Health Benefits of Green Tea

This article is intended to provide a general overview of the potential health benefits of green tea and should not be interpreted as a substitute for professional medical advice or treatment. If you have any specific health concerns or questions, please consult with a qualified healthcare provider.

The information in this article is derived from various sources, including the internet, popular science magazines, and scientific studies. It is essential to note that scientific research is ongoing, and new findings may emerge that could impact the conclusions or recommendations presented in this article.

Tea beverages are becoming increasingly popular among consumers due to their health and convenience benefits. This paper briefly introduces the main components of tea leaves and discusses the functional properties of tea polyphenols, which have antioxidant, antimutagenic, and cardiovascular disease-relieving effects, among others. The future development prospects of tea polyphenols are also discussed.

Tea beverages are liquid products made from tea leaf water extracts or concentrated tea powder as the main raw material, which are processed through filtration, blending, sterilization, and filling, and contain a certain amount of effective tea ingredients and the flavor of tea (Sun Qifu et al., 2003). According to the formula of tea beverages, they can be divided into pure tea beverages, flavored tea beverages, and functional tea beverages. Tea beverages have the characteristics of being natural, healthy, thirst-quenching, and refreshing. They are more refreshing and thirst-quenching than carbonated beverages and more palatable than water beverages. They are light and fragrant, rich in health-care ingredients, and have nutritional and health-care functions. In recent years, the variety of tea beverages has been continuously developing. In the 1970s, black tea beverages appeared, in the 1980s, oolong tea was the main ingredient, and with the improvement of technology, green tea beverages gradually became the leading product.

Green Tea

Tea is one of the three major beverages in the world. Recently, beverages based on green tea as a raw material have become increasingly popular. Since the International Tea and Health Symposium in 1991, it has been confirmed and verified by various methods that tea is beneficial to health and has the effect of preventing and treating diseases, and the beneficial substances and mechanisms of action of green tea have been discovered.

1. Main Components of Green Tea

The various chemical components contained in green tea are essential nutrients for the human body or have important health care value. The chemical components present in tea leaves include tea polyphenols, caffeine, lipopolysaccharides, carbohydrates, proteins, enzymes, vitamins, and minerals.

Tea polyphenols are a collective term for polyphenol compounds, which are the main effective components in tea leaves. They are also known as tea tannins or tea tanning agents and consist of more than 30 polyphenol substances. Tea polyphenols account for 20% to 35% of the dry weight of young tea shoots. They mainly include catechols, flavones, anthocyanins, and phenolic acids. Among them, catechols have the highest content. Many of the important effects of tea are related to tea polyphenols, such as various health-care functions, including antioxidant, anti-tumor, anti-atherosclerosis, blood sugar-lowering, anti-caries, tooth protection, and antibacterial effects.

Tea Polyphenols

Caffeine, also known as theine, accounts for 2% to 5% of tea leaves, with small amounts of theophylline and theobromine, all of which are soluble in hot water. Caffeine can stimulate the central nervous system, enhance the excitation process of the cerebral cortex, and thus achieve the purpose of invigorating the spirit and improving work efficiency. Caffeine is a vasodilator that can accelerate breathing and increase muscle workload without increasing pulse rate or blood pressure. It works synergistically with tea polyphenols to prevent an increase in cholesterol in the human body and has the effect of preventing myocardial infarction.

Lipopolysaccharides generally account for 3% of tea leaves. Pharmacological experiments have shown that when appropriate plant lipopolysaccharides enter the body, they can enhance the body's non-specific immunity in a short period of time, which has a great effect on improving the body's resistance to diseases.

Vitamins are present in more than 10 varieties in tea leaves, such as vitamins C, E, and D. Among them, the content of vitamin C is richer than that of other plants, being 2 to 3 times more than lemon juice and orange juice.

