Merck
  • Home
  • Search Results
  • Black tea lowers the rate of blood pressure variation: a randomized controlled trial.

Black tea lowers the rate of blood pressure variation: a randomized controlled trial.

The American journal of clinical nutrition (2013-04-05)
Jonathan M Hodgson, Kevin D Croft, Richard J Woodman, Ian B Puddey, Dagmar Fuchs, Richard Draijer, Elena Lukoshkova, Geoffrey A Head
ABSTRACT

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. We aimed to assess the effects of black tea consumption on the rate of ambulatory blood pressure variation. 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. 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). 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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Caffeine, meets USP testing specifications, anhydrous
Sigma-Aldrich
Caffeine, Sigma Reference Standard, vial of 250 mg
Sigma-Aldrich
Caffeine, SAJ special grade, ≥98.5%
Supelco
Caffeine, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Caffeine Melting Point Standard, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Caffeine, anhydrous, 99%, FCC, FG
Sigma-Aldrich
Caffeine, anhydrous, tested according to Ph. Eur.
Supelco
Mettler-Toledo Calibration substance ME 18872, Caffeine, analytical standard, for the calibration of the thermosystem 900, traceable to primary standards (LGC)
Sigma-Aldrich
Caffeine, BioXtra
Supelco
Caffeine, certified reference material, TraceCERT®
Sigma-Aldrich
Caffeine, powder, ReagentPlus®
Caffeine, European Pharmacopoeia (EP) Reference Standard
Supelco
Caffeine solution, analytical standard, 1.0 mg/mL in methanol
Supelco
Melting point standard 235-237°C, analytical standard
Supelco
Caffeine solution, 1.0 mg/mL in methanol, ampule of 1 mL, certified reference material, Cerilliant®
Caffeine for system suitability, European Pharmacopoeia (EP) Reference Standard