title: Effect of moderate intakes of different tea catechins and caffeine on acute measures of energy metabolism under sedentary conditions.
abstract: Green tea may stimulate energy metabolism; however, it is unclear if acute effects are caused by specific catechins, caffeine or their combination. The objective of the present study was to examine the separate and combined effects of different catechins and caffeine on energy expenditure (EE) and fat oxidation over a single day. Fifteen healthy, normal-weight males received capsules containing placebo, caffeine alone (150 mg), or caffeine plus a catechin mixture (600 mg) enriched in either epigallocatechin-3-gallate (EGCG), epigallocatechin or a mix of catechins, in a randomised cross-over double-blinded design. On each test day EE, respiratory quotient (RQ) and substrate oxidation were measured under sedentary conditions in a respiratory chamber for 13.5 h. We found no significant treatment effect on EE (P = 0.20) or RQ (P = 0.68). EGCG with caffeine insignificantly raised EE and fat oxidation v. caffeine-only and placebo (EE 5.71 (SE 0.12) v. 5.68 (SE 0.14) v. 5.59 (SE 0.13) MJ/12.5 h, respectively; fat oxidation 84.8 (SE 5.2) v. 80.7 (SE 4.7) v. 76.8 (SE 4.0) g/12.5 h). Catechin/caffeine combinations at these dosages and mode of application had non-significant acute effects on EE and fat oxidation. The maximum observed effect on EE of about 2 % could still be meaningful for energy balance over much longer period of exposure. However, higher short-term effects reported in the literature may reflect variations in green tea extracts, added caffeine, or synergies with physical activity. The specific mechanisms and conditions that may underpin observed longer-term benefits of catechin-enriched green tea consumption on body composition remain to be confirmed.
authors.affiliation: Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark. ntg@life.ku.dk
authors.forename: Nikolaj T
authors.initials: NT
authors.lastname: Gregersen
authors.forename: Christian
authors.initials: C
authors.lastname: Bitz
authors.forename: Inger
authors.initials: I
authors.lastname: Krog-Mikkelsen
authors.forename: Ole
authors.initials: O
authors.lastname: Hels
authors.forename: Eva M R
authors.initials: EM
authors.lastname: Kovacs
authors.forename: Jane A
authors.initials: JA
authors.lastname: Rycroft
authors.forename: Erik
authors.initials: E
authors.lastname: Frandsen
authors.forename: David J
authors.initials: DJ
authors.lastname: Mela
authors.forename: Arne
authors.initials: A
authors.lastname: Astrup
mesh_terms: D000328:Adult; D001066:Appetite / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D002392:Catechin / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects*; D004837:Epinephrine / Q000652:urine; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009638:Norepinephrine / Q000652:urine; D010084:Oxidation-Reduction; D011659:Pulmonary Gas Exchange / Q000502:physiology; D013662:Tea / Q000737:chemistry*; D055815:Young Adult
chemical_list: D013662:Tea; D002110:Caffeine; D002392:Catechin; D009638:Norepinephrine; D004837:Epinephrine