February 27, 2010

Effects of encapsulated green tea and Guarana extracts containing a mixture of epigallocatechin-3-gallate and caffeine on 24 h energy expenditure and

Sonia Be´rube´-Parent, Catherine Pelletier, Jean Dore´ and Angelo Tremblay*
Division of Kinesiology, Laval University, Ste-Foy, Que´bec, Canada, G1K 7P4
(Received 7 October 2004 – Revised 8 April 2005 – Accepted 11 April 2005)

It has been reported that green tea has a thermogenic effect, due to its caffeine content and probably also to the catechin, epigallocatechin-3-gallate (EGCG).The main aim of the present study was to compare the effect of a mixture of green tea and Guarana extracts containing a fixed dose of caffeine and variable doses of EGCG on 24 h energy expenditure and fat oxidation. Fourteen subjects took part to this randomized, placebo-controlled, double-blind, cross-over study. Each subject was tested five times in a metabolic chamber to measure 24 h energy expenditure, substrate oxidation and blood pressure. During each stay, the subjects ingested a capsule of placebo or capsules containing 200mg caffeine and a variable dose of EGCG (90, 200, 300 or 400 mg) three times daily, 30 min before standardized meals. Twenty-four hour energy expenditure increased significantly by about 750 kJ with all EGCG–caffeine mixtures compared with placebo. No effect of the EGCG–caffeine mixture was observed for lipid oxidation. Systolic and diastolic blood pressure increased by about 7 and 5 mmHg, respectively, with the EGCG–caffeine mixtures compared with placebo. This increase was significant only for 24 h diastolic blood pressure. The main finding of the study was the increase in 24 h energy expenditure with the EGCG–caffeine mixtures. However, this increase was similar with all doses of EGCG in the mixtures.

Green tea is one of the most widely consumed beverages in the world and is currently perceived as a healthy drink. Green tea contains a large amount of catechins (30 to 42% dry weight), a group of very active flavonoids (Yang & Landau, 2000; Dusfresne & Farnworth, 2001). The catechins, which are antioxidants, have been attributed beneficial health properties such as protection against CVD and certain types of cancer. Also, some attention has recently been given to the possible beneficial effects of green tea on the treatment of obesity. The catechins epicatechin, epicatechin-3-gallate, epigallocatechin and epigallocatechin-3-gallate (EGCG) are the major components of green tea leaves. EGCG is the most abundant catechin and has received the most attention (Yang & Landau, 2000). Caffeine represents approximately 3 to 5% of the dry weight of green tea (Yang & Landau, 2000; Dusfresne & Farnworth, 2001). Caffeine consumption has been related to an increase in energy expenditure (Astrup et al. 1990; Dulloo et al. 1989), which explains why the thermogenic effect of green tea is generally attributed to its caffeine content. However, Dulloo et al. (2000) reported that, in rats, a green tea extract stimulates brown adipose tissue thermogenesis to a much greater extent than that which can be attributed to its caffeine content per se. In another study, ten healthy men were assigned to three treatments: green tea extract containing 50 mg caffeine and 90 mg EGCG, caffeine (50 mg) or placebo. A capsule of green tea extract, caffeine or placebo was taken with each meal. Ingestion of green tea extract increased 24 h energy expenditure by 4% (328 kJ), reflecting its stimulatory effect on thermogenesis. The study also found a reduction in RQ during the green tea extract treatment, suggesting an increase in fat oxidation (Dulloo et al. 1999). On the other hand, the caffeine treatment did not produce any effect on these variables. In addition, the thermogenesis and fat oxidation stimulation obtained in that study was not accompanied by an increase in heart rate that may be seen when patients are treated with sympathomimetic anti-obesity drugs. Since obese individuals are at greater risk of developing cardiac problems, the increase in heart rate and blood pressure frequently observed when treated with sympathomimetic agents is a matter of concern for health professionals. In this context, the green tea extract and caffeine mixture seems to have potential as an effective alternative to these anti-obesity drugs. Since it was shown that a total daily dose of 270 mg (3 £ 90 mg) EGCG combined with a total daily dose of 150 mg (3 £ 50 mg) caffeine has the potential to produce an
increase in energy expenditure, augmenting the amount of caffeine in the blend could possibly accentuate this increase. Moreover, augmenting the amount of EGCG in the green tea extract mixture may produce a greater increase in energy expenditure. If so, the most effective level of EGCG to use in combination with caffeine to produce a significant increase in energy expenditure and fat oxidation without producing negative cardio-stimulatory side-effects would deserve specific investigation.

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