Our assets 07/12/2020
Spotlight on a magical elixir: Green Tea
Before being the second most consumed beverage in the world after water, green tea is first and foremost a medicinal plant favoured by traditional Asian medicine. Crowned with numerous virtues, green tea is renowned for its benefits on the body and mind. Its leaf contains more than 400 constituents with tonic, diuretic, digestive, depurative, cardioprotective and anti-inflammatory powers. But what makes green tea unique are its catechins, polyphenols that give it the greatest antioxidant capacity of all foods. Focus on a stimulating, invigorating and soothing elixir.
Properties and benefits of green tea
Of all the teas (black, white, red, smoked, etc.), green tea is the one most renowned for its health benefits. It is the variety that has undergone the least processing: it is not fermented, its leaves are simply dried and not oxidised, unlike black tea. Its antioxidant powers are therefore superior to other teas.
The virtues of green tea are mainly concentrated in its polyphenols, and more particularly in its catechins. Present in large quantities, these powerful antioxidants have the capacity to oppose free radicals, thus preserving the immune system. Rich in tannins, flavonoids, theanine, caffeine and gallic acid, green tea also contains vitamins, amino acids, minerals, trace elements and essential oils.
Catechins
Most of the research on the benefits of green tea focuses on catechins, and in particular on epigallocatechin-3-gallate (EGCG). Green tea contains 4 catechins: epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG).EGCG has been in the spotlight since the 1980s and is described as the 'miracle molecule' of green tea. This polyphenol, which makes up 50-75% of the catechins in green tea, is a powerful antioxidant. Clinical tests have shown that EGCG prevents the formation of free radicals and helps regulate oxidative stress induced by external (UV rays, tobacco, etc.) and internal (degenerative diseases, diabetes, tumours, etc.) aggressions.
Scientists have also shown that EGCG inhibits the synthesis of an enzyme involved in the production of a hormone called cortisol. Cortisol plays a key role in the regulation of many physiological processes such as blood pressure, cardiovascular function, carbohydrate metabolism and immunity. Prolonged cortisol secretion can therefore lead to various disorders such as type 2 diabetes, hypertension, obesity and reduced immune defences.
Theanine or L-theanine
Theanine is an amino acid that acts on the brain and is found only in tea. It induces a reduction in mental and physical stress and has a relaxing effect. Theanine is said to increase the concentration of serotonin and dopamine, the famous "happiness hormones".
Caffeine
The caffeine in tea, also called theine, has an effect on physical and mental energy. Unlike coffee caffeine, green tea caffeine is bound to its tannins, which makes it more tolerable. The process of penetration of green tea caffeine into the bloodstream is indeed smoother and more gradual and its benefits last longer. Thus, it gently tones the nervous system, in a prolonged and more relevant way.
Green tea under the scientific microscope
The richness of the components of green tea has fascinated researchers for decades. The first clinical research began in Japan in the 1970s. Since then, thousands of studies have been carried out in the United States, China and Europe, highlighting the numerous benefits of green tea for the body.
Antioxidant properties
The powerful antioxidant effect of green tea comes mainly from its high concentration of polyphenols and catechins. These capture and help to eliminate free radicals that are harmful to the body and the proper functioning of the metabolism.
Anti-inflammatory properties
Green tea owes its anti-inflammatory properties to its high content of polyphenols, especially EGCG. This catechin has an antioxidant power approximately 200 times greater than that of vitamin E. Studies have shown that this molecule may have a strong potential to treat rheumatoid arthritis thanks to its ability to block the TAK1 protein, which plays a key role in inflammation.
Cardiovascular protection
The cardioprotective effect of green tea is thought to be linked to its high concentration of EGCG. This catechin stimulates cardiac activity, softens the walls of the blood vessels and limits the formation of fatty plaques that can lead to the obstruction of arteries. Green tea therefore has positive effects on arteriosclerosis, stroke, myocardial infarction and other cardiovascular diseases.
Glycemic balance
A meta-analysis published in 2013 shows that the EGCG in green tea reduces the risk of insulin resistance, thus helping people with type 2 diabetes. The effects of polyphenols on glucose metabolism are explained by a decrease in intestinal glucose absorption, improved sensitivity of pancreatic glucose receptors, and better absorption of glucose by peripheral tissues.
Cholesterol
The flavonoids in green tea prevent the intestine from absorbing bad cholesterol. Studies show that regular consumption of green tea lowers bad cholesterol levels and increases good cholesterol.
Brain, memory, concentration
Several scientific studies have shown the protective role of green tea catechins in the onset of dementia and neurodegenerative diseases, such asAlzheimer's and Parkinson's. Its high concentration in polyphenols, and particularly in EGCG, would contribute to stop the formation of certain proteins responsible for cognitive decline.
In addition to its neuroprotective effects, researchers have identified two compounds in green tea that may reduce mental fatigue and increase attention. Caffeine - a powerful stimulant for the brain - and L-theanine. The combination of these two molecules would improve brain function.
Weight management
Very popular when trying to control weight, drinking green tea is said to increase energy expenditure. Its active ingredient, EGCG, is said to reduce the absorption of fats in the intestine, limit the production of adipocytes where body fat accumulates, increase fat oxidation and inhibit fat production. In addition, by regulating blood sugar levels and limiting insulin sensitivity, it promotes the elimination of excess fat.
