UK Buyer's Guide · Updated 2026

Nitric oxide supplements: the actual science, not the hype.

If you're researching NO supplements you're already past the surface. You want to understand the mechanism, compare the precursor pathways properly, and pick a supplement that targets what the published research actually supports. This guide goes deep: the 1998 Nobel Prize that established the field, the three precursor routes compared in clinical detail, the mouthwash gotcha most retailers don't mention, and how to actually tell if a supplement is working.

Written by the Matter team. Reviewed by Dr Syed Nouman Kazmi, MBBS, FCPS, Consultant Cardiologist.

Hands at a kitchen counter with the Daily Beets pouch and capsules Cardiologist reviewed

Hi, my name is Max, one of the co-founders here at Matter. If you've already heard about nitric oxide, you're a step ahead of most people. The problem: a lot of supplements on the market use weak, underdosed formulas that don't actually deliver. I built Daily Beets to do this properly, with research-aligned doses on the dietary nitrate pathway specifically. I hope this page explains the science behind that choice.

1998

Nobel Prize for NO research

3

Precursor pathways

7,500mg

Beetroot equivalent per serving

90 days

Money-back guarantee

Where the science started

The 1998 Nobel Prize that created this category.

If you've ever wondered why "nitric oxide" suddenly became a buzzword in the supplement aisle, the answer is a single piece of medical research from the late 1980s and 1990s.

1980

Robert Furchgott, a pharmacologist at Brooklyn's SUNY Downstate, discovered that the inner lining of blood vessels (the endothelium) released a chemical that caused the vessels to relax. He called it "endothelium-derived relaxing factor" (EDRF). Nobody knew what it was.

1986

Louis Ignarro at UCLA and Salvador Moncada in London independently identified the EDRF as nitric oxide: a tiny gas molecule. Until that point, NO was best known as a toxic atmospheric pollutant. The idea that the body manufactured it as a signalling molecule was completely new.

1988

Ferid Murad showed that nitroglycerin (used since the 1860s for angina, but with no understood mechanism) worked by releasing nitric oxide. This connected NO to cardiovascular medicine for the first time.

1998

Furchgott, Ignarro, and Murad shared the Nobel Prize in Medicine[1] "for their discoveries concerning nitric oxide as a signalling molecule in the cardiovascular system." The supplement industry has been catching up ever since.

2008+

The Bryan Lab at the University of Texas pioneered the dietary nitrate pathway[2], showing that beetroot juice could meaningfully lower blood pressure within hours. This is the research base that the most evidence-strong NO supplements are built on today.

What NO does in your body

It tells your blood vessels to relax.

Nitric oxide (NO, not nitrous oxide) is a small gas molecule produced by the cells lining your blood vessels. When the endothelium releases NO, it signals the smooth muscle of the vessel walls to relax. The vessel widens (vasodilation). Blood flows more easily. Pressure on the system drops.

This isn't an esoteric mechanism. It's how nitroglycerin (GTN) has worked for angina patients since the 1860s. NO is one of the most fundamental signalling molecules in cardiovascular health, and the published research on supporting NO production is some of the strongest in the natural-supplement space.

Microscopy view of branching red capillary network
Why this matters more with age

Your body's NO production declines as you age.

Endothelial NO synthase (eNOS, the enzyme that produces NO in your blood vessels) becomes less efficient with age[3]. The decline is steady, measurable, and cumulative. Approximate values from published research:

Age 20
100%
Age 40
~75%
Age 50
~65%
Age 60
~50%
Age 70
~38%

Indicative values from published research. Individual decline rates vary based on genetics, lifestyle, smoking status, and existing cardiovascular health. The pattern is consistent across populations: NO production drops steadily after age 40.

What the shelf is actually selling

You can't put nitric oxide in a capsule.

Nitric oxide is a gas your body makes on demand and spends within seconds. Nothing on sale in the UK contains it, and nothing can. What you're buying is a precursor: a raw material your body may turn into nitric oxide, assuming the route you're feeding still works.

The honest case against most of this shelf

There's a reasonable argument that nobody should buy a nitric oxide supplement at all, and it deserves a straight answer rather than a counter-pitch. It runs like this: you can't bottle the gas, and the amino-acid products that dominate the shelf ask your body to do a job it's getting worse at with every decade.

On the second half, the pathway comparison further down this page agrees. L-arginine rates weakest of the three for cardiovascular outcomes, because most of an oral dose is broken down in the gut wall and liver long before it reaches a blood vessel[7]. So we'll say the unhelpful-to-us part out loud. If what you're holding is a tub of L-arginine, that argument is right and you should keep your money.

Where the argument stops working

It leans on one phrase doing two jobs. "Nitric oxide supplement" covers two different routes into the same molecule, and they don't share an evidence base. The amino-acid route asks an enzyme to work harder, and that enzyme is the one that gets less efficient as you age[3]. The dietary nitrate route goes around it: nitrate concentrates in your saliva, bacteria on your tongue reduce it to nitrite, and your stomach does the final conversion.[2]

So "you can't supplement nitric oxide" is true and beside the point. You can't buy the gas. You can feed the pathway that makes it, and one of those pathways has published cardiovascular trial data behind it while the other has a mechanism and a marketing budget. If it's the beetroot end of this you're weighing up, our UK beetroot supplement guide compares the actual products.

