols in cancer prevention. Mol Nutr Food Res. 2011;55(6):844–854. doi:10.1002/mnfr.201000641


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