Green tea, containing catechins as the main antioxidant agents, has anti-inflammatory and anticancer properties. The number of hydroxyl groups and specific structural groups in the catechins determine their antioxidant activity. Unfermented green tea is the best source of these compounds, with different types and origins of green tea leaves having varying antioxidant properties. Catechins can neutralize reactive oxygen and nitrogen species and include epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate, with the latter having the most potent anti-inflammatory and anticancer potential. Green tea catechins are efficient in preventing several cancers, such as lung, breast, esophageal, stomach, liver, and prostate cancers. Green tea catechins cannot replace standard chemotherapy, but they can support it with their beneficial effects.
Green tea, derived from the Camellia sinensis plant, is one of the oldest and most popular drinks worldwide. Its classification is based on its production tradition, place of origin, and type of soil where the bushes are grown. Green tea is grown in Vietnam, Japan, China, and Taiwan, and its main types include Sencha, Bancha, Matcha, Gyokuro, Mecha, Genmaicha, Kukicha, Kamairicha, Kariganech, Konch, Kokeicha, Fukamushicha, and Tamaryokucha.
The main difference between green tea and black tea is their production process, with green tea having higher catechin content due to the lack of fermentation. Catechins, belonging to the flavonoid group of polyphenols, have strong antioxidant properties, and green tea is a rich source of these compounds.
Catechins have various health-promoting benefits, such as anti-inflammatory, antioxidant, and chemopreventive effects, and may prevent various types of cancers. However, it is important to consider the oxidative potential of catechins when using green tea in the form of dietary supplements.
Health benefits of green tea
Green tea is produced without fermentation, unlike black tea and Oolong, which are partially fermented. Each type of tea has different biologically active ingredients and health-promoting properties. Green tea contains polyphenols, particularly flavonols and flavanols, which have antioxidant and anti-inflammatory effects. Catechins are the dominant polyphenols in green tea, which neutralize free radicals and chelate metal ions in redox reactions. Studies have shown that green tea polyphenols inhibit cell division, induce antioxidant enzymes, and reduce the risk of various cancers. Drinking four glasses of green tea per day for four months reduced urinary levels of 8-hydroxydeoxyguanosine. Green tea may support chemotherapeutic and preventive effects, but it cannot replace pharmacological treatment. Catechins induce cancer cell death without affecting healthy cells.
Chemical composition of green tea
Green tea contains various chemical components including proteins (15-20%), amino acids such as l-theanine, trace elements like magnesium, calcium, copper, zinc, and vitamins B2, B3, C, E, and K. It is also rich in macroelements like fluorine, iodine, and phosphorus. Green tea has xanthine bases such as theophylline and caffeine, pigments like carotenoids and chlorophyll, and phenolic acids like gallic acid. Catechins are the standard green tea flavonoids and are responsible for its antioxidant properties. Different types of catechins have different antioxidant activity. The individual chemical components of green tea have a different effect on different types of cancer.
Health Benefits and Risks of Catechins in Green Tea
EGCG (epigallocatechin gallate) is a well-studied catechin derivative found in green tea, and the amount of catechins in green tea depends on factors such as variety, cultivation, processing, brewing time, and temperature. Catechins have been shown to have numerous beneficial effects, including anti-tumor, antioxidant, anti-inflammatory, anti-microbial, anti-viral, anti-diabetic, anti-obesity, and hypotensive effects. They also act as metal ion chelators and their antioxidant capacity is influenced by their chemical structure. However, under certain conditions, catechins may have pro-oxidative effects, which can be damaging to cellular components and contribute to degenerative diseases and carcinogenesis. Catechins and other active ingredients in green tea can also repair DNA damage caused by UVB radiation and prevent skin damage.
The Anticancer Potential of Green Tea Catechins
Green tea catechins, particularly EGCG (epigallocatechin gallate), have been studied for their potential anticancer effects. EGCG has been found to induce apoptosis and cell cycle arrest in cancer cells, inhibit metalloproteinase activity, and prevent the formation of reactive oxygen species. Studies have also shown that green tea catechins have potential chemo-preventive properties for breast, lung, colorectal, stomach, and liver cancers, and can inhibit cancer stem cells. The anticancer mechanism of EGCG includes inducing both intrinsic and extrinsic apoptotic pathways and activating BAX. Drinking more than ten cups of green tea infusions per day has been linked to a reduction in the incidence of malignant tumors, but consumption of five to nine cups per day has been linked to an increased risk of bladder cancer. The main anticancer mechanism of green tea catechins is the induction of cell cycle arrest and apoptosis.
Green tea vs Black tea
Black tea and green tea have different chemical compositions and processing methods. Black tea contains catechins, theaflavins, phenolic acids, flavanols, tearubigins, amino acids, proteins, methylxanthine, mineral compounds, and volatile substances. Black tea’s polyphenols activate cell death signaling pathways, regulate antioxidant and detoxifying enzymes, and have anti-estrogenic effects that reduce the risk of malignant neoplasms in women. Theaflavin 1 and Theaflavin 2, two theaflavin compounds in black tea, have shown promising results in preventing lung and cervical cancer.
Green tea polyphenols have been shown to have a beneficial effect on cancer prognosis and prevention. In vivo evidence supports their anticancer, anti-viral, anti-bacterial, anti-aging, and hypotensive effects. However, green tea cannot replace standard chemotherapy and should be used as an adjunct. EGCG, the main catechin in green tea, shows promising results in preventing breast, lung, prostate, stomach, and pancreatic cancers.