The three precursor routes

How NO supplements actually work.

Your body doesn't store nitric oxide; it builds it on demand from precursors. Three pathways exist. The evidence base for each is genuinely different. This is the section that separates a thoughtful supplement choice from a marketing-driven one.

1

Dietary nitrate pathway

NO3⁻ → NO2⁻ → NO (via oral microbiome)
Strongest evidence

How it works

Dietary nitrates (from beetroot, leafy greens, certain root vegetables) are absorbed and concentrate in saliva. Specific oral bacteria reduce nitrate (NO3⁻) to nitrite (NO2⁻). Once swallowed, the acidic stomach environment converts nitrite into nitric oxide. This route bypasses the eNOS enzyme entirely, useful in older adults whose eNOS is declining.

What the research shows

Around 30 published clinical trials show acute (single-dose) blood pressure reductions of 4-5 mmHg systolic from beetroot juice[4,5] or extract, with sustained effects from daily dosing over 4-8 weeks. The Bryan Lab research at UT and the Wylie group in the UK have built the modern evidence base.

Best food source

Beetroot (highest density of dietary nitrate per serving). Spinach, rocket, swiss chard, and celery are also good sources but require larger volumes.

Best supplement form

Standardised beetroot extract (50:1 or higher) at the equivalent of 5,000-10,000mg powder per serving. Beetroot juice works but adds 20g+ sugar per glass.

2

L-citrulline pathway

L-citrulline → L-arginine → NO (via eNOS)
Moderate evidence

How it works

L-citrulline (an amino acid) is absorbed efficiently from the gut, converted to L-arginine in the kidneys, then used by the eNOS enzyme to produce NO. This indirect route is more efficient than supplementing L-arginine directly because L-citrulline isn't broken down in the gut wall the way arginine is.

What the research shows

Published trials show modest blood pressure reductions (3-5 mmHg systolic) from L-citrulline supplementation at 3-6g daily over 6-8 weeks. Stronger evidence for athletic recovery and exercise endurance than for cardiovascular outcomes specifically.

Caveat

L-citrulline depends on functional eNOS to convert L-arginine into NO. In older adults whose eNOS is declining, this pathway becomes less efficient, which is partly why dietary nitrates (pathway 1) tend to outperform L-citrulline in older populations.

Best supplement form

L-citrulline malate or L-citrulline base, 3-6g per serving. Doses below 3g typically don't reach research thresholds.

3

L-arginine pathway

L-arginine → NO (via eNOS)
Weakest evidence

How it works

L-arginine is the direct substrate that eNOS converts to NO. In theory, supplementing L-arginine should boost NO production directly. In practice, oral L-arginine has poor bioavailability. Much of it is metabolised in the gut wall and liver before it reaches systemic circulation.

What the research shows

Mixed. Some trials show modest cardiovascular effects, others show none. Recent meta-analyses are not enthusiastic. Effective oral doses are large (6-10g daily) and tolerability can be an issue.[7] L-arginine remains popular in pre-workout supplements but the cardiovascular case is weaker than for the other two pathways.

Caveat

The 2006 VINTAGE MI trial found L-arginine supplementation post-heart-attack increased mortality. This is one specific population (recent MI), but it underscores that "more substrate = more NO" isn't reliably true and the supplement isn't risk-free.

If you've already bought it

Not harmful at moderate doses for general use, but if you're choosing today, L-citrulline or dietary nitrates are better-evidenced choices.

For cardiovascular outcomes specifically (blood pressure, vascular function, endothelial health), pathway 1 (dietary nitrates) has the most robust evidence base. Daily Beets is built on this pathway, with hibiscus and grape seed adding complementary vascular support.

The thing nobody mentions

Antiseptic mouthwash kills your nitrate-to-NO conversion.

Pathway 1 (dietary nitrates) depends on specific bacteria living on your tongue and in the back of your mouth. These bacteria reduce nitrate (NO3⁻) to nitrite (NO2⁻), which then converts to NO in the stomach. They're a small but critical part of the chain.

Antiseptic mouthwashes (Listerine, chlorhexidine, anything advertising "kills 99.9% of bacteria") wipe these bacteria out for hours. Multiple studies have shown that using antiseptic mouthwash blocks or significantly blunts the BP-lowering effect of dietary nitrates.[6] One UK study found systolic BP rose by ~3 mmHg in healthy adults after 7 days of twice-daily Listerine use.

If you're taking beetroot or any dietary nitrate supplement for cardiovascular benefit: avoid antiseptic mouthwash entirely, or at minimum avoid it for 30+ minutes after taking the supplement. Standard fluoride toothpaste is fine; that's not the issue. It's specifically antiseptic rinses that kill the nitrate-reducing bacteria.

