Nitric Oxide · Cardiovascular Health · Performance
Nitric Oxide Benefits: What It Does in the Body
Nitric oxide regulates blood vessel dilation, supports healthy blood pressure, influences exercise performance, and plays a role in immune function. The science is more interesting and more nuanced than most supplement labels suggest. Here is what it actually does and what the research shows.
The basics
What nitric oxide is and what it does
Nitric oxide is a gas molecule produced naturally by nearly every cell type in the body. Despite being incredibly short-lived - it breaks down within seconds - it acts as a powerful signalling molecule that triggers responses in surrounding tissues. The endothelial cells lining blood vessels are the primary producers, using an enzyme called endothelial nitric oxide synthase (eNOS) to convert the amino acid L-arginine into nitric oxide and L-citrulline.
The most well-established role of nitric oxide is vasodilation - relaxing the smooth muscle in blood vessel walls, which allows them to widen and increases blood flow. This single function has cascading effects across the cardiovascular system, exercise capacity, sexual function, and brain health. Beyond blood vessels, nitric oxide also acts as a neurotransmitter, modulates immune responses, and influences mitochondrial function. For a deeper look at what happens when NO levels drop, see the guide to signs of nitric oxide deficiency.
When NO is sufficient, arteries relax and blood flows with less resistance. Reduced NO bioavailability is one of the earliest markers of hypertensive vascular disease.
Increased NO during exercise enhances blood flow to working muscles, improving oxygen and nutrient delivery and reducing the oxygen cost of effort.
Adequate NO production protects the endothelium from oxidative damage, reduces arterial stiffness, and helps prevent platelet aggregation and clot formation.
NO-driven vasodilation is the central mechanism in erectile function and plays a role in healthy blood flow to the brain.
Cardiovascular protection
Nitric oxide and blood vessel health
Healthy endothelial function depends on adequate nitric oxide production. When the endothelium is damaged - by oxidative stress, high blood sugar, smoking, or chronic inflammation - NO production drops, vessels become stiffer, and the risk of atherosclerosis increases. Endothelial dysfunction is now considered one of the earliest detectable markers of cardiovascular disease, largely because it reflects declining NO bioavailability.
Supporting NO production through diet, exercise, and targeted supplementation is one of the most direct ways to protect vascular health. For related reading, see the article on magnesium for heart health - magnesium is required for proper eNOS function, and deficiency impairs nitric oxide production.
Blood pressure
Blood pressure regulation is one of nitric oxide's most clinically significant roles. A 2022 meta-analysis published in Frontiers in Nutrition found that nitrate from beetroot juice reduced systolic blood pressure by approximately 5 mmHg in people with hypertension. For a complete overview of blood pressure strategies, see the guide on how to reduce blood pressure and the specific relationship between nitric oxide and blood pressure.
Physical performance
Nitric oxide and exercise performance
During exercise, increased nitric oxide production enhances blood flow to working muscles, improving oxygen and nutrient delivery. A 2021 systematic review and meta-analysis of 118 studies published in the Journal of the International Society of Sports Nutrition found that nitrate-rich foods produced small but significant improvements in endurance exercise performance across time-trial, time-to-exhaustion, and intermittent-type tests. The benefit was consistent in males and in recreational rather than highly trained athletes - elite endurance athletes with very high VO2 max appear to derive less benefit from nitrate supplementation specifically, though polyphenol-rich foods showed benefits at that level.
For athletes, the typical research dose for beetroot juice is around 300-600mg of nitrate, equivalent to roughly 500ml of beetroot juice or a concentrated shot. If low energy is a broader issue, the guide on how to boost energy covers additional strategies. Taurine is another compound worth noting in performance contexts - it supports both blood pressure regulation and nitric oxide production, covered in the article on taurine and NO production.
