Green Tea Extract
Brief description
Green tea extract comes from the Camellia sinensis plant and has gained popularity in the supplement industry as a fat burner.
GTE concentrations vary from manufacturer so it is important to read the label carefully, they will also contain differing amounts of Epigallocatechin gallate (EGCG) and caffeine*.
Mechanisms:
Green tea has a high concentration of flavonoids, especially catechins – which are potent antioxidants(1). Epigallocatechin is the predominant catechin in green tea and has been found to inhibit lipoprotein oxidation, particularly against LDL-C(2).
GTE can also improve lipid profiles by reducing micellar solubility (molecules that bind to cholesterol in the gut), intestinal (gut) absorption of cholesterol and reduces liver production of cholesterol(3, 4) (rat studies).
*See caffeine post for research on benefits of caffeine.
Evidence base
Cholesterol: A 2022 systematic review (SR) examining 55 randomised studies, found GTE demonstrated small but significant reductions in total cholesterol, LDL-C, fasting blood glucose (FBG) and HbA1c(5). Reductions in HBa1c and FBG are useful markers in reducing the risk of type 2 diabetes.
It also increased HDL-C and interventions lasted more than 12 weeks, examining males & females, with a dose <1000mg/d and BMI 25-29.9kg/m2. Findings were reinforced by large other meta-analyses(6, 7) and also significant in those with type 2 diabetes(8).
Heart disease: Findings from a 2023 SR of cohort studies in east Asia found a reduced risk of coronary heart disease, especially with low-to-moderate consumption(9). Other SR seem to agree with these findings(5, 10).
Obesity: A 2024 SR examined 59 studies (n=3802 participants) and found body mass, body fat percentage, BMI and malondialdehyde (free radical) all significantly reduced with GTE supplementation(11). Additionally, markers of oxidative stress improved, including adiponectin and total antioxidant capacity. A previous SR also confirmed these findings, suggesting body weight, BMI and waist circumference reduced with doses of GTE >800mg/d for up to 12 weeks.
In type 2 diabetes, supplementation of GTE at low dose (<800mg/d) for >8 weeks significantly reduced body weight, BMI and body fat(12).
Recommended serving & duration
GTE with doses of >500mg/d seem to be effective at reducing cholesterol, body weight, and improving heart disease. However, no clear consensus on dosage. Higher doses may convey more significant improvements but may be less well tolerated due to caffeine side effects.
Many studies have examined GTE over 8-12 weeks, so consider longer term usage.
Safety & tolerability
Generally well tolerated, however, if you are caffeine sensitive please use with caution.
Furthermore, it has been reported that there is a risk of liver injury with ECGC concentrations. If you have a history of liver disease, please avoid. Toxicology reports noted a dose range of 140mg-1000mg/d(13).
As with all supplements, if there is ANY doubt as to whether these supplements may be suitable for you, please consult with your healthcare provider as they will have access to your medical history, bloods etc.
References
Asbaghi O, Fouladvand F, Ashtary-Larky D, Bagheri R, Choghakhori R, Wong A, et al. Effects of green tea supplementation on serum concentrations of adiponectin in patients with type 2 diabetes mellitus: a systematic review and meta-analysis. Arch Physiol Biochem. 2023;129(2):536-43.
Coimbra S, Santos-Silva A, Rocha-Pereira P, Rocha S, Castro E. Green tea consumption improves plasma lipid profiles in adults. Nutrition Research. 2006;26(11):604-7.
Haidari F, Shahi MM, Zarei M, Rafiei H, Omidian K. Effect of green tea extract on body weight, serum glucose and lipid profile in streptozotocin-induced diabetic rats. A dose response study. Saudi Med J. 2012;33(2):128-33.
Raederstorff DG, Schlachter MF, Elste V, Weber P. Effect of EGCG on lipid absorption and plasma lipid levels in rats. J Nutr Biochem. 2003;14(6):326-32.
Zamani M, Kelishadi MR, Ashtary-Larky D, Amirani N, Goudarzi K, Torki IA, et al. The effects of green tea supplementation on cardiovascular risk factors: A systematic review and meta-analysis. Front Nutr. 2022;9:1084455.
Xu R, Yang K, Li S, Dai M, Chen G. Effect of green tea consumption on blood lipids: a systematic review and meta-analysis of randomized controlled trials. Nutr J. 2020;19(1):48.
Neyestani TR, Nikooyeh B. A comprehensive overview on the effects of green tea on anthropometric measures, blood pressure, glycemic and lipidemic status: An umbrella review and meta meta-analysis study. Nutr Metab Cardiovasc Dis. 2022;32(9):2026-40.
Asbaghi O, Fouladvand F, Moradi S, Ashtary-Larky D, Choghakhori R, Abbasnezhad A. Effect of green tea extract on lipid profile in patients with type 2 diabetes mellitus: A systematic review and meta-analysis. Diabetes Metab Syndr. 2020;14(4):293-301.
Wang ZM, Zhao D, Wang H, Wang QM, Zhou B, Wang LS. Green tea consumption and the risk of coronary heart disease: A systematic review and meta-analysis of cohort studies. Nutr Metab Cardiovasc Dis. 2023;33(4):715-23.
Tran HH, Mansoor M, Butt SRR, Satnarine T, Ratna P, Sarker A, et al. Impact of Green Tea Consumption on the Prevalence of Cardiovascular Outcomes: A Systematic Review. Cureus. 2023;15(12):e49775.
Asbaghi O, Rezaei Kelishadi M, Larky DA, Bagheri R, Amirani N, Goudarzi K, et al. The effects of green tea extract supplementation on body composition, obesity-related hormones and oxidative stress markers: a grade-assessed systematic review and dose-response meta-analysis of randomised controlled trials. Br J Nutr. 2024;131(7):1125-57.
Asbaghi O, Fouladvand F, Gonzalez MJ, Aghamohammadi V, Choghakhori R, Abbasnezhad A. Effect of Green Tea on Anthropometric Indices and Body Composition in Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis. Complement Med Res. 2021;28(3):244-51.
Oketch-Rabah HA, Roe AL, Rider CV, Bonkovsky HL, Giancaspro GI, Navarro V, et al. United States Pharmacopeia (USP) comprehensive review of the hepatotoxicity of green tea extracts. Toxicol Rep. 2020;7:386-402.
