Data_Sheet_1_A Double-Blind Placebo-Controlled Crossover Study of the Effect of Beetroot Juice Containing Dietary Nitrate on Aortic and Brachial Blood Pressure Over 24 h.docx

Dietary inorganic nitrate in beetroot can act as a source of nitric oxide and has been reported to lower brachial blood pressure (BP). This study examined the effect of inorganic nitrate in beetroot juice on aortic (central) BP acutely and over the subsequent 24-h period. A double blind, randomized, placebo-controlled crossover trial was performed in fifteen healthy, normotensive men and women (age 22–40 years). Participants were randomized to receive beetroot juice containing nitrate (6.5–7.3 mmol) or placebo beetroot juice from which nitrate had been removed (<0.06 mmol nitrate). Effects on aortic systolic BP were measured at 30 min (primary endpoint), 60 min and over a subsequent 24 h period using an ambulatory BP monitor. Carotid-femoral pulse wave velocity (cfPWV) was also measured at 30 min. Following a washout period, the procedure was repeated within 7 days with crossover to the opposite arm of the trial. Compared with placebo, ingestion of beetroot juice containing nitrate lowered aortic systolic BP at 30 min by 5.2 (1.9–8.5) mmHg [mean (95% confidence interval); p < 0.01]. A smaller effect on aortic systolic BP was observed at 60 min. There were minimal effects on brachial BP or cfPWV. Effects on aortic systolic BP were not sustained over the subsequent 24 h and there were no effects on other hemodynamic parameters during ambulatory monitoring. A single dose of beetroot juice containing nitrate lowers aortic BP more effectively than brachial BP in the short term, but the effects are comparatively short-lived and do not persist over the course of the same day.</p

Characteristics of the two ethnic groups.

<p>Values are % (n), mean ± SD, or median (25th, 75th percentile) for skewed data; p values were calculated using the Student’s t-test or the Mann-Whitney U-test for continuous variables and the Chi-squared test for categorical variables. Abbreviations: BMI, body mass index; BP, blood pressure; HbA1c, glycosylated haemoglobin; HDL, high density lipoprotein, HOMA-IR, homeostasis model of the assessment of insulin resistance; WHR, waist hip ratio.</p

Correlations between magnitude and timings of various indices of wave reflection.

<p>AIx, augmentation index; P_b backward pressure, P_b/P_f, the ratio of forward to backward pressure; T_s, the time of the shoulder of the waveform; WRI, wave reflection index. Data are Pearson’s correlation coefficients.</p

Geometrical measures of retinal arterioles by ethnic group.

<p>Values are mean [95% confidence interval] either unadjusted or ^§ following adjustment for age, sex, systolic blood pressure, heart rate and diabetes. Abbreviations: LDR, length diameter ratio.</p

Geometrical measures of retinal venules by ethnic group.

<p>Values are mean [95% confidence interval] either unadjusted or ^§ following adjustment for age, sex, body mass index, systolic blood pressure, heart rate, smoking and diabetes. Abbreviations: AVR, arterio-venular ratio; LDR, length diameter ratio.</p

Characteristics of the individuals studied.

<p>Data for men and women are also shown separately.</p><p>Data are mean (SD); p values were calculated using a Student’s t-test comparing women and men. AIx, augmentation index; BMI, body mass index; cSBP, central systolic pressure; DBP, diastolic blood pressure; HR, heart rate, Pb/Pf, the ratio of forward to backward pressure; SBP, systolic pressure; T₁, the time difference between the foot and the shoulder of the waveform; WRI, wave reflection index.</p

Wave intensity analysis and pressure separation of the 3 different types of pressure waveform.

<p>The three types of pressure waveform (A, B, C) and their respective augmentation indices (AIx) are shown. The magnitude of the pressure and wave intensity traces have been scaled equally to allow comparison of morphology. Three principal wave S, c⁻₁ and D, forward pressure (P_f) backward pressure (P_b) and the shoulder point (P_s) are indicated.</p

Scatterplots of the relationship between age and various indices.

<p>A) Age vs. AIx B) Age vs, Log wave reflection index (WRI) and C) Age vs. peak backward/peak forward pressure (P_b/P_f). Regression lines are derived from data pooled by gender but data points for men (○) and women (•) are indicated separately.</p

Correlations between magnitude and timings of various indices of wave reflection and height.

<p>AIx, augmentation index; P_b backward pressure; P_b/P_f, the ratio of forward to backward pressure; T_s, the time of the shoulder of the waveform; WRI, wave reflection index. Data are Pearson’s correlation coefficients. Data are Pearson’s correlation coefficients.</p

Scatterplots of the relationship between age and wave or waveform timings.

<p>A) time of the shoulder (Ts), B) time of the peak of the reflected wave, c⁻₁ and C) time of P_b. Regression lines are derived from data pooled by gender but data points for men (○) and women (•) are indicated separately.</p