The mechanisms
How the body makes nitric oxide
The body produces nitric oxide through two main pathways. The L-arginine pathway uses the enzyme eNOS to convert L-arginine into NO in the endothelium - this is the primary pathway and depends on adequate L-arginine, oxygen, and cofactors including BH4 (tetrahydrobiopterin), folate, and vitamin C. The nitrate-nitrite-NO pathway is a backup system that converts dietary nitrate (from vegetables) into nitrite via oral bacteria, and then into NO, particularly in low-oxygen conditions. This second pathway becomes increasingly important with age, as eNOS activity naturally declines.
| Pathway | Source | Key requirements | Practical implication |
|---|---|---|---|
| L-arginine / eNOS | Primary pathway in the endothelium |
L-arginine, oxygen, BH4, folate, vitamin C |
Exercise (shear stress) stimulates eNOS expression; declines with age |
| Nitrate-nitrite-NO | Dietary nitrate from vegetables |
Oral bacteria (disrupted by antiseptic mouthwash) |
Increasingly important backup as eNOS ages; beetroot and leafy greens are key sources |
Antiseptic mouthwash: It kills the oral bacteria needed to convert nitrate to nitrite, blocking the nitrate-nitrite-NO pathway entirely. If you eat nitrate-rich foods for cardiovascular benefit, avoid using antibacterial mouthwash around the same time.
Diet first
Foods that support nitric oxide production
Nitrate-rich vegetables are the most direct dietary source: beetroot, spinach, rocket (arugula), celery, and lettuce are particularly high. L-arginine-rich foods include nuts, seeds, legumes, meat, fish, and dairy. L-citrulline is found in watermelon, particularly the rind. Polyphenol-rich foods including berries, dark chocolate, and pomegranate support NO production by protecting it from oxidative breakdown. For more on protective dietary compounds, see the guide to what antioxidants are and how they work and the article on anti-inflammatory foods.
What reduces nitric oxide production
Several factors reduce the body's ability to produce or maintain nitric oxide. Ageing is the most significant - eNOS activity declines naturally over time. Oxidative stress from smoking, poor diet, or chronic inflammation breaks down NO before it can act. Antiseptic mouthwash disrupts the oral bacteria needed for the nitrate pathway. Sedentary behaviour reduces the shear stress on blood vessel walls that stimulates eNOS activity. And deficiencies in key cofactors - particularly L-arginine, folate, and vitamin C - limit the raw materials needed for NO synthesis.
Supplementation
Nitric oxide supplements - what they actually contain
You cannot supplement nitric oxide directly - it is a gas that breaks down in seconds. What NO supplements actually contain are precursors: compounds that the body converts into nitric oxide. The most common are L-arginine, L-citrulline, and beetroot extract (as a concentrated nitrate source).
L-citrulline is generally preferred over L-arginine for oral supplementation. While L-arginine is the direct precursor to NO, it is heavily metabolised in the gut and liver before reaching systemic circulation. A comprehensive review in the Journal of Strength and Conditioning Research confirmed that oral L-citrulline supplementation effectively raises both plasma arginine and total nitrate/nitrite concentrations, outperforming equivalent doses of L-arginine for sustained plasma arginine levels.
Magnesium also plays a supporting role - it is required for proper eNOS function, and deficiency impairs NO production. The evidence base for magnesium includes cardiovascular and vascular benefits that operate through this shared pathway.
Who benefits most from supplementation: People with poor endothelial function, elevated blood pressure, low dietary nitrate intake, or those over 50 where eNOS activity has naturally declined. For people eating leafy greens and beetroot regularly, with good exercise habits and no blood pressure concerns, food-first is likely sufficient.
Supplements vs habits
Supplements work best when they sit on top of solid health habits, not as a replacement for them. Regular aerobic exercise is one of the most potent natural stimulators of NO production. A diet rich in nitrate-containing vegetables, adequate protein for L-arginine supply, and polyphenol-rich foods provides the building blocks. Managing blood pressure, not smoking, and controlling blood sugar all protect the endothelium where NO is produced. Supplements can fill gaps - particularly as you age or if dietary intake is limited - but they cannot compensate for a lifestyle that actively damages the NO production system
- Nitric oxide is a short-lived but critical signalling molecule that regulates blood vessel dilation, blood pressure, exercise performance, and immune function - produced primarily by endothelial cells via the eNOS enzyme.
