The major green tea catechins are epigallocatechin-3-gallate (EGCG), epigallocatechin (EGC), epicatechin-3-gallate (ECG), and epicatechin (EC). Green tea also provides an array of other bioactive “phytonutrients” such as phenolic acids (gallic acid, chlorogenic acid, and caffeic acid), polyphenol flavonols such as kaempferol, myricetin and quercetin, minerals and trace elements.2
Typical green tea extracts are very poorly absorbed in humans.3 This is where Green Tea Phytosome® has the advantage: its catechin molecules are bonded with phosphatidylcholine, which is very highly bioavailable and therefore will escort or “chaperone” the catechins across the digestive lining and into the blood. EGCG on this phytosome form is at least twice as bioavailable as conventional EGCG.
In a randomized clinical study with 12 healthy young men, half were given a single dose of GreenSelect® PhytosomeTM and the other half were given the same amount of decaffeinated green tea extract but not in phytosome form.4 The peak blood concentration of EGCG from GreenSelect® PhytosomeTM measured at double that of the conventional (non-phytosome) extract. This same study also found that the green tea catechins enhanced blood antioxidant capacity over the conventional green tea catechins.
Versatile Antioxidant Activity*
The four major green tea catechins (EGCG, EGC, ECG, and EC) have different chemical structures, and thus are able to scavenge a variety of free radicals.5,6 Some clinical trials suggest that EGCG may have synergistic effects with other catechins, and that metabolic derivatives of EGCG and perhaps the other catechins may have potent bioactivity.7 Human trials suggest the green tea polyphenols help protect DNA by providing an extra source of dietary antioxidants.8-10 Researchers have proposed that the green tea catechins and their metabolic derivatives have antioxidant actions that are both direct (via scavenging radicals) and indirect (by influencing gene activity and up-regulating antioxidant enzymes).11
Intense physical exercise generates reactive oxygen species (oxygen “free radicals”) that can challenge the body’s antioxidant defenses. In a recent randomized, double-blind, placebo-controlled trial of 35 healthy young men, 17 of them received green tea extract capsules containing 320 mg of polyphenols, while the remaining 18 received a placebo, both for 4 weeks.12 The men performed a short-term muscular endurance test twice—once before and once after the supplementation period. Supplementation with the extract resulted in a significant increase in total blood polyphenols both at rest and 5 minutes after the endurance test, compared to placebo. This polyphenol increase contributed to enhanced blood antioxidant status at rest, suggesting that the green tea catechins can help offset potential oxidative stress from intense exercise in untrained men.
In another recent randomized, double blind, placebo controlled trial, 56 overweight participants received either green tea extract or a placebo with breakfast for 3 months.13 The extract was found to promote healthy metabolic function and a significant increase in total antioxidant status (signifying support against oxidative stress).
Powerful Support for Cardiovascular Health*
Clinical research with green tea increasingly demonstrates its potential to enhance cardiovascular and metabolic health.14 Several epidemiologic studies, most of which examined populations where green tea is commonly consumed, such as in Japan, have reported positive links (“correlations”) between green tea consumption and longstanding cardiovascular health.15 Maintenance of a healthy vascular endothelium (the single cell layer that lines the blood vessel walls) is critical for the health of the circulatory system, and this is an active of research with green tea.
In a few trials that investigated green tea or green tea extracts on vascular function in humans, specific benefits were reported. In one such study 14 healthy women received green tea extract for five weeks.16 The researchers found significant support for brachial artery function. Specifically, its healthy capacity to dilate in response to increased blood flow was significantly increased. Additionally, the green tea extract significantly improved antioxidant support for the blood.
Green Tea Likely Enhances Brain Function*
Epidemiologic (population survey) studies suggest green tea consumption supports brain health. In a study that examined a cross-section of 1,003 elderly Japanese, higher green tea consumption was associated with superior cognitive health.17 Although clinical evidence is limited, in vitro and animal studies have suggested plausible mechanisms for how green tea catechins may support the aging brain.18 As examples, the green tea catechins are effective free radical scavengers and also chelate iron, besides having the capacity to positively influence genes that contribute to brain health.19
Research is accelerating on the potential health benefits of EGCG for the human brain. In a randomized, double blind, placebo-controlled study, 31 young men and women were given a single dose of either a placebo capsule or capsule containing decaffeinated green tea extract (300 mg, high in EGCG.20 Compared to placebo, the extract elicited a significant overall increase in alpha, beta, and theta electrical brain wave activity. The researchers noted that it was remarkable to find increased activity across all 3 of these brain bandwidths. Alpha activity is associated with relaxation, beta activity with focused attention, and resting theta activity with quiet wakefulness. This may in part explain reports that drinking green tea can be relaxing while increasing alertness at the same time.
Other Possible Benefits of Green Tea Extract
The green tea catechins continue to be intensively researched for a range of other potential health benefits, including metabolic enhancement to facilitate healthy weight management. Responsible research trial design will clarify this potential in the future.21
1. Cooper R, Morre DJ, Morre DM. J Altern Complement Med 2005;11:521-8.
Cabrera C, Artacho R, Gimenez R. Journal of the American College of Nutrition 2006;25:79-99.
Lee MJ, Maliakal P, Chen L, others. Cancer Epidemiol Biomarkers Prev 2002;11:1025-32.
Pietta P, Simonetti P, Gardana C, others. Biochem Mol Biol Int 1998;46:895-903.
Zhao B, Guo Q, Xin W. Methods Enzymol 2001;335:217-31.
Moore RJ, Jackson KG, Minihane AM. Br J Nutr 2009;102:1790-802.
Nagle DG, Ferreira D, Zhou YD. Phytochemistry 2006;67:1849-55.
Luo H, Tang L, Tang M, others. Carcinogenesis 2006;27:262-8.
Morley N, Clifford T, Salter L, others. Photodermatol Photoimmunol Photomed 2005;21:15-22.
Erba D, Riso P, Bordoni A, others. J Nutr Biochem 2005;16:144-9.
Weinreb O, Mandel S, Amit T, Youdim MB. J Nutr Biochem 2004;15:506-16.
Jowko E, Sacharuk J, Balasinska B, others. Nutr Res 2011;31:813-21.
Bogdanski P, Suliburska J, Szulinska M, others. Nutr Res 2012;32:421-7.
Wolfram S. J Am Coll Nutr 2007;26:373S-388S.
15. Kuriyama S, Shimazu T, Ohmori K, others. JAMA 2006;296:1255-65.
Tinahones FJ, Rubio MA, Garrido-Sanchez L, others. J Am Coll Nutr 2008;27:209-13.
Kuriyama S, Hozawa A, Ohmori K, others. Am J Clin Nutr 2006;83:355-61.
Weinreb O, Amit T, Mandel S, Youdim MB. Genes Nutr 2009.
Mandel SA, Avramovich-Tirosh Y, Reznichenko L, others. Neurosignals 2005;14:46-60.
Scholey A, Downey LA, Ciorciari J, others. Appetite 2012;58:767-70.
Johnson R, Bryant S, Huntley AL. Maturitas 2012;73:280-7.