Two weeks have just flown by since I last posted, it really has been a combination of bad nights, bad colds and two chest infections (my son) that have occupied all my time. I know my child´s immune system is building up but I cannot help but wonder if I am doing all I can to make sure this happens. Sitting down,holding and comforting my little boy has also resulted in a lot of tea drinking. This made me consider the nutrigenomic effect of green tea.
While it is well-known that Polyphenols are powerful antioxidants, one group of polyphenols called catechins have been associated, amongst others, with immune boosting and detoxifying properties. Green tea is rich in epigallocatechin-3 galate,more commonly shortened to EGCG. Whilst there is a high level of green tea consumption is Asian cultures, the west is catching up fast with the antioxidant power of the green drink.
From a Nutrigenomic perspective, the use of green tea as a nutraceutical or functional food has shown anti-cancer potential in particular for breast cancer although more studies are needed. High levels of angiotensin II have been associated with a increased risk of breast cancer development in humans (Koh et al 2003). The angiotensin I converting enzyme (ACE) gene encodes or activates the enzyme that coverts Angiotensin I to the active angiotensin II. A low conversion rate is associated with a lower rates of breast cancer in women than those who have a high conversion rate. In those with the high activity genotype, a high consumption of green tea has resulted in a dramatic drop of a third in the risk of developing breast cancer .
The authors concluded that the antioxidant properties (particularly of the EGCG ) are protective against the Reactive oxygen species (or free radicals) generated by the high levels of Angiotensin II. No such association was made in women with the low levels of angiotensin.
Another study conducted at the University of Southern California looked at green tea ingestion and activity of the Catechol-O Methyl transferase (COMT) gene (Wu AH et al 2003a). Dr Wu´s group also found an association between green tea intake and a cancer-protective effect in those individuals with at least one copy of the low conversion COMT gene. This means that the beneficial catechins remain in circulation for longer and reduced the risk of breast cancer. It is important to note that the study was only conducted in Asian-Americans and needs to be reduced in a wider population group.
In general, gene-diet interactions identified to date have suggested that green tea may have a protective effect on carcinogens and that variations in genes associated with metabolism and/or detoxification may reduce the efficacy of green tea intervention. Meaning it may be great for some and not beneficial to others.
Irrespective of the numerous proclaimed health benefits of green tea, no claims for the use of green tea have been approved by EFSA. This outcome has not deterred consumers from enjoying the green health drink at all, and I am sure this will continue for a long time.
For health benefits, the recommended intake is 1-2 cups per day
Disclaimer: this article is based on the opinion of the author and not intended to replace medical advice.If you are considering increasing your intake of green tea, professional healthcare professional advice should be sought.
Ferguson L. Nutrigenomics Approaches to Functional foods. Journal of the American Dietetics Assoc (2009)109:452-458
Fujiki H., Ko WP.,Sun CL., Lee HP., Yu MC.Green tea intake,ACE gene polymorphism,breast cancer risk among Chinese women in Singapore.Carcinogenesis.200;26:1389-1394
Wu A.H.,Tseng Chiu-Chen.,Van den Berg David.,Yu M.C. Tea intake,COMT genotype and breast cancer in Asian-American women. Cancer Res November 1, 2003 63; 7526