- Reduced NO bioavailability is one of the earliest detectable markers of cardiovascular disease. When NO signalling is impaired, vessels stiffen, blood pressure rises, and the endothelium becomes vulnerable to damage.
- A 2022 meta-analysis in Frontiers in Nutrition found that beetroot-derived nitrate reduced systolic blood pressure by approximately 5 mmHg in hypertensive patients.
- A 2021 meta-analysis of 118 studies found small but significant endurance performance benefits from nitrate-rich and polyphenol-rich foods, with effects most consistent in males and in recreational rather than highly trained athletes.
- The body uses two NO production pathways: the L-arginine/eNOS pathway (primary, declines with age) and the nitrate-nitrite-NO pathway (dietary backup, requires oral bacteria that antiseptic mouthwash destroys).
- L-citrulline is preferred over L-arginine for supplementation because it bypasses first-pass metabolism and more effectively raises sustained plasma arginine levels, as confirmed by a comprehensive review in the Journal of Strength and Conditioning Research.
- Magnesium is required for proper eNOS function. Deficiency impairs nitric oxide production and is relevant to both cardiovascular and exercise performance goals.
- Nitric oxide is not only an athlete concern. It regulates blood pressure, protects vascular health, and supports brain and organ blood flow for everyone - and NO production declines with age regardless of fitness level.
Common questions
Frequently Asked Questions
Are beets really good for nitric oxide?
Yes, and the evidence is solid. Beetroot is one of the highest dietary sources of inorganic nitrate, which the body converts to nitric oxide through the nitrate-nitrite-NO pathway. A 2022 meta-analysis in Frontiers in Nutrition found beetroot juice lowered systolic blood pressure by around 5 mmHg in hypertensive patients. Endurance performance data also supports beetroot's benefit at recreational exercise intensities. Concentrated beetroot shots or extracts provide a practical way to get a consistent dose.
Is L-citrulline better than L-arginine for nitric oxide support?
In most cases, yes. While L-arginine is the direct precursor to NO, oral L-arginine is heavily metabolised in the gut and liver before it reaches systemic circulation. L-citrulline bypasses this problem - it is absorbed intact and converted to L-arginine in the kidneys, resulting in more sustained plasma arginine levels. A comprehensive review in the Journal of Strength and Conditioning Research confirmed that oral L-citrulline supplementation effectively raises both plasma arginine and total nitrate/nitrite concentrations.
Why does nitric oxide matter for vascular health?
Because it is the primary mechanism by which blood vessels relax and dilate. Without adequate NO, arteries become stiff, blood pressure rises, and the endothelium becomes vulnerable to damage and plaque formation. Endothelial dysfunction, driven largely by reduced NO bioavailability, is now recognised as one of the earliest steps in the development of cardiovascular disease. This is why protecting endothelial function through diet, exercise, and not smoking is so important for long-term vascular health.
Is nitric oxide only important for athletes?
Not at all. While athletes focus on the performance benefits, nitric oxide is critical for everyone. It regulates blood pressure, supports immune function, protects blood vessel health, and maintains healthy blood flow to the brain and organs. NO production declines with age regardless of fitness level, which is why dietary and supplemental support becomes more relevant as you get older - not less.
Can you get enough nitric oxide support from food alone?
For many people, yes - particularly if you regularly eat leafy greens, beetroot, nuts, seeds, and adequate protein. However, the nitrate-nitrite-NO pathway depends on oral bacteria that can be disrupted by antiseptic mouthwash, and the eNOS pathway becomes less efficient with age. If you are over 50, have elevated blood pressure, or eat few nitrate-rich vegetables, supplementation with beetroot extract and/or L-citrulline can meaningfully fill the gap. Regular exercise is also essential - it provides the shear stress that keeps eNOS expression high.
Biosphere Nutrition · New Zealand
Nitric Oxide - L-citrulline, L-arginine, beetroot, vitamin C
Therapeutic doses of eNOS substrates and co-factors to support blood flow, blood pressure, and cardiovascular health. Transparent labelling. Third-party tested.
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Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. If you have high blood pressure, cardiovascular disease, or are taking medication, consult a qualified healthcare professional before starting any supplement or making significant dietary changes. Always read the label and use as directed.