Green tea, made from the Camellia sinensis plant, is loaded with antioxidants and various substances that are beneficial for health. Polyphenols seem to be responsible for many of the benefits of green tea. Green tea is rich in polyphenol flavonoids including catechins. Epigallocatechin 3-gallate (EGCG) is the most abundant and potent green tea catechin(4). Polyphenols might be able to prevent inflammation and swelling, protect cartilage between the bones, and lessen joint degeneration. They also seem to be able to fight human papilloma virus (HPV) infections and reduce the growth of abnormal cells in the cervix (cervical dysplasia). Research cannot yet explain how this works(1), (4).
Being severely overweight or obese is associated with major health risks such as cardiovascular disease, diabetes, nonalcoholic fatty liver disease, and cancer(5). Many studies have shown that green tea can increase fat burning and help you lose weight(3). A meta-analysis demonstrated long-term intake (3-23 wks) of green tea extract (GTE) reduced body weight in obese and overweight individuals(6). Acute GTE ingestion can increase fat oxidation during moderate-intensity exercise and can improve insulin sensitivity and glucose tolerance in healthy young men(7). One double-blind study of 56 obese, hypertensive subjects found that after taking green tea extract (GTE) for three months compared to a placedo: both systolic and diastolic blood pressures had significantly decreased; considerable reductions in fasting serum glucose and insulin levels and insulin resistance were observed; total antioxidant status increased; and significant decreases in the total and low density lipoprotein (LDL - bad) cholesterol and triglycerides, but an increase in high-density lipoprotein (HDL - good) cholesterol(2).
Autophagy is a process that degrades accumulated and unnecessary intracellular materials, and requires a number of molecules that interact in a highly organized manner to help determine cell survival or death. Polyphenols such as EGCG and resveratrol can induce autophagy and may contribute to anti-aging that mimics the effects of calorie restriction(4).
Green tea has been taken for numerous conditions including depression, non-alcoholic fatty liver disease, inflammatory bowel disease, weight loss, stomach disorders, vomiting, diarrhea, headaches, and osteoporosis. Some people take green tea to prevent various cancers, including breast cancer, prostate cancer, colon cancer, gastric cancer, lung cancer, liver cancer, solid tumor cancers, leukemia, and skin cancer related to exposure to sunlight. Some women use green tea to fight human papilloma virus (HPV), which can cause genital warts, the growth of abnormal cells in the cervix (cervical dysplasia), and cervical cancer. Green tea is also taken for Parkinson's disease, diseases of the heart and blood vessels, diabetes, chronic fatigue syndrome (CFS), dental cavities (caries), kidney stones, and skin damage(1).
Rheumatoid arthritis (RA) is a chronic inflammatory disease of the joints in which systemic overproduction of pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) may accelerate cardiovascular (CV) complications(3). Studies suggest GTE may lower serum tumor necrosis factor α and C-reactive protein(2), (3), and may possess potent joint protective and anti-inflammatory action against RA by lowering disease activity parameters and improving HA and IL-6(7).
1)WebMD. Find a Vitamin or Supplement: GREEN TEA. 2005-2016. http://www.webmd.com/vitamins-supplements/ingredientmono-960-green+tea.aspx?activeIngredientId=960&activeIngredientName=green+tea&source=1
2)Bogdanski P, Suliburska J, Szulinska M, Stepien M, Pupek-Musialik D, Jablecka A. Green tea extract reduces blood pressure, inflammatory biomarkers, and oxidative stress and improves parameters associated with insulin resistance in obese, hypertensive patients. Nutrition research. 2012 Jun 30;32(6):421-7. https://www.researchgate.net/profile/Pawel_Bogdanski/publication/233751738_Green_teaEffects_of_green_tea_supplementation_on_elements_total_antioxidants_lipids_and_glucose_values_in_the_serum_of_obese_patients/links/0912f50b205e230b46000000.pdf
3)Riegsecker S, Wiczynski D, Kaplan MJ, Ahmed S. Potential benefits of green tea polyphenol EGCG in the prevention and treatment of vascular inflammation in rheumatoid arthritis. Life sciences. 2013 Sep 3;93(8):307-12. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768132/
4)Kim HS, Quon MJ, Kim JA. New insights into the mechanisms of polyphenols beyond antioxidant properties; lessons from the green tea polyphenol, epigallocatechin 3-gallate. Redox biology. 2014 Dec 31;2:187-95. http://www.sciencedirect.com/science/article/pii/S2213231714000056
7)Gabr SA, Alghadir AH, Ghoniem GA, Zhang XW, Choe YH, Park YJ, Kim BS. Regulation of cartilage and inflammatory biomarkers in rheumatoid arthritis patients treated with green tea therapy. African Journal of Pharmacy and Pharmacology. 2014 Mar 15;8(10):263-73. http://www.academicjournals.org/journal/AJPP/article-full-text-pdf/9A9232C43688
5)P. G. Kopelman, “Obesity as a medical problem,” Nature. 2000 Apr 6; 404(6778): 635–643. http://www.nature.com/nature/journal/v404/n6778/full/404635a0.html
6)Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. The American journal of clinical nutrition. 1999 Dec 1;70(6):1040-5. https://www.houdeasianart.com/Teainfo/Health/Green_tea_fat_oxidation.pdf
7)Venables MC, Hulston CJ, Cox HR, Jeukendrup AE. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans. The American journal of clinical nutrition. 2008 Mar 1;87(3):778-84. http://www.teavigoinfo.com/pdf/study-12.pdf