As far as ECGC, most studies on green tea have been done with consumption of a brewed beverage. However there is a study in the American Journal of Clinical Nutrition that found catechin absorption was enhanced when tea polyphenols were administered in pill form. Green tea thus in supplement form showed enhanced bioavailability compared with that of beverage form.
Research has shown that caffeine and EGCG are synergistic in weight loss. However, Swiss researchers reported green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content alone, and green tea extract causes weight loss through sympathetic activation of thermogenesis, fat oxidation, or both, in a study that measured the 24-hour energy expenditure among 10 healthy men randomly assigned to take either three doses of caffeine (50 mg), green tea extract (containing 50 mg caffeine and 90 mg EGCG), or placebo, on three separate occasions.
Dulloo AG et al. "Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-hour energy expenditure and fat oxidation in humans." Am J Clin Nutr. 70, 6:1040-5, 1999
Here is the abstract...
Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans1,2,3
Abdul G Dulloo, Claudette Duret, Dorothée Rohrer, Lucien Girardier, Nouri Mensi, Marc Fathi, Philippe Chantre and Jacques Vandermander
1 From the Department of Physiology, Faculty of Medicine, University of Geneva; Geneva University Hospital; and Laboratoires Arkopharma, Nice, France.
Background: Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system.
Objective: We investigated whether a green tea extract, by virtue of its high content of caffeine and catechin polyphenols, could increase 24-h energy expenditure (EE) and fat oxidation in humans.
Design: Twenty-four–hour EE, the respiratory quotient (RQ), and the urinary excretion of nitrogen and catecholamines were measured in a respiratory chamber in 10 healthy men. On 3 separate occasions, subjects were randomly assigned among 3 treatments: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner.
Results: Relative to placebo, treatment with the green tea extract resulted in a significant increase in 24-h EE (4%; P < 0.01) and a significant decrease in 24-h RQ (from 0.88 to 0.85; P < 0.001) without any change in urinary nitrogen. Twenty-four–hour urinary norepinephrine excretion was higher during treatment with the green tea extract than with the placebo (40%, P < 0.05). Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines.
Conclusions: Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.
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