
Research has reported the benefits of nitrate-rich vegetables, particularly from sources like beetroot, in reducing blood pressure and improving vascular health. This blog highlights a few of these studies.
One study explored how increasing dietary nitrate, particularly through vegetable intake, impacts blood pressure in middle-aged and older adults with (pre)hypertension (blood pressure: 144 ± 13/87 ± 7 mmHg, age: 65 ± 10 years). Over 12 weeks, participants either consumed nitrate-rich vegetables (consume ∼250-300 g nitrate-rich vegetables/day with ∼350-400 mg nitrate/day; n = 25), drank beetroot juice (400 mg nitrate/day; n = 26), or received no intervention (control; n = 26) (1).
Results showed:
Vegetable group: A significant reduction in systolic blood pressure, especially during the day (from 134 ± 10 to 129 ± 9 mmHg).
Beetroot juice group: No significant change in systolic blood pressure (from 138 ± 12 to 137 ± 14 mmHg).
Control group: An increase in systolic blood pressure (from 136 ± 10 to 137 ± 11 mmHg).
This study demonstrated that a 12-week dietary intervention is an effective strategy to increase habitual nitrate-rich vegetable intake (∼250 g/day) and lower systolic blood pressure (by ∼5 mmHg). In contrast, daily supplementation of nitrate via the use of concentrated beetroot juice did not yield the same benefit (1).
Another study examined the effects and feasibility of two strategies to increase nitrate intake—through nitrate-rich vegetables or beetroot juice supplementation—on plasma nitrate/nitrite levels and blood pressure. Using a randomized, crossover design, the trial involved 15 healthy men and 15 women (average age: 24 years) in the Netherlands. Participants consumed around 400 mg of nitrate at lunch via vegetables or beetroot juice for a week, with a one-week washout between interventions (2).
Results showed that both interventions raised plasma nitrate levels, with beetroot juice increasing significantly. Similarly, plasma nitrite levels increased in both cases but were higher after lunch in the beetroot juice group. While fasting blood pressure did not change, blood pressure measured 2.5 hours post-lunch was significantly reduced for both interventions, with no differences between the two strategies. Despite the normal, healthy blood pressure in the current study’s participants, the increased daily nitrate intake significantly reduced systolic blood pressure (~5 mm Hg) and diastolic blood pressure (~3 mm Hg) (2).
This study showed that short-term nitrate intake through vegetables effectively raised plasma nitrate/nitrite levels and reduced blood pressure, comparable to beetroot juice supplementation (2).
The same group of researchers did these two studies (1-2). The authors listed the nitrate-rich vegetables with the nitrate contents that they used in their studies, which you may consider adding to your diet (see below):
Vegetables (raw) Nitrate (mg/100g)
Arugula (rocket salad) 420
Bok choy 325
Rhubarb 294
Lettuce 205
Beetroot 188
Spinach 180
Zucchini 68
Green beans 53
Beetroot is a rich source of nitrate (NO3-) that has been shown to reduce blood pressure. Yet, no studies have examined the vascular benefits of beetroot in whole-food form and whether the effects are modified by age. A four-arm, randomized, open-label, cross-over study was conducted in twenty-four healthy adults (young n=12, age 27 ± 4 years, old n=12, age 64 ± 5 years). Participants consumed whole-cooked beetroots at portions of (NO3- content in brackets) 100 g (272 mg), 200 g (544 mg), and 300 g (816 mg) and a 200-ml solution containing 1000 mg of potassium nitrate (KNO3) on four separate occasions over a 4-week period (≥7-d washout period). Blood pressure, plasma NO3- and nitrite (NO2-) concentrations, and post-occlusion reactive hyperemia via laser Doppler, were measured pre-and up to 5-h post-intervention (3).
Plasma NO2- concentrations were higher in the young vs old at baseline and post-intervention (p < 0·05). All NO3- interventions decreased systolic and diastolic blood pressure in young participants (p < 0·05), whereas only KNO3 (at 240–300 min post-intake) significantly decreased systolic (–4·8 mmHg, −3·5 %, p = 0·024) and diastolic (–5·4 mmHg, −6·5 %, p = 0·007) blood pressure in older participants (3).
The study found a dose-dependent reduction in blood pressure with increasing dietary nitrate in young adults. Higher plasma NO2- levels were linked to a greater blood pressure-lowering effect. Whole-cooked beetroot significantly reduced systolic and diastolic blood pressure in young adults, with the greatest effects seen at higher doses of beetroot and KNO3 (3).
While nitrate increased plasma NO3- and NO2- levels, beetroot did not significantly lower blood pressure in older adults. However, KNO3 did lower blood pressure by 4-5 mmHg, which is considered a meaningful reduction for cardiovascular health. The study found that higher doses of nitrate may be necessary to reduce blood pressure in older adults, and results were more variable than in younger participants. Inconsistent findings in older populations may be due to factors like reduced NO2- -formation, higher levels of reactive oxygen species, or lower availability of nitric oxide. Older adults may also have a reduced capacity to produce NO2- and nitric oxide (NO), potentially due to reduced salivary flow and lower enzyme activity in the mouth (3).
Researchers were interested in more benefits of nitrate-rich vegetables to vascular health, such as whether its intake might prevent blood vessel problems caused by prolonged sitting. One study tested if drinking beetroot juice before sitting could prevent such issues in the legs. Eleven healthy young men (n=7) and women (n=4) participated in two trials: one with a placebo and the other with beetroot juice. They drank either 140 mL of placebo or beetroot juice before sitting for 3 hours. Measurements of leg artery function, blood pressure, and blood were taken before, during, and after sitting (4).