2. Health Benefits of Green Tea

2.1 Antimutagenic and Anticancer Effects

Free radicals are active chemical substances with a lively nature and extremely strong oxidizing capacity. They can induce the oxidation of unsaturated fatty acids in the body, producing lipid peroxides. During normal life activities, the body continuously produces harmful free radicals due to metabolism. Their production and accumulation can restrict and destroy the normal function of biological membranes, affect the normal metabolism of active substances, and trigger many diseases such as hepatitis, cancer, and cardiovascular diseases.

Tea polyphenols in green tea are a class of chemical substances containing polyphenol hydroxyls that are easily oxidized to esters and thus provide protons (H+). Therefore, they have remarkable antioxidant characteristics. The antioxidant capacity of tea polyphenols is 18 times that of vitamin E and 3 to 10 times that of vitamin C. Numerous medical experiments have proven that the strong antioxidant capacity of tea polyphenols can eliminate free radicals in the body, inhibit the activity of lipoxygenase and lipid peroxidation, block the synthesis of N-nitroso compounds, inhibit the covalent binding of carcinogens to cellular DNA, and prevent single-strand breaks in DNA. It can also induce an increase in the activity of metabolic enzymes in the human body, promote the detoxification of carcinogens, prevent cancer and gene mutations, and enhance the immune function of body cells.

According to the journal Cancer Research, green tea polyphenols help prevent the spread of prostate cancer by attacking molecular pathways that fuel tumor cell growth and spread and by inhibiting the growth of blood vessels that feed tumors. Researchers at the University of Wisconsin and Case Western Reserve University demonstrated that green tea polyphenols (GTP) can modulate the insulin-like growth factor-1 (IGF-1)-driven molecular pathways in a mouse model of human prostate cancer. Studies have shown that increased IGF-1 levels are associated with an increased risk of some cancers, including prostate, breast, lung, and colon cancers. GTP can reduce IGF-1 levels and increase the levels of one of IGF-1's binding proteins, insulin-like growth factor binding protein-3. GTP can also reduce the expression of proteins associated with cancer cell metastasis and spread, inhibiting the levels of urokinase plasminogen activator and matrix metallopeptidases-2 and -9.

Brewing Green Tea

Numerous studies have reported that tea has anti-cancer and cancer-preventive effects in animal models, including tissues and organs such as the oral cavity, skin, lungs, esophagus, large intestine, pancreas, bladder, prostate, and mammary glands. The Institute of Tumor Research of the Chinese Academy of Medical Sciences conducted an anti-cancer screening of 108 foods, and the results showed that green tea extract had the best effect. A case-control study conducted by a scholar in Shanghai showed that regular consumption of green tea reduced the risk of esophageal cancer, especially in people who did not smoke or drink alcohol. Other reports have shown an inverse correlation between green tea consumption and the risk of pancreatic cancer in humans. In an animal experiment with rats, the intake of green tea extract significantly alleviated the acute liver damage caused by D-galactosamine to the liver of rats. A study reported that subjects who drank 3 cups of green tea per day for 6 months significantly reduced the frequency of sister chromatid exchanges in peripheral blood lymphocytes in the smoking population. One of the most important advantages of green tea as a cancer preventive agent is its low toxicity. Not all green tea catechins have the same activity. For example, epigallocatechin gallate (EGCG) is more active than non-gallated catechins because of its lower redox potential. Although studies have shown that some catechins, such as epicatechin (EC), have synergistic effects with other catechins and caffeine, their effects on specific cancer cell lines are weaker. Therefore, a complex green tea extract is more potent than a single component.

2.2 Prevention and Treatment of Hyperlipidemia-Induced Disease

Tea polyphenols' antithrombotic, profibrinolytic, and anti-platelet aggregation effects, as well as their ability to lower blood pressure, reduce lipids, lower blood sugar, and prevent arteriosclerotic, are all due to their strong ability to donate electrons. They easily combine with enzyme proteins and can form a complex with thrombokinase, preventing fibrinogen from being converted into fibrin. Simultaneously, tea polyphenols, by oxidizing themselves, can inhibit the oxidation of cholesterol and unsaturated fatty acids, which not only reduces the deposition of cholesterol and its oxides on arteries but also promotes the transport and elimination of unsaturated fatty acids on cholesterol. Tea polyphenols can also significantly reduce aggregation and lower the permeability of endothelial cells by the masking effect on the surface of the arteries, thereby preventing thrombosis.

