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

  • 2013-05
  • The American journal of clinical nutrition 97(5)
    • Jonathan M Hodgson
    • Kevin D Croft
    • Richard J Woodman
    • Ian B Puddey
    • Dagmar Fuchs
    • Richard Draijer
    • Elena Lukoshkova
    • Geoffrey A Head

Study Design

Type
Randomized Controlled Trial (RCT)
Sample size
n = 111
Population
Men and women (n = 111) with systolic blood pressure between 115 and 150 mm Hg at screening
Methods
randomized, controlled, double-blind, 6-mo parallel-designed trial; participants consumed 3 cups/d of either powdered black tea solids (tea) or a flavonoid-free caffeine-matched beverage (control)
Blinding
Double-blind
Duration
6 mo
Funding
Unclear
  • Large Human Trial

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.

Design

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.

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