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.
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Korean red ginseng (steam treated Panax ginseng C.A. Meyer), among most prized traditional herbal remedies, has been clinically shown to improve cardiovascular disease (CVD) risk factors. Whether this holds true for the dried non-steamed variety, known as Korean white ginseng (KWG) is unclear. This study therefore, investigated the efficacy and safety of escalating doses of KWG on vascular and glycemic parameters in type 2 diabetes (T2DM). Using an acute, randomized, placebo-controlled, double-blind, crossover design, 25 participants with well-controlled T2DM (12-males: 13-females, age: 63 ± 9 years, A1c: 6.9 ± 0.7%, BMI: 29.3 ± 4.3 kg/m2) underwent five visits during which they received 1 g, 3 g, or 6 g KWG or 3 g wheat-bran control (twice) together with 50 g-glucose load. For the duration of 240 minutes, augmentation index (AI), and central blood pressure were measured at baseline and at 60 min-intervals, and ambulatory blood pressure was assessed at baseline and at 10 min-intervals. Additionally, capillary blood was collected at time zero and at 15, 30, 45, 60, 90, 120, and 180 minutes post-treatment. A symptoms questionnaire was used to assess safety and adverse events. Two-way ANOVA demonstrated a significant time-treatment interaction effect on AI (p = 0.01) with one-way ANOVA showing significant reductions in AI with 3 g KWG relative to control (p = 0.04). Compared to control, acute administration of KWG appeared to be safe, but did not affect any other postprandial, vascular or glycemic parameters. KWG might have a beneficial effect on AI, a cumulative indicator of arterial health. However, these results are preliminary and highlight the need for long-term investigation with a focus on its accountable components. Clinical Trial Registration: NCT01699074
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