The effect of tea polyphenols on serum cholesterol is mainly manifested through the elimination of cholesterol accumulation on the walls of the blood vessels by increasing the content of high-density proteins (HDL-C) and simultaneously inhibiting the cellular of low-density proteins (LDL-C), thereby reducing blood lipids and preventing and alleviating arteriosclerotic.

2.3 Hypotensive and Hypoglycemic Effects

One of the functions of human kidneys is to produce "angiotensin" that increases blood pressure and "bradykinin" that lowers blood pressure, thereby maintaining blood pressure equilibrium. When the activity of the enzyme that assists the conversion of these two substances is too strong, angiotensin increases, and blood pressure rises. Tea polyphenols have a strong effect on inhibiting the activity of conversion enzymes. Therefore, it can lower blood pressure or maintain blood pressure stability.

Diabetes is caused by a lack of insulin and an excess of blood sugar, resulting in disordered metabolism of sugar, fat, and proteins. Tea polyphenols and polysaccharide have a stimulating function on insulin synthesis. Tea polyphenols play a regulatory role in the body's sugar metabolism. They can lower blood sugar levels, effectively preventing and treating diabetes. Experimental data confirm that tea polyphenols are an amylomaltaase enzyme, so they can inhibit the conversion of sugar into glucose, causing blood sugar to drop.

2.4 Effects on Apoplexy Prevention

One of the causes of apoplexy is excessive peroxidation in the human body, which causes loss of vascular wall. Tea polyphenols inhibit the production of peroxidation, maintain the vascular wall's flexibility, relax the vascular wall, relieve vascular spasm, increase the effective diameter of blood vessels, and lower blood pressure through vascular expansion, thereby effectively preventing apoplexy.

2.5 Antithrombotic Effects

The increase of fibrinogen in plasma can cause the aggregation of red blood cells, leading to increased blood density. This promotes the formation of thrombosis. Additionally, the increase of phospholipids and cholesterol in the membrane lipids of cells reduces the deformability of red blood cells and seriously affects the perfusion of microcirculation. It increases blood density, causing blood stasis in capillaries and aggravating aggregation of red blood cells and thrombosis. Tea polyphenols protect and restore the deformability of red blood cells. They easily form complexation with the clotting enzyme, preventing the conversion of fibrinogen into fibrin. Also, tea polyphenols can effectively inhibit the increases of cholesterol content in plasma and among hepatic and help them to expel lipids and cholecystokinin from the body, effectually preventing the formation of thrombosis.

2.6 Enhancement of General Immune Capacity

By increasing the total activity of immunoglobulin, the immune capacity of the entire person is elevated, achieving effects such as increasing the total amount of immunoglobulin in the human body, maintaining it at a high level, stimulating the variation of antibody activity, thus improving the immune capacity of the whole body, and promoting the auto-conditioning function of the body.

Tea polyphenols can inhibit and kill the bacterial infections of Streptococcus, Corynebacterium, Salmonella, Pneumococci, Cholera bacillus, and Staphylococci. They can reduce the toxicity of diphtheria toxin and tetanus toxin, or they can have anti-herpes virus, mumps virus, measles virus, vaccinia virus, and acquired immune deficiency virus on the human body, and they can inhibit the invasion of the human body by Treponema pallidum and Candida albicans, and they can resist various anti-rheumatic factors.