Depressive disorders
Several studies have highlighted the benefits of green tea on mood. According to a Chinese study, regular consumption of green tea reduces the prevalence of depressive symptoms. Although the researchers do not know the exact reasons for these benefits, they explain that green tea stimulates the nervous circuits linked to pleasure. The researchers suppose that the polyphenols contained in green tea act on dendritogenesis, i.e. the way in which neurons connect to each other.
Anti-stress
Although it contains some caffeine, green tea is deeply relaxing and soothes nervous tension. Its leaves contain L-theanine, an amino acid that induces the production of relaxing alpha waves in the brain. It is also said to help peoplefall asleep.
Skin protection
Because it is highly concentrated in polyphenols, green tea has a positive impact on skin cells. Its catechins, and particularly EGCG, neutralise the free radicals responsible for premature skin ageing. Its molecules boost collagen production and help preserve the skin's elasticity.
Anti-cancer properties
At the heart of scientific research, green tea is considered a valuable ally in the fight against cancer. Researchers have shown the promising role of catechins, powerful antioxidants belonging to the flavanols. All four types of catechins play an important role, but the most powerful is EGCG. This molecule is said to have the property of "asphyxiating tumours". Indeed, when cancer cells proliferate to form a small tumour, they need to build up a network of blood vessels in parallel in order to be fed and be able to multiply. This is known as the process of angiogenesis. EGCG is said to have the property of preventing angiogenesis, the formation of the blood network necessary for any tumour to form and grow.
How to consume green tea?
Green tea is consumed as a hot or cold drink (infusion of the leaves) or as a food supplement. It is used in cooking recipes for its pretty colour and subtle taste, particularly in cakes, muffins, cupcakes, ice cream and milkshakes. Cosmetics have also adopted this virtuous plant for the design of anti-ageing treatments.
Sources
Beneficial Properties of Green Tea Catechins, International Journal of Molecular, Claudia Musial, Alicja Kuban-Jankowska, Magdalena Gorska, Sciences 21(5):1744, March 2020.
Green Tea and One of Its Constituents, Epigallocatechine-3-gallate, Are Potent Inhibitors of Human 11β-hydroxysteroid Dehydrogenase Type 1, Jan Hintzpeter. Claudia Stapelfeld, Christine Loerz, Hans-Joerg Martin, Plos One, January 2014.
L-Theanine reduces psychological and physiological stress responses, Kenta Kimura, Makoto Ozeki, Lekh Raj Juneja, Hideki Ohira, Biological Psychology, p-39-45, January 2007.
Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses, Ai Yoto, Mao Motoki, Sato Murao, Hidehiko Yokogoshi, Journal of Physiological Anthropology, 2012.
Antioxidant mechanism of tea polyphenols and its impact on health benefits, Zhaomong Yan, Yinzhao Zhong, Yehui Duan, Animal Nutrition, January 2020.
Anti-inflammatory Action of Green Tea, Tomokazu Ohishi a, Shingo Gotob, Pervin Monirac, Mamoru Isemura b,c, Yoriyuki Nakamurac, Anti-Inflammatory & Anti-Allergy Agents in Medicinal Chemistry, September 2016.
The Impact of Green Tea and Coffee Consumption on the Reduced Risk of Stroke Incidence in Japanese Population, Yoshihiro, Hiroyasu Iso, Isao Saito et al, The Japan Public Health Center-Based Study Cohort, 2013.
Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials, Kai Liu, Rui Zhou, Bin Wang, Ka Chen et al, The American Journal of Clinical Nutrition, August 2013.
Systematic review of green tea epigallocatechin gallate in reducing low-density lipoprotein cholesterol levels of humans, Yuko Momose, Mari Maeda-Yamamoto, Horoshi Nabetani, International Journal of Food Sciences and Nutrition, June 2016.
Neurological mechanisms of green tea polyphenols in Alzheimer's and Parkinson's diseases, Orly Weinreb, Silvia A Mandel, Tamar Amit, Moussa B Youdim, Journal of Nutritional Biochemistry, October 2004
L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance, Simon P. Kelly, Manuel Gomez-Ramirez, Jennifer L. Montesi, John J. Foxe, The Journal of Nutrition, August 2008
A Brief Review on Green Tea and its Effect on Weight Management, Abhinav Joseph et al, Journal of The Guajarat Research Society, 2019.
Effect of green tea on reward learning in healthy individuals: a randomized, double-blind, placebo-controlled pilot study, Qiangye Zhang, Hongchao Yang, Jian Wang et al, Nutrition Journal, June 2013.
Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content, Keiko Unno, Shigenori Noda, Yohei Kaeasaki et al, Nutrients, July 2017.
Protective Mechanisms of Green Tea Polyphenols in Skin, Patricia Oyetakin White, Heather Tribout, Elma D Baron, Oxidative Medicine and Cellular Longevity, June 2012.
Cancer Prevention with Green Tea and Its Principal Constituent, EGCG: from Early Investigations to Current Focus on Human Cancer Stem Cells, Hirota Fujiki, Tatsuro Watanabe, Eisaburo Sueoka et al, Molecules and cells, February 2018.
