title: Short-term effects of polyphenol-rich black tea on blood pressure in men and women.
abstract: There is increasing evidence that black tea polyphenols contribute to vascular health. We have recently shown that regular ingestion of polyphenol-rich black tea over 6 months results in lower systolic and diastolic blood pressure. However, the time course of these effects remains unclear. Therefore, our objective was to determine if short-term effects of tea on blood pressure could contribute to longer-term benefits of regular tea consumption on blood pressure. Men and women (n = 111) were recruited to a randomised placebo-controlled double-blind parallel designed trial. During a 4-week run-in, all participants consumed 3 cups per day of black tea. Participants then consumed 3 cups over 1 day of either powdered black tea solids containing 429 mg of polyphenols (tea), or a control product matched in flavour and caffeine content but containing no tea solids. The 24 h ambulatory blood pressure and heart rate was measured at the end of the 4-week run-in (baseline) and again during the 24 h intervention period. The 24 h day-time and night-time blood pressures were not significantly different between tea and control (P > 0.05). Baseline-adjusted net effects on mean 24 h ambulatory blood pressure for systolic and diastolic blood pressure were -0.2 mm Hg (95% CI, -1.5 to 1.0), P = 0.72, and 0.0 mm Hg (95% CI, -1.0 to 0.9), P = 0.95, respectively. Heart rate was significantly lower for tea compared to control during the night-time and early-morning periods (-2.0 (95% CI, -3.2, -0.8) bpm, and -1.9 (95% CI, -3.7, -0.2) bpm, respectively; P < 0.05 for both), but not during the day-time. These results suggest that the longer-term benefits of black tea on blood pressure are unlikely to be due to short-term changes.
authors.affiliation: School of Medicine and Pharmacology, University of Western Australia, Royal Perth Hospital Unit, GPO Box X2213, Perth, Western Australia 6847, Australia. Jonathan.Hodgson@uwa.edu.au
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Hodgson
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Woodman
authors.forename: Ian B
authors.initials: IB
authors.lastname: Puddey
authors.forename: Theo
authors.initials: T
authors.lastname: Mulder
authors.forename: Dagmar
authors.initials: D
authors.lastname: Fuchs
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Croft
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059808:Polyphenols / Q000737:chemistry* / Q000494:pharmacology*; D013662:Tea / Q000737:chemistry*
chemical_list: D059808:Polyphenols; D013662:Tea