2.7 Relieving Intestinal Tension, Preventing Inflammation and Diarrhea, and Diuretic Effects

Constipation is a common disease among middle-aged and elderly people, mainly caused by the slow contraction of intestinal muscles and long-term mental stress. Tea polyphenols have the effect of stimulating gastrointestinal reactions and accelerating colon peristalsis to treat constipation. Catechins can inhibit H-K-ATPase on the gastric mucosa, thereby fundamentally inhibiting the secretion of gastric acid, reducing the stimulation and damage of gastric acid to the gastric mucosa. At the same time, catechins can also treat ulcers. In addition, catechins also have a certain effect on relieving gastrointestinal spasms. Tea polyphenols are also effective in treating constipation, controlling intestinal flora, improving, and regulating the intestinal environment. Tea polyphenols inhibit and kill various harmful pathogenic bacteria that cause diarrhea by enhancing the body's comprehensive immune capacity. They also relax the stomach and intestines to achieve the effect of anti-inflammatory and antidiarrheal. The flavonol compounds in tea polyphenols can stimulate renal vasodilation, increase renal blood flow, thereby increasing the glomerular filtration rate, allowing the lactic acid in urine to be excreted. Lactic acid in human muscles and tissues is a fatigue substance, and the excretion of lactic acid from the body can allow the fatigued body to recover.

2.8 Neuroprotective Effects

To date, in vitro evidence for the neuroprotective effects of green tea polyphenols has been obtained in cultured cells with certain neuronal characteristics.

6-hydroxydopamine (6-OHDA) is commonly used as a neurotoxin to study the mechanisms of neuronal damage. In cultured PC12 cells, the primary component of GTP, EGCG (epigallocatechin gallate), 200 mmol/L, can significantly inhibit 6-OHDA-induced apoptosis. Different components of GTP have different effects on 6-OHDA-induced apoptosis of PC12 cells. EGCG is a potent iron chelator, which can partly explain its neuroprotective effects. Many studies suggest that iron accumulation is associated with a series of neurodegenerative diseases, and iron also accumulates in the substantia nigra neurons of Parkinson's disease patients.

At the 14th International Parkinson's Disease Congress held in 2001, Israeli scientists announced that they had studied green tea extract polyphenol EGCG using gene chip technology and found that it has a strong neuroprotective effect on Parkinson's disease. In rodent models of drug-induced Parkinson's disease, the expression levels of 51 genes were found to have changed. These genes include NFxB and IL, B genes. In some cases, they can even be increased by more than 10 times. However, giving animals oral EGCG for 2 days before giving the same inducing drug will prevent changes in gene expression, protecting animals from harm. Since iron ions can accumulate in the substantia nigra neurons of Parkinson's disease patients and thus cause damage, EGCG, which has a strong iron ion chelating function, can partly explain its neuroprotective effect.

2.9 Inhibition of Angiogenesis

Epidemiological studies have shown that the intake of green tea polyphenols can reduce the incidence of diseases such as coronary heart disease and tumors. This beneficial effect is partly derived from its ability to inhibit angiogenesis. Recent research on green tea polyphenols has focused on its prevention of arteriosclerotic lesions by inhibiting neovascularization; that is, its ability to upregulate high-density lipoprotein levels, prevent low-density lipoprotein oxidation, activate platelets, express prothrombin, and express pre-atherosclerotic molecules such as monocyte chemotactic factor-1 and vascular cell tissue factor.

The formation of neovascularization not only promotes the development of arteriosclerotic lesions in the human body but also promotes the development of tumors. Although green tea polyphenols have shown anti-angiogenesis characteristics in many in vitro experiments, there is currently less research on their anti-angiogenesis effects in vivo.

MaitiTK (2003) found that angiogenesis was significantly inhibited after green tea polyphenols were applied to the chicken embryo chorioallantoic membrane. The number and length of small blood vessels were significantly reduced after 48 hours of incubation. In a mouse corneal experimental model, it was discovered that the concentration range of EGCG anti-angiogenesis was 0.1~0.3uM.

Therefore, after moderate consumption of green tea, the blood concentration of green tea polyphenols in the body may reach a level that inhibits angiogenesis. Recent in vivo and in vitro studies on green tea polyphenols have shown that it can inhibit the activity of two proangiogenic factors: VEGF and MMP-2, and prevent the proliferation, and migration of endothelial cells and vascular smooth muscle cells, thereby exerting anti-angiogenesis effects. This helps explain why moderate green tea consumption can reduce the incidence of coronary heart disease and tumors.

