Clin Nutr Res.  2015 Jul;4(3):160-167. 10.7762/cnr.2015.4.3.160.

Effect of Spinach, a High Dietary Nitrate Source, on Arterial Stiffness and Related Hemodynamic Measures: A Randomized, Controlled Trial in Healthy Adults

• Jovanovski E
• Bosco L
• Khan K
• Au-Yeung F
• Ho H
• Zurbau A
• Jenkins AL
• Vuksan V

• KMID: 2148625
• DOI: http://doi.org/10.7762/cnr.2015.4.3.160

Abstract

Diets rich in fruits and vegetables reduce risk of adverse cardiovascular events. However, the constituents responsible for this effect have not been well established. Lately, the attention has been brought to vegetables with high nitrate content with evidence that this might represent a source of vasoprotective nitric oxide. We hypothesized that short-term consumption of spinach, a vegetable having high dietary nitrate content, can affect the arterial waveform indicative of arterial stiffness, as well as central and peripheral blood pressure (BP). Using a placebo-controlled, crossover design, 27 healthy participants were randomly assigned to receive either a high-nitrate (spinach; 845 mg nitrate/day) or low-nitrate soup (asparagus; 0.6 mg nitrate/day) for 7 days with a 1-week washout period. On days 1 and 7, profiles of augmentation index, central, and brachial BP were obtained over 180 min post-consumption in 4 fasted visits. A postprandial reduction in augmentation index was observed at 180 min on high-nitrate compared to low-nitrate intervention (-6.54 +/- 9.7% vs. -0.82 +/- 8.0%, p = 0.01) on Day 1, and from baseline on Day 7 (-6.93 +/- 8.7%, p < 0.001; high vs. low: -2.28 +/- 12.5%, p = 0.35), suggesting that the nitrate intervention is not associated with the development of tolerance for at least 7 days of continued supplementation. High vs. low-nitrate intervention also reduced central systolic (-3.39 +/- 5.6 mmHg, p = 0.004) and diastolic BP (-2.60 +/- 5.8 mmHg, p = 0.028) and brachial systolic BP (-3.48 +/- 7.4 mmHg, p = 0.022) at 180 min following 7-day supplementation only. These findings suggest that dietary nitrate from spinach may contribute to beneficial hemodynamic effects of vegetable-rich diets and highlights the potential of developing a targeted dietary approach in the management of elevated BP.

Keyword

Vascular; Augmentation index; Blood pressure; Dietary nitrate; Spinach

MeSH Terms

Adult*
Blood Pressure
Cross-Over Studies
Diet
Fruit
Hemodynamics*
Humans
Nitric Oxide
Spinacia oleracea*
Vascular Stiffness*
Vegetables
Nitric Oxide

Figure

• 

  Figure 1 Mean change from baseline in AI75 (%) of high-nitrate versus low-nitrate intervention on (A) Day 1 and (B) Day 7 in 27 healthy participants. Values are expressed as mean ± SEM. An intervention × time interaction was observed on Day 1 (p = 0.03, repeated measures ANOVA). *Significantly different from low-nitrate intervention as assessed by repeated measures ANOVA, p = 0.01.

• 

  Figure 2 Mean change from baseline in central systolic blood pressure on (A) Day 1 and (B) Day 7 and in brachial systolic blood pressure on (C) Day 1 and (D) Day 7 after a high-nitrate or low-nitrate intervention in 27 healthy participants. Values are expressed as mean ± SEM. Different symbols denote a significant effect of high-nitrate compared to low-nitrate intervention as assessed by repeated measures ANOVA. *p = 0.004; †p = 0.025; ‡p = 0.022.

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