Whole beetroot consumption reduces systolic blood pressure and modulates diversity and composition of the gut microbiota in older participants

Abstract

Background: Age-associated decline in physiological function has been identified as the main factor increasing disease risk, including cardiovascular (CVD) and gastrointestinal tract (GIT) diseases. Nutritional interventions encompassing dietary inorganic nitrates, such as nitrate rich beetroot may reduce the risk for CVD and GIT. Objective: Assess the impact of whole beetroot on blood pressure (BP), microbiota profile and functional measures (physical and bowel). Design: Thirty-six healthy participants were recruited (mean age 67 ± 6 years; body mass index (BMI) 25 ± 2 kg/m) and assigned randomly to a beetroot (n = 19) or control group (n = 17). Beetroot group consumed 150 g of whole beetroot and a medium-sized banana and the control group consumed a medium-sized banana every second day for 8 weeks. Resting BP, microbiota profiling, physical activity, urinary nitrate, short-chain fatty acids (SCFA) and Bristol Stool Score (BSS) were measured at 0, 4 and 8 weeks. Plasma nitrate was measured at weeks 0 and 8. Results: The beetroot group had a resting systolic BP reduction of 8.0 mmHg (p = 0.03), lower relative abundance of the phyla Bacteroidetes (p = 0.04), and a higher relative abundance of genus Alistipes (p = 0.03), increased Shannon diversity index (p = 0.03), fibre intake of 7 g/day (p < 0.01), nitrate intake 145 mg/day (p < 0.01), urinary nitrate of 460 μmol/L (p = 0.02) and SCFA concentrations (p < 0.05). However, 8 weeks of beetroot consumption did not have any impact upon functional measures, urine or plasma nitrate and BSS. Conclusion: In a randomised controlled trial, consuming whole beetroot for 8 weeks resulted in modification of risk factors for CVD and GIT disorders in older participants. Physical measures were unaffected and further assessment of more sensitive measures of functional performance are required to ascertain if whole beetroot may offer additional physiological benefits in older populations. Although the data here is promising, further mechanistic studies and larger clinical trials are required to confirm the findings