Where did it all start?

Green tea originated in China and is thought to date back some 3000 years when the leaves were first chewed and eaten. Later on they were brewed and consumed as a tea and Buddhist monks returning from China introduced the tea to Japan as an elixir for long life. Fast forward to the present day and green tea is still in demand, with an ever increasing body of knowledge supporting its benefits.

 

Potent polyphenols

Green tea is produced by steaming fresh leaves from the Camellia sinensis bush at high temperatures. This process inhibits oxidation of the leaves, retaining a diversity of beneficial polyphenols, whose combined activity is thought to be responsible for the tea’s many health benefits.

Polyphenols are compounds found in a variety of foods that have been linked to a reduced risk of chronic diseases. Green tea contains about 30% polyphenols by weight and these include large amounts of compounds known as catechins, the most notable being epigallocatechin gallate (EGCG) which exerts potent anti-inflammatory and antioxidant activity, helping to protect cells from free radical damage and supporting the body’s own antioxidant defence systems. Free radical damage is believed to play a role in the development of many diseases and the ageing process.

 

How about the research?

‘An ever-growing body of research supports the beneficial properties of green tea.’

  • A large-scale population study in Japan suggests that consuming three or more cups of green tea daily may significantly decrease the risk of cardiovascular and all-cause mortality compared to drinking less than one cup daily. Interestingly, this association appeared to be stronger in women than men.

  • Another study, published in the American Journal of Clinical Nutrition suggests that green tea extract might be useful for the heart health of post-menopausal women. Daily supplementation for 12 months was shown to reduce circulating total cholesterol and LDL-cholesterol levels.

 

 

One aspect of green tea’s benefits that has attracted a lot of interest over recent years is its potential for fat burning and weight loss. Various studies have considered different catechin and caffeine-rich teas, including green tea, as a useful means of maintaining or enhancing energy expenditure and increasing fat oxidation. This is because green tea boosts metabolism and it is thought that the tea polyphenols may help to counteract the lowered metabolic rate that usually occurs after weight loss.

Whilst this could be particularly beneficial for weight maintenance once the pounds have been shed, research suggests that other factors may come into play here, such as an individual’s genetic predisposition, their habitual caffeine intake, and the catechin composition and dose of the tea they are drinking.

Green tea may also be helpful if you suffer from joint problems as the polyphenols seem to lessen joint degeneration in laboratory models of rheumatoid arthritis. It is thought that the EGCG may block the production of molecules that cause joint damage.

Other studies have linked green tea consumption to digestive health, showing improved growth of good gut bacteria in both the intestines and the mouth.

Green tea also shows promise in relation to Parkinson’s disease. This progressive neurological condition affects around 1 in every 350 adults in the UK and results from the loss of dopamine producing brain cells. Following previous research suggesting a neuroprotective effect of green tea, more recent research based on an animal model discovered that the polyphenols in green tea may protect dopamine neurons and that the effect increases with the amount consumed.

Finally, combined results from a human supplementation trial and a laboratory study suggest that drinking green tea every day may even protect against damage at a genetic level. The study, published in the British Journal of Nutrition found that four weeks of drinking green tea reduced DNA damage by 20%.

 

Chill out!

With more and more people suffering from anxiety disorders and stress, another great reason for drinking green tea is for its theanine content. Theanine is a naturally occurring amino acid that is able to cross the blood-brain barrier where it has been found to promote alpha brain waves, producing a calming and focused effect, which helps us to relax from the stresses of daily life without causing drowsiness. Theanine is thought to increase levels of GABA, the neurotransmitter responsible for feeling calm and chilled.  What’s more, combining theanine with the naturally occurring caffeine in green tea has been found to be particularly effective in improving brain function.

So green tea provides the best of both worlds! Generally providing roughly a third of the amount of caffeine of a typical cup of coffee, it can help to improve calm and focus without the jitteriness that may be associated with other more highly caffeinated drinks.  Another good reason to relax with a warming cup of the green stuff!

 

 

References:

- Kuriyama S et al (2006). Green tea consumption and mortality due to cardiovascular disease, cancer, and all-cause mortality. JAMA 296: 1255-65

Samavat S et al (2016). Effects of green tea catechin extract on serum lipids in postmenopausal women: a randomized, placebo-controlled clinical trial. American Journal of Clinical Nutrition; 104 (6) 1671-1682

Dulloo A 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, The American Journal of Clinical Nutrition, 70 (6): 1040–1045

2005 Body weight loss and weight maintenance in relation to habitual caffeine intake and green tea supplementation. Obes Res. 13(7):1195-204.

Guo et al. Protective Effects of Green Tea Polyphenols in the 6-OHDA Rat Model of Parkinson’s Disease Through Inhibition of ROS-NO Pathway. Biological Psychiatry 62 (12) 1353 - 1362

Han KC et al (2010). Genoprotective effects of green tea (Camellia sinensis) in human subjects: results of a controlled supplementation trial. Br J Nutr.

2008 L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. 17 (1)167-8.

2008. L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. J Nutr. 138(8):1572S-1577S.

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