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Short-term effects of polyphenol-rich black tea on blood pressure in men and women.
MedLine Citation:
PMID:  23038021     Owner:  NLM     Status:  Publisher    
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.
Jonathan M Hodgson; Richard J Woodman; Ian B Puddey; Theo Mulder; Dagmar Fuchs; Kevin D Croft
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-5
Journal Detail:
Title:  Food & function     Volume:  -     ISSN:  2042-650X     ISO Abbreviation:  Food Funct     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-5     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101549033     Medline TA:  Food Funct     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
School of Medicine and Pharmacology, University of Western Australia, Royal Perth Hospital Unit, GPO Box X2213, Perth, Western Australia 6847, Australia.
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