title: Black tea lowers the rate of blood pressure variation: a randomized controlled trial.
abstract: BACKGROUND
  Measures of blood pressure variation have been associated with cardiovascular disease and related outcomes. The regular consumption of black tea can lower blood pressure, but its effects on blood pressure variation have yet to be investigated.
  
  
  OBJECTIVE
  We aimed to assess the effects of black tea consumption on the rate of ambulatory blood pressure variation.
  
  
  METHODS
  Men and women (n = 111) with systolic blood pressure between 115 and 150 mm Hg at screening were recruited in a randomized, controlled, double-blind, 6-mo parallel-designed trial designed primarily to assess effects on blood pressure. Participants consumed 3 cups/d of either powdered black tea solids (tea) or a flavonoid-free caffeine-matched beverage (control). The 24-h ambulatory blood pressure level and rate of measurement-to-measurement blood pressure variation were assessed at baseline, day 1, and 3 and 6 mo.
  
  
  RESULTS
  Across the 3 time points, tea, compared with the control, resulted in lower rates of systolic (P = 0.0045) and diastolic (P = 0.016) blood pressure variation by ~10% during nighttime (2200-0600). These effects, which were immediate at day 1 and sustained over 6 mo, were independent of the level of blood pressure and heart rate. The rate of blood pressure variation was not significantly altered during daytime (0800-2000).
  
  
  CONCLUSIONS
  These findings indicate that a component of black tea solids, other than caffeine, can influence the rate of blood pressure variation during nighttime. Thus, small dietary changes have the potential to significantly influence the rate of blood pressure variation. This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTR12607000543482.
authors.affiliation: School of Medicine and Pharmacology, University of Western Australia, Perth, Australia. jonathan.hodgson@uwa.edu.au
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Hodgson
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Croft
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Woodman
authors.forename: Ian B
authors.initials: IB
authors.lastname: Puddey
authors.forename: Dagmar
authors.initials: D
authors.lastname: Fuchs
authors.forename: Richard
authors.initials: R
authors.lastname: Draijer
authors.forename: Elena
authors.initials: E
authors.lastname: Lukoshkova
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Head
mesh_terms: D000328:Adult; D000368:Aged; D001315:Australia; D001794:Blood Pressure / Q000187:drug effects*; D018660:Blood Pressure Monitoring, Ambulatory; D001835:Body Weight; D002110:Caffeine / Q000008:administration & dosage; D002318:Cardiovascular Diseases / Q000188:drug therapy; D004032:Diet; D004311:Double-Blind Method; D005260:Female; D005419:Flavonoids / Q000008:administration & dosage; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D010936:Plant Extracts / Q000494:pharmacology*; D013662:Tea / Q000737:chemistry*
chemical_list: D005419:Flavonoids; D010936:Plant Extracts; D013662:Tea; D002110:Caffeine