Insight and Approaches on the Health Benefits of Green Tea

By Sandra Nomoto

Quality of Tea Guarantees its Place in Pharmacy

Camellia sinensis, commonly known as green tea, represents about 20 percent of the dried tea that’s manufactured and consumed annually, mainly in Asian countries.

Green tea possesses different classes of chemical compounds: polyphenols, alkaloids, proteins, minerals, vitamins, and amino acids. Its positive health properties are anticancer, anti-oxidant, anti-hypercholesterolemic, and antimicrobial, in addition to its effectiveness in reducing body weight. This article explores some of these applications, based on scientific studies.

Antioxidant and Hepatoprotective Effects

Traditional medicine considers green tea to have antioxidant potency. Its polyphenolic compounds possess different degrees of free radical scavenging properties.

Green tea polyphenols (GTPs) increase excretion of carcinogenic products in the body. It inhibits oxidative DNA damage and cell proliferation in the liver, hepatotoxicity, and counterattacks free radicals produced during metabolism of xenobiotics in the liver. A dietary green tea extract treatment reduces liver injury. In addition, it has a therapeutic effect against alcohol-induced damage.

Anticancer Effects

The polyphenols and epi-gallo catechin gallate (EGCG) in green tea have a significant anticarcinogenic effect against different types of cancer. Oral or topical application of GTPs antagonizes skin tumours, inhibits the formation of UVB light-produced skin lesions, protects against UVB-induced immune suppression and skin cancer, reduces UVB-induced skin redness, and causes significantly fewer UVA+B light-induced skin papillomas.

Many studies reported that green tea could be used in the treatment of malignant melanoma. In lung cancer, EGCG infusion revealed effectiveness in alleviating lung cancer, and inhibited lung cancer stem cells.

Daily consumption of green tea catechins ameliorated breast cancer. It could reduce the average sizes of tumours and mortality from induced mammary carcinogenesis. Polyphenon E exerted a mild inhibitory effect on early stage breast cancer, and catechins could act in the post-initiation stage.

Green tea proved to be effective against human prostate cancer cells. Catechins can prevent inflammatory processes associated with glioma tumour growth, and serve as a chemopreventive agent.

Antimicrobial and Antiviral Effects

Many studies reported the antimicrobial activity of green tea. It was effective against Staphylococcus epidermidis, Staphylococcus aureus, and Vibrio cholerae O1. Raw extract of green tea, especially gallocatechin gallate (GCG), suppressed 1-deoxy-d-xylulose 5-phosphate reductoisomerase activity, which is an antimicrobial target. It may also reduce the lethality of ricin toxin.

In the case of Bacillus stearothermophilus and Clostridium thermoaceticum, tea polyphenols have the ability to inhibit the development and growth of bacterial spores due to their ability to decrease the heat resistance of these spores when added at high temperature.

Tea exhibits antiviral activity and serves as a chemopreventive agent. Its contained flavonoids stimulate Natural killer (NK) cell activity, so it may be used in the treatment and prevention of viral diseases. Recently, it was found that EGCG was capable of inhibiting the Brazilian strain of Zika virus. Topical application of EGCG can also be used to prevent the sexual transmission of HIV.

Cardioprotective Effects

Green tea could improve the risk factors for heart disease. It reduces total cholesterol, low density lipoprotein (LDL) cholesterol, and blood pressure. Non fermented Chinese green tea lowers the risk of coronary heart diseases, and has protective effects against cardiovascular diseases.

Green tea consumption decreases the risk of myocardial infarction (MI). High dietary intake of green tea may be useful in the reduction and prevention of cardiac injury following ischemia.

Photo: Sergei Norkov

The flavonoids in green tea are responsible for its cardio-protective effect. EGCG reduces cardiotoxicity and inflammation, and preserves heart function.

Fresh green tea fermented under nitrogen gas was proved to prevent the occurrence of hypertension, and both theanine and decaffeinated green tea extract exerted a decline in blood pressure. Green tea extract prevented hypertension and accompanied organ damage.

Antidiabetic and Anti-Obesity Effects

Green tea is used to treat diabetes and its complications, specifically diabetes mellitus. EGCG controls hyperglycemia and alleviates diabetes complications by reducing plasma glucose, insulin level, and liver and kidney weight.

GTPs increase glucose tolerance and reduce elevated serum glucose levels. Floratheasaponins A, B, and C in the flower buds of green tea exhibit inhibitory effects against serum glucose elevation.

Green tea extract is a well-tolerated natural product for managing obesity. It reduces fat digestion and stimulates energy expenditure and fat oxidation through EGCG and caffeine, without significant differences in plasma cholesterol or blood pressure.

Recent studies confirmed that a mixture of green tea catechins and caffeine had a beneficial effect on body-weight management.

Neuroprotective Effects

Green tea extract has a protective effect on ischemia/reperfusion-induced brain injury and behaviour deficit. EGCG has a protective effect against stress-induced neural injuries, is easily absorbed from the digestive tract, and penetrates the brain. I-theanine reduces brain cadmium levels and oxidative damage, which leads to neurodegenerative diseases.

GTPs serve as neuroprotective, therapeutic agents to alter brain aging processes in major neurodegenerative disorders such as Parkinson’s disease and Alzheimer’s disease. Both tea and EGCG, when used alone or with Parkinson’s disease’s inducers, provide a neuroprotective effect. Green tea catechins possess an inhibitory effect against β-secretase, one of the most important enzymes in Alzheimer’s disease.

The theanine in green tea enhances memory and learning ability. Polyphenols also have a potential role in the treatment of dementia. Drinking theanine-rich and low-caffeine green tea has anti-stress effects, and theanine encourages relaxation.

Anti-Inflammatory and Anti-Allergic Activity

Green tea is considered a potent anti-inflammatory and antipyretic agent. It exerts suppressive activities against the activation of human polymorphonuclear neutrophils (PMNs) associated with inflammatory reactions. Green tea extract/tablets were effective in controlling pain particularly in osteoarthritic patients.

Green tea has an anti-allergic effect due to leaf saponins and floratheasaponins from flower buds that possess anti-allergic activities. Methylated EGCG blocks the production of two compounds in the body involved in producing allergic responses, and works by triggering and sustaining allergic reactions.

Current Trends in Green Tea

More research on other tea varieties is needed to develop advanced, high-quality products to meet consumer demand and find out other active constituents for pharmaceutical applications.

Many tea products should be carefully considered. For instance, kombucha tea—a type of sugared tea obtained by fermentation primarily by acetic acid bacteria and yeast (tea fungus)—is known worldwide, owing to its massive beneficial and refreshing potentials. Special consideration should be given to kombucha, which was found to be effective in the prohibition of many types of cancer, alleviation of cardiovascular disorders, enhancement of liver functions, and probing of the immune system.

The information in this article was taken from the study results published in Antioxidants by Maram M. Aboulwafa, Fadia S. Youssef, Haidy A. Gad, Ahmed E. Altyar, Mohamed M. Al-Azizi, and Mohamed L. Ashour.

This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. We advise readers to always seek the advice of a physician or other qualified health provider with any questions you may have regarding a medical condition.

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