The wonders of green tea

The health benefits of green tea have been the subject of extensive clinical research. Green tea in particular, contains the antioxidant catechin which has many biological functions. Indeed, this puported wonder tea has been suggested to have anti-cancer effects (1,2) by suppressing tumour promotion (3), an ability to reduce cardiovascular disease risk (4) and reduce inflammation associated with rheumatoid arthritis (5).

As this type of tea is subject to minimal processing, this means a large portion of the catechin content is unchanged.  The catechins are found in many forms but the one researchers become most excited about is epigallocatechin-3-gallate (EGCG), which is the most effective at eliminating free radicals. Generally studies support a moderate intake of green tea of 3 to 4 cups (6), where one cup contains approximately 90 mg EGCG (7). Bear in mind decaffeinated, instant and iced green teas will contain less catechins (8).


Other properties of green tea include caffiene. The caffiene content of green tea varies from 15 to 25mg per 150ml (as a comparison, instant coffee has double this amount*). Consumption of which has been linked to effects such as increased fat oxidation and increased energy expenditure. However, trials exploring these effects have found participant weight loss to be minimal and often the quality of the studies is questionable.

For a more comprehensive overview of the findings from green tea studies to-date, Today's Dietitian provides an interesting insight.

Link to article in Today's Dietitian

Ultimately, the jury is out on whether the health benefits of green tea have as far reaching effects as claimed. However, my personal opinion is that green tea, in it's best form as loose leaf, provides a healthy alternative to hydration and stimulation (from caffiene) compared to alternative sugary hot and cold drinks, with some added antioxidants for good measure!

From experience, it is best to have something to eat before drinking green tea as as it may make you nauseous on an empty stomach. And ideally, try to leave half and hour before and after meals when drinking tea, to ensure that it does not reduce the absorption of iron from your food.  If you are new to green tea, you may enjoy green tea infused with flavours such as lemon or jasmine.

Enjoy!

*Large amounts of caffiene (>200mg) are not advised in pregnancy. See NHS Choices link for more details.

References:
1. Brown, M. D. (1999). Green tea (Camellia sinensis) extract and its possible role in the prevention of cancer. Alternative Medicine Review, 4(5), 360-370.
2. Chen, D., Daniel, K. G., Kuhn, D. J., Kazi, A., Bhuiyan, M., Li, L., … Dou, Q. P. (2004). Green tea and tea polyphenols in cancer prevention. Frontiers in Bioscience, 1(9), 2618-31. 2004
3. Fujiki, H., Suganuma, M., Okabe, S., Sueoka, E., Suga, K., Imai, K., ...Nakachi K. A new concept of tumor promotion by tumor necrosis factor-alpha and cancer preventive agents (-)-epigallocatechin gallate and green tea--a review. Cancer Detectection and Prevention, 24(1), 91-99.
4. Kuriyama, S., Shimazu, T., Ohmori, K., Kikuchi, N., Nakaya, N., Nishino, Y., … Tsuji, I. (2006). Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA, 296(10), 1255-65.
5. Singh, R., Akhtar, N., & Haqqi, T. M. (2010). Green tea polyphenol epigallocatechin-3-gallate: inflammation and arthritis. Life Science, 86(25-26), 907-918
6. Mehrar & Baker as cited in Karak, T., & Bhagat, R. M. (2010). Trace elements in tea leaves, made tea and tea infusion: A review. Food Research International, 43, 2234-2252.
7. Wu, C. D. &, Wei, G. X. (2002). Tea as a functional food for oral health. Nutrition, 18, 443–444.
8. Arts et al. as cited in Cabrera, C., Artacho, R., & Gime´nez, R. (2006). Review: Beneficial Effects of Green Tea—A Review. Journal of American College of Nutrition, 25(2), 79-99.





 

---