2.10 Anti-aging Function

GTP has strong antioxidant and anti-free radical functions, which can delay aging. DNA methylation is a gene modification that can affect gene expression. This will inevitably affect cell differentiation, canceration, and aging. There are studies on the effect of GTP on the specific activity of liver methyltransferase in mice (with ginseng as a control). After 8 weeks of drinking the test concentration of GTP and 2% ginseng, the specific activity of hepatic DNA methyltransferase in the treatment group was higher than that in the normal control group. This indicates that GTP can significantly increase the activity of DNA methyltransferase in mouse liver.

The Elderly Are Drinking Tea

2.11 Anti-hyperhomocysteinemic Effects

Among the diseases listed as the first few causes of death, circulatory system diseases such as heart disease and stroke are among the top. As a risk factor for these diseases, blood total hyperhomocysteine ​​concentration has received much attention. Hyperhomocysteinemia is closely related to the pathogenesis of cardiovascular diseases and can also be a risk factor for neurodegenerative diseases. A study reported the correlation between the total hyperhomocysteine ​​concentration in the blood of elderly people and the daily consumption of green tea. The results showed a significant inverse correlation between the amount of polyphenols consumed per day and the total hyperhomocysteine ​​concentration in the blood. Although it is currently unclear why green tea can inhibit hyperhomocysteinemia, we have sufficient reason to believe that vitamin B6, vitamin B12, and folic acid in green tea components may inhibit hyperhomocysteine ​​content. This shows that green tea is very beneficial to the elderly.

2.12 Detoxification Effects on Heavy Metal Salts and Alkaloid Poisoning

Severe environmental pollution has apparent toxic effects on human health. It has been proven that excessive lead can cause lead poisoning, which can reduce immunity and shorten life. Excessive intake of mercury can damage the kidneys and nervous system. Experiments have shown that tea polyphenols are robust chelators of metal ions, have a strong adsorption effect on heavy metals, can form complexes with heavy metals to produce precipitates, and help reduce the toxic effects of heavy metals on the human body. Besides, tea polyphenols can also improve liver function and are diuretic, so they have a good detoxification effect on alkaloid poisoning.

2.13 Protection Against Radiation Damage

In the 1950s, Japan found that the survivors of the Hiroshima atomic bomb explosion who moved to the tea area and drank high-quality green tea not only survived but also had good health. This fact-finding investigation discovered that tea is a promising radiation antidote. Tea polyphenols have an excellent anti-radiation function, can absorb radioactive substances, and prevent their spread in the human body. They are known as natural ultraviolet filters. Tea polyphenols can block ultraviolet rays and eliminate ultraviolet-induced free radicals, thereby protecting the normal function of melanocytes and inhibiting the formation of melanin. At the same time, it inhibits lipid oxidation and reduces pigmentation.

2.14 Prevention of Dental Caries and Tooth Decay and Elimination of Bad Breath

Tea polyphenols can kill lactobacilli and other cariogenic bacteria in the crevices of the teeth. The compounds inhibit the activity of glucosyltransferase, preventing glucose from polymerizing on the bacterial surface. In this way, pathogens cannot adhere to the teeth, interrupting the formation of dental caries. Residual protein food in the crevices of the teeth becomes a substrate for the growth of spoilage bacteria. Tea polyphenols can kill such bacteria, thus exhibiting the effect of eliminating bad breath.

Disclaimer:

The information provided in this article is intended for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

While efforts have been made to ensure the accuracy and reliability of the information presented, the authors and publishers cannot guarantee its completeness, timeliness, or applicability to any specific situation. The information in this article is derived from various sources, including the internet, popular science magazines, and scientific studies. It is essential to note that scientific research is ongoing, and new findings may emerge that could impact the conclusions or recommendations presented in this article.