Daily liquorice consumption for two weeks increases augmentation index and central systolic and diastolic blood pressure

Abstract

Background: Liquorice ingestion often elevates blood pressure, but the detailed haemodynamic alterations are unknown. We studied haemodynamic changes induced by liquorice consumption in 20 subjects versus 30 controls with average blood pressures of 120/68 and 116/64 mmHg, respectively.

Methods: Haemodynamic variables were measured in supine position before and after two weeks of liquorice consumption (daily glycyrrhizin dose 290-370 mg) with tonometric recording of radial blood pressure, pulse wave analysis, and whole-body impedance cardiography. Thirty age-matched healthy subjects maintaining their normal diet were studied as controls.

Results: Two weeks of liquorice ingestion elevated peripheral and central systolic and diastolic blood pressure (by 7/4 and 8/4 mmHg, 95% confidence intervals [CI] 2-11/1-8 and 3-13/1-8, respectively, P<0.05), and increased extracellular volume by 0.5 litres (P<0.05 versus controls). Also augmentation index adjusted to heart rate 75/min (from 7% to 11%, 95% CI for change 0.3-7.5, P<0.05) and aortic pulse pressure (by 4 mmHg, 95% CI 1-7, P<0.05) were elevated indicating increased wave reflection from the periphery. In contrast, peripheral (-3/-0.3 mmHg) and central blood pressure (-2/-0.5 mmHg), aortic pulse pressure (-1 mmHg), and augmentation index adjusted to heart rate 75/min (from 9% to 7%) decreased numerically but not statistically significantly without changes in extracellular volume in the control group. Heart rate, systemic vascular resistance, cardiac output, and pulse wave velocity did not differ between the groups.

Conclusions: Two weeks of daily liquorice consumption increased extracellular volume, amplified pressure wave reflection from the periphery, and elevated central systolic and diastolic blood pressure.

Trial registration: EU Clinical Trials Register EudraCT 2006-002065-39 ClinicalTrials.gov NCT01742702.

Conflict of interest statement

Competing Interests: The funding from the commercial source (Astra Zeneca Plc.) was a relatively small personal research grant to author Miia Leskinen (5000 ). Application to this funding by Astra Zeneca Plc was open nation-wide in Finland for all Ph.D. students doing biomedical research, and the funds were granted on the basis of the present study protocol. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.

Figures

Figure 1. Flow diagram of the study.

Figure 2. Radial and aortic blood pressure, liquorice diet versus normal diet.

Grey lines represent each individual, thick black line represents mean values of each variable. SBP, systolic blood pressure; DBP, diastolic blood pressure; P values between graphs are for the difference in the change of each variable between liquorice diet versus normal diet, P values in brackets are for the change within each group, n = 20 and 30 in the liquorice and normal diet groups, respectively.

Figure 3. Aortic pulse pressure, augmentation index, and pulse wave velocity, liquorice diet versus normal diet.

Grey lines represent each individual, thick black line represents mean values of each variable. P values are for the difference in the change of each variable between liquorice diet versus normal diet, P values in brackets are for the change within each group, n = 20 and 30 in the liquorice and normal diet groups, respectively.

Figure 4. Heart rate, cardiac index, systemic vascular resistance index, liquorice diet versus normal diet.

Grey lines represent each individual, thick black line represents mean change of each variable. P values are for the difference in the change of each variable between liquorice diet versus normal diet, P values in brackets are for the change within each group, n = 20 and 30 in the liquorice and normal diet groups, respectively.