Green tea

Tea for two and two for tea... Would you like a cup of tea? Tea yes, but green tea please, because unlike the beverage so popular with the British, which is certainly good for your health but often consumed for the pleasure of your taste buds, green tea offers health benefits that go far beyond a simple relaxing break!

Green Tea Leaf Overview

Green tea and its leaf come, as their name indicates, from the tea plant, a shrub of the Theaceae family native to the Far East. Its scientific name “camellia sinensis” literally means “Chinese camellia”. The tea plant is mainly grown in China and Japan as well as in India, but it is still possible to find green tea from Kenya, Sri Lanka, Vietnam and Turkey.

The green tea leaves that we usually consume as a beverage come from the natural oxidation of the leaves after picking. These small leaves are picked directly from the bush, withered and then rolled using a process of extracting the juices and finally heated and dried.

Green tea is unoxidized because the natural oxidation process of the leaves is stopped very quickly after picking. It is the action of heat, which neutralizes the enzyme at the origin of this oxidation, which makes it possible to obtain green tea.

Unusual : the oldest tea plant in the world is said to be hidden in China, in the hollow of the Yunnan mountains, and is said to be around 3200 years old. Very far from the shrub known to all, this camelia sinensis is said to measure around 10m in height with a circumference of 5 to 6m.

Composition and medicinal properties of green tea leaf

The green tea leaf is composed of a complex mixture of more than 500 active substances of interest for health.

Please note: the nature of the tea, the infusion time, the nature (more or less calcareous) and the temperature of the water, have a huge influence on the composition of the drink.

Theanine is one of the main compounds of the green tea leaf. It is an amino acid that acts on the brain in two different ways mainly. On the one hand, theanine will have a relaxing effect on the central nervous system , and thus participate in the reduction of mental and physical stress; on the other hand and this simultaneously, it will produce a stimulating effect on the immune system , thus strengthening the body's ability to defend itself.

Green tea also contains a good number of polyphenols. Polyphenols are powerful antioxidants. Depending on the variety of tea and the manufacturing process used, the nature of the polyphenols present in green tea may vary slightly.

However, the green tea leaf mainly contains catechins that will be transformed into theaflavins and thearubigins by the fermentation process of the leaves. These antioxidant compounds with very powerful properties help to protect the body against free radicals that cause cell aging, but will also stimulate cognitive functions, such as memory for example, as well as increase the production of the alpha rhythm in the brain (a rhythm significant for a state of relaxation).

The polyphenols present in green tea make it an interesting drink for the prevention of certain cancers, as well as for protecting the cardiovascular system and in particular reducing the level of bad cholesterol in the blood.

The various components of the tea leaf are also said to have a stimulating effect on the metabolism. This action would limit the absorption and assimilation of lipids by the stomach and intestine, increase the basic metabolism and thermogenesis and have a diuretic effect. These various combined benefits make green tea a drink particularly suitable to accompany a slimming diet.

Green tea also contains many vitamins. Among them, we can mention the particularly high presence of vitamin C, with between 150 and 300 mg per 100 g of leaves.

Green tea leaves also contain significant levels of B vitamins, vitamin E and vitamin K. It also contains minerals such as fluoride, manganese and nickel.

Green tea, long studied by the scientific community

Traditionally used for its multiple health benefits, the green tea leaf has been the subject of much scientific research.

For example, Japanese researchers studied the effects of green tea on the cardiovascular health of several groups of individuals. After 6 weeks of daily consumption of green tea, they were able to observe a decrease in total cholesterol of 6.7%, reaching minus 11.3% on average after 12 weeks of supplementation (1).

Another study, this time American, demonstrated that the polyphenols present in green tea had a beneficial effect on the prevention of cancers (2). Many studies exist dealing with the same subject and confirming the age-old use of green tea as a health asset.

In 2010, a meta-analysis of several scientific studies on the effects of green tea on weight loss showed that the catechins and caffeine present in tea leaves could facilitate weight loss. In fact, individuals who supplemented daily with green tea extracts rich in catechins (580 to 710 mg) and caffeine (40 to 110 mg) in addition to their diet saw their Body Mass Index decrease. It is the combination of the two substances present in green tea that would be at the origin of the slimming effects (3).

Other studies have confirmed that green tea helps increase the body's energy expenditure while accelerating the breakdown and elimination of stored fat in the body , thus promoting weight loss. (4) (5)

Finally, among the multitude of studies conducted on the various effects of green tea, let us mention research concerning its stimulating action on the brain , with positive effects on memory and neural connections. In 2014, a study showed that consuming a green tea extract at a rate of 27.5 g would improve memory and the formation of neural connections. (6)

Use and dosage of green tea

In capsule or extract form, it is customary to consume between 1200 and 2300 mg of green tea per day.

Taken as an infusion, at a rate of 3 to 10 cups per day, the diuretic and detoxifying effects of green tea will obviously be increased.

Contraindications and precautions for the use of green tea

It can be said that daily consumption of green tea is generally safe for health. However, it is important to know that, in the case of multiple supplementation, green tea could reduce the absorption of iron or folic acid, and could have interactions with certain antidepressant medications.

In people with diabetes, green tea may have an influence on blood sugar levels.

Finally, excessive consumption could be a source of insomnia or nervousness in some people.

A tea time with multiple virtues

It seems entirely appropriate and safe to consume green tea, especially when you want to support a weight loss process, or as part of an overall healthy diet, to strengthen different functions of the body.

1. Green Tea Consumption and Mortality Due to Cardiovascular Disease, Cancer, and All Causes in Japan , S Kuriyama, T Shimazu, K Ohmori, N Kikuchi, N Nakaya, Y Nishino, Y Tsubono, I Tsuji, JAMA. 2006;296:1255-1265.
2. Boehm K, Borrelli F, Ernst E, Habacher G, Hung SK, Milazzo S, Horneber M, Green tea (Camellia sinensis) for the prevention of cancer , Cochrane Database of Systematic Reviews, 2009, Issue 3. Art. No.: CD005004. DOI: 10.1002/14651858.CD005004.pub2
3. Phung OJ, Baker WL, et al. Effect of green tea catechins with or without caffeine on anthropometric measures: a systematic review and meta-analysis . Am J Clin Nutr. 2010 Jan;91(1):73-81. Epub 2009 Nov 11. Review.
4. Nagao T, Hase T, Tokimitsu I. A green tea extract high in catechins reduces body fat and cardiovascular risks in humans . Obesity (Silver Spring). 2007 Jun;15(6):1473-83.
5. Dulloo AG, Duret C, et al. 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. 1999 Dec;70(6):1040-5.
6. Schmidt A et al Green tea extract enhances parieto-frontal connectivity during working memory processing. Psychopharmacology (Berl). 2014 Oct;231(19):3879-88