Effects of Nitrate- and Betalain-Rich Beetroot Juice Ingestion on Vascular Function and Metabolic Syndrome Risk Factors in Healthy Adults: A Pilot Study.

Background/Objectives: Health challenges associated with metabolic syndrome (MetS) have stimulated investigations into the effectiveness of nutraceutical interventions, including beetroot juice (BRJ), in mitigating MetS risk factors. Methods: This repeated-measures crossover trial (n = 16 healthy participants) investigates the effects of daily ingestion of two different BRJs [United Kingdom beetroot juice (UKBR), 1280 mg nitrate, 147 mg betalains; New Zealand beetroot juice (NZBR), 1120 mg nitrate, 506 mg betalains] and placebo (PL) on plasma nitrate and nitrite levels, MetS biomarkers and systemic vascular resistance (SVR). Participants consumed the juices for 6 days, with measures taken on day 7 fasted (pre-dose) and 2 h and 5 h post ingestion (acute). Results: On day 7, pre-dose plasma nitrate levels were significantly elevated for UKBR and NZBR compared to PL (297.2, 177.1 and 64.2 µmol/L, respectively). On day 7, UKBR achieved significantly higher plasma nitrate levels 2 h and 5 h post consumption than NZBR (2 h: 750.3 vs. 577.7 µmol/L; 5 h: 703.4 vs. 510.1 µmol/L) and PL at all timepoints. Plasma nitrite was elevated pre-dose for UKBR only and for both juices relative to PL at 2 h and 5 h. On day 7, pre-dose systolic blood pressure (SBP) was significantly lower for NZBR than PL (-4.96 mmHg) and 2 h post-ingestion for both UKBR (-5.63 mmHg) and NZBR (-4.98 mmHg) compared with PL. Systemic vascular resistance was 11.6% lower after 6 days of consumption of NZBR relative to PL (ratio 0.884, 95% CI 0.803 to 0.974). Conclusions: Supplementation with BRJ reduced SBP relative to placebo, and the betalain-rich NZBR also reduced SVR, whereas the higher-nitrate UKBR did not. This suggests that betalains and nitrates may play an important role in these improvements. The Australia New Zealand Clinical Trials Registry ID for this study is: ACTRN12622000714785.