A nitrate-rich vegetable intervention elevates plasma nitrate and nitrite concentrations and reduces blood pressure in healthy young adults

Background
Emerging evidence suggests that increasing dietary nitrate intake may be an effective approach to reduce blood pressure. Beetroot juice is often used to supplement dietary nitrate, whereas nitrate intake levels from habitual diet are low. An increase in the habitual intake of nitrate-rich vegetables may represent an alternative to nitrate supplementation. However, the effectiveness and acceptability of a nitrate–rich-vegetables diet remain to be established.

Objective
The aim was to investigate the effect and feasibility of two different intervention strategies to increase dietary nitrate intake, on plasma nitrate/nitrite concentrations and blood pressure.

Design
A randomized, crossover trial was used.

Participants
Participants were healthy men and women (both n=15; age: 24±6 years) from the Netherlands.

Intervention
Participants were instructed to consume ∼400 mg nitrate at lunch, provided through nitrate-rich vegetables and dietary counseling, or beetroot juice supplementation. Both interventions lasted 1 week, with 1-week washout (January to April 2017).

Main outcome
Plasma nitrate and nitrite concentrations and resting systolic and diastolic blood pressure were measured in an overnight fasted state (before and after intervention) and ∼2.5 hours after lunch (before and throughout intervention on day 1, 4, and 7).

Statistical analysis
Two-factor (time × treatment) repeated-measures analyses of variance were performed.

Results
Mean plasma nitrate concentrations increased with both interventions, with a larger increase in beetroot juice vs nitrate-rich vegetables, both in a fasted state and ∼2.5 hours after lunch (day 1, beetroot juice: 2.31±0.56 mg/dL [373±90 μmol/L] vs nitrate-rich vegetables: 1.71±0.83 mg/dL [277±134 μmol/L]; P<0.001). Likewise, mean plasma nitrite concentrations increased with both interventions, but were higher after lunch in beetroot juice than in nitrate-rich vegetables (day 1: 2.58±1.52 μg/dL [560±331 nmol/L] vs 2.15±1.21 μg/dL [468±263 nmol/L]; P=0.020). Fasting mean systolic and diastolic blood pressure did not change, but mean systolic and diastolic blood pressure assessed ∼2.5 hours after lunch were significantly reduced throughout both intervention periods (P<0.05), with no differences between beetroot juice and nitrate-rich vegetables (day 1, systolic blood pressure: –5.1±9.5 mm Hg and diastolic blood pressure: –5.3±8.9 mm Hg).

Conclusion
Short-term consumption of dietary nitrate in the form of nitrate-rich vegetables represents an effective means to increase plasma nitrate and nitrite concentrations, and reduces blood pressure to the same extent as beetroot juice supplementation.