Effects of inorganic nitrate and vitamin C co-supplementation on blood pressure and vascular function in younger and older healthy adults: A randomised double-blind crossover trial

Ammar W Ashor, Oliver M Shannon, Anke-Dorothee Werner, Filippo Scialo, Cameron N Gilliard, Katelyn S Cassel, Chris J Seal, D. Zheng, John C Mathers, Mario Siervo

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Background
Vitamin C and inorganic nitrate have been linked to enhanced nitric oxide (NO) production and reduced oxidative stress. Vitamin C may also enhance the conversion of nitrite into NO.

Aims
We investigated the potential acute effects of vitamin C and inorganic nitrate co-supplementation on blood pressure (BP) and peripheral vascular function. The secondary aim was to investigate whether age modified the effects of vitamin C and inorganic nitrate on these vascular outcomes.

Methods
Ten younger (age 18–40 y) and ten older (age 55–70 y) healthy participants were enrolled in a randomised double-blind crossover clinical trial. Participants ingested a solution of potassium nitrate (7 mg/kg body weight) and/or vitamin C (20 mg/kg body weight) or their placebos. Acute changes in resting BP and vascular function (post-occlusion reactive hyperemia [PORH], peripheral pulse wave velocity [PWV]) were monitored over a 3-h period.

Results
Vitamin C supplementation reduced PWV significantly (vitamin C: −0.70 ± 0.31 m/s; vitamin C placebo: +0.43 ± 0.30 m/s; P = 0.007). There were significant interactions between age and vitamin C for systolic, diastolic, and mean arterial BP (P = 0.02, P = 0.03, P = 0.02, respectively), with systolic, diastolic and mean BP decreasing in older participants and diastolic BP increasing in younger participants following vitamin C administration. Nitrate supplementation did not influence BP (systolic: P = 0.81; diastolic: P = 0.24; mean BP: P = 0.87) or vascular function (PORH: P = 0.05; PWV: P = 0.44) significantly in both younger and older participants. However, combined supplementation with nitrate and vitamin C reduced mean arterial BP (−2.6 mmHg, P = 0.03) and decreased PWV in older participants (PWV: −2.0 m/s, P = 0.02).

Conclusions
The co-administration of a single dose of inorganic nitrate and vitamin C lowered diastolic BP and improved PVW in older participants. Vitamin C supplementation improved PWV in both age groups but decreased systolic and mean BP in older participants only.

Clinical trial registration
Current Controlled Trials (ISRCTN98942199).
Original languageEnglish
Pages (from-to)708-717
Number of pages10
JournalClinical Nutrition
Volume39
Issue number3
Early online date20 Mar 2019
DOIs
Publication statusPublished - Mar 2020
Externally publishedYes

Keywords

  • Dietary nitrate
  • Ascorbic acid
  • Aging
  • Blood pressure
  • Vascular function
  • Arterial stiffness

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