Results showed that blood flow in the leg's popliteal artery dropped in both trials during sitting. In the beetroot juice trial, nitrate and NO levels in the blood increased. While artery function worsened after sitting in the placebo trial, it remained normal in the beetroot juice trial. The study concludes that drinking beetroot juice before sitting can prevent sitting-related blood vessel problems in the legs by boosting NO levels. This suggests that dietary nitrate (from beetroot juice) can help counter the negative effects of prolonged sitting on the vascular system (4).
Peripheral artery disease is characterized by the accumulation of atherosclerotic plaques in the lower extremity conduit arteries, impairs blood flow and walking capacity. Dietary nitrate has been used to reduce blood pressure and improve walking capacity in patients with peripheral artery disease.
One study examined the effects of a body mass-normalized moderate dose of nitrate (0.11 mmol nitrate/kg) as beetroot juice on serum nitrate/nitrite, vascular function, walking capacity, and tissue oxygen utilization capacity in patients with peripheral artery disease. A total of 11 patients with peripheral artery disease received either a nitrate supplement or a placebo in a randomized crossover design. Total serum nitrate/nitrite, resting blood pressure, brachial and popliteal artery endothelial function (flow-mediated dilation), arterial stiffness (pulse-wave velocity), augmentation index, maximal walking distance, and time, claudication onset time, and skeletal muscle oxygen utilization were measured pre-and post-nitrate and placebo intake (5).
There were significant group × time interactions (p < 0.05) for serum nitrate/nitrite, flow-mediated dilation, blood pressure, walking distance and time, and skeletal muscle oxygen utilization. The nitrate group showed significantly increased serum nitrate/nitrite (Δ1.32 μM), increased brachial and popliteal flow-mediated dilation (Δ1.3% and Δ1.7%, respectively), reduced peripheral and central systolic blood pressure (Δ-4.7 mmHg and Δ-8.2 mmHg, respectively), increased maximal walking distance (Δ92.7 m) and time (Δ56.3 s), and reduced deoxygenated hemoglobin during walking. There were no changes in pulse-wave velocity, augmentation index, or claudication. These results indicate that a body-mass-normalized moderate dose of nitrate may be effective and safe for reducing blood pressure, improving endothelial function, and improving walking capacity in patients with peripheral artery disease (5).
To make it relevant to some of you who may want to try out the beetroot juice strategy: in this study, the patients had an average age of 70.0 ± 7.0 years and an average body weight of 77.3 ± 16.5 kg, the average dose of the supplement was ∼0.11 ± 0.01 mmol NO3−/kg, equating to ∼91.8 ± 20.0 mL of the beetroot juice supplement (5).
The studies mentioned here suggested that nitrate-rich vegetables and beetroot juice can effectively increase plasma nitrate/nitrite levels and lead to a reduction in blood pressure, especially in younger adults. However, the effects on older adults may be more variable, and higher doses of nitrate might be necessary to achieve significant blood pressure reduction. Additionally, there is evidence to suggest that dietary nitrate, particularly from beetroot juice, can counter the negative effects of prolonged sitting on the vascular system by boosting nitric oxide levels. Furthermore, dietary nitrate has been investigated for its potential to improve vascular function and walking capacity in patients with peripheral artery disease.
References:
1. van der Avoort CMT, Ten Haaf DSM, Bongers CCWG, van Oorschot F, Verdijk LB, van Loon LJC, Hopman MTE. Increasing Nitrate-Rich Vegetable Intake Lowers Ambulatory Blood Pressure in (pre)Hypertensive Middle-Aged and Older Adults: A 12-Wk Randomized Controlled Trial. J Nutr. 2021 Sep 4;151(9):2667-2679. doi: 10.1093/jn/nxab157. PMID: 34236392.
2. van der Avoort CMT, Jonvik KL, Nyakayiru J, van Loon LJC, Hopman MTE, Verdijk LB. A Nitrate-Rich Vegetable Intervention Elevates Plasma Nitrate and Nitrite Concentrations and Reduces Blood Pressure in Healthy Young Adults. J Acad Nutr Diet. 2020 Aug;120(8):1305-1317. doi: 10.1016/j.jand.2020.02.014. Epub 2020 May 5. PMID: 32386891.
3. Capper T, Clifford T, Taylor G, Iqbal W, West D, Stevenson E, Siervo M. Ageing modifies acute resting blood pressure responses to incremental consumption of dietary nitrate: a randomised, cross-over clinical trial. Br J Nutr. 2023 Feb 14;129(3):442-453. doi: 10.1017/S0007114522001337. Epub 2022 May 5. PMID: 35508923.
4. Morishima T, Iemitsu M, Fujie S, Ochi E. Prior beetroot juice ingestion offsets endothelial dysfunction following prolonged sitting. J Appl Physiol (1985). 2022 Jul 1;133(1):69-74. doi: 10.1152/japplphysiol.00200.2022. Epub 2022 Jun 2. PMID: 35652829.
5. Pekas EJ, Wooden TK, Yadav SK, Park SY. Body mass-normalized moderate dose of dietary nitrate intake improves endothelial function and walking capacity in patients with peripheral artery disease. Am J Physiol Regul Integr Comp Physiol. 2021 Aug 1;321(2):R162-R173. doi: 10.1152/ajpregu.00121.2021. Epub 2021 Jun 23. PMID: 34161745; PMCID: PMC8409914.
Photo by Wendy Wang
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