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Acute black tea consumption improves cutaneous vascular function in healthy middle-aged humans.

  • 2018-02
  • Clinical nutrition (Edinburgh, Scotland) 37(1)
    • Kirsty A Woodward
    • Nicola D Hopkins
    • Richard Draijer
    • Young de Graaf
    • David A Low
    • Dick H J Thijssen

Study Design

Type
Randomized Controlled Trial (RCT)
Population
Twenty healthy participants (58 ± 5 y, 9 men)
Methods
Randomised, controlled, double-blind, cross-over design; participants ingested a single dose of 200 ml black tea or placebo, followed by assessment of forearm cutaneous perfusion using laser-Doppler flowmetry (LDF) and full-field laser perfusion imaging (FLPI) during three heating protocols
Blinding
Double-blind
Duration
single dose (acute)

Background & aims

Dietary flavonoids, such as those present in black tea, are associated with reduced risk of cardiovascular disease (CVD), possibly through improving nitric oxide (NO) mediated vascular function. The aim of this study was to examine the effect of acute black tea ingestion on cutaneous microvascular function.

Methods

Twenty healthy participants (58 ± 5 y, 9 men) attended two experimental trials (tea, placebo), 7-days apart in a randomised, controlled, double-blind, cross-over design. Participants ingested a single dose of 200 ml black tea or placebo, followed by assessment of forearm cutaneous perfusion using laser-Doppler flowmetry (LDF) using three distinct heating protocols, enabling us to distinguish between axon- and endothelium-dependent vasodilation: 1. rapid 42°C, 2. rapid 39°C and 3. gradual 42°C. On the contralateral arm, full-field laser perfusion imaging (FLPI) was used to assess forearm perfusion during gradual 42°C. Data were presented as cutaneous vascular conductance (CVC; flux/mean arterial pressure, MAP) and CVC expressed as a percentage of maximal CVC (%CVCmax).

Results

Rapid local heating to 39°C or 42°C demonstrated no effect of tea for flux, CVC or %CVCmax (all P > 0.05). Gradual local heating to 42 °C, however, produced a higher skin blood flow following black tea ingestion for absolute CVC (P = 0.04) when measured by LDF, and higher absolute flux (P < 0.001) and CVC (P < 0.001) measured with FLPI. No effect of tea was found for %CVCmax when assessed by either LDF or FLPI.

Conclusions

Acute tea ingestion enhanced cutaneous vascular responses to gradual local heating to 42 °C in healthy, middle-aged participants, possibly through a mechanism related to activation of endothelium-derived chemical mediators, such as NO. These improvements may contribute to the cardiovascular health benefits of regular tea ingestion.

Research Insights

  • Black Tea→Improved Cutaneous Microvascular Function

    Gradual local heating to 42 °C, however, produced a higher skin blood flow following black tea ingestion for absolute CVC (P = 0.04) when measured by LDF, and higher absolute flux (P < 0.001) and CVC (P < 0.001) measured with FLPI.

    Effect
    Beneficial
    Effect size
    Small
    Dose
    200 ml
  • Black Tea→Improved Vascular Conductance

    No effect of tea was found for %CVCmax when assessed by either LDF or FLPI.

    Effect
    Neutral
    Effect size
    Small
    Dose
    200 ml
  • Black Tea→Increased Skin Blood Flow

    Rapid local heating to 39°C or 42°C demonstrated no effect of tea for flux, CVC or %CVCmax (all P > 0.05).

    Effect
    Neutral
    Effect size
    Small
    Dose
    200 ml
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