Effects of dietary inorganic nitrate on blood pressure during and post-exercise recovery: A systematic review and meta-analysis of randomized placebo-controlled trials

Abstract

Objectives: A systematic review with meta-analysis was completed to study the effects of dietary inorganic nitrate (NO₃^-) oral ingestion from vegetables and salts on blood pressure responses during and following exercise.

Background: NO₃^- is a hypotensive agent with the potential to reduce blood pressure peaks during exercise and amplify exercise-induced hypotensive effects. Several randomized and controlled trials have investigated the effects of NO₃^- on hemodynamic responses to physical exercise, however this still has yet to be studied systematically.

Methods: The searches were conducted on EMBASE, Medline, and SPORTSDiscus databases. The study included masked randomized controlled trials (RCTs) with participants ≥18 years old. The NO₃^-intervention group received at least 50 mg NO₃^-/day with similar sources amid NO₃^- and placebo conditions. Included studies reported systolic blood pressure (SBP) or diastolic blood pressure (DBP) values during or following exercise performance.

Results: 1903 studies were identified, and twenty-six achieved the inclusion criteria. NO₃^- daily dosages ranged from 90 to 800 mg/day. Throughout exercise, SBP had smaller increases in the NO₃^- group (-2.81 mmHg (95%CI: -5.20 to -0.41), p=0.02. DBP demonstrated lower values in the NO₃^- group (-2.41 mmHg (95%CI: -4.02 to -0.79), p=0.003. In the post-exercise group, the NO₃^- group presented lower SBP values (-3.53 mmHg (95%CI: -5.65 to 1.41), p=0.001, while no changes were identified in DBP values between NO₃^- and placebo groups (p=0.31). Subgroup meta-analysis revealed that SBP baseline values, exercise type, duration of NO₃^- ingestion, and its dosages mediated blood pressure responses during and following exercise.

Conclusions: NO₃^- ingestion prior to exercise attenuated the increases in SBP and DBP during exercise, and increased the decline in SBP after exercise. These results are dependent on factors that moderate the blood pressure responses (e.g., health status, type of exercise, resting blood pressure values).

Keywords: Cardiovascular responses to exercise; Hemodynamic monitoring; Nitric oxide; Nitrite; Post-exercise hypotension.