Posted on 26 June 2020
Green tea has been studied for a range of health benefits that it exerts primarily through catechins, which belong to a group of plant metabolites called flavonoids. When tea is prepared, catechins are extracted from the leaves into the water. These molecules are antioxidants, and appear to benefit almost every organ system in the body.
Multiple systematic reviews and meta analyses suggest that green tea catechins have varied health benefits. An analysis of 13 studies found a significant reduction in both blood pressure and cholesterol with consumption of green tea or its extract. Other meta analyses suggest that green tea consumption reduces the risk of breast cancer and prostate cancer.
Furthermore, green tea catechins appear to be neuroprotective – its consumption is associated with reduced risk of neurodegenerative disease. This may be because catechins can reduce inflammation, oxidative stress, and the accumulation of harmful proteins in the brain, all of which are associated with neuronal dysfunction.
Green tea catechins appear to be beneficial to the immune system in several ways. Catechins are anti-inflammatory and anti-oxidant molecules, and may reduce background inflammatory processes that are linked with many age-related diseases. Furthermore, epigallocatechin gallate (the most potent green tea catechin) appears to enhance the immune system by increasing the activity of certain immune cells, and some epidemiological studies suggest that green tea protects against respiratory infections.
A meta analysis of 11 studies concluded that consuming epigallocatechin gallate and caffeine led to weight loss, although the extent of the role of caffeine, which may cause weight loss, is unknown. The authors also noted that the results of the 11 studies varied a lot, and so further investigation is needed to firmly conclude that epigallocatechin can promote weight loss.
Green tea appears to be safe in all but the most excessive of doses.
Green tea catechins and blood pressure: a systematic review and meta-analysis of randomised controlled trials: https://doi.org/10.1007/s00394-014-0720-1
Green Tea and the Risk of Prostate Cancer: A Systematic Review and Meta-Analysis: DOI: 10.1097/MD.0000000000006426
A dose-response meta-analysis of green tea consumption and breast cancer risk: https://doi.org/10.1080/09637486.2020.1715353
Beneficial Effects of Green Tea Catechins on Neurodegenerative Diseases: doi: 10.3390/molecules23061297
Effect of Tea Catechins on Influenza Infection and the Common Cold with a Focus on Epidemiological/Clinical Studies.: DOI: 10.3390/molecules23071795
Green Tea Catechin Metabolites Exert Immunoregulatory Effects on CD4(+) T Cell and Natural Killer Cell Activities: DOI: 10.1021/acs.jafc.6b01115
The Effects of Caffeine Intake on Weight Loss: A Systematic Review and Dos-Response Meta-Analysis of Randomized Controlled Trials: DOI: 10.1080/10408398.2018.1507996
Green Tea and Weight Loss:An update (Meta-Analysis): https://www.krishisanskriti.org/vol_image/28Sep20150609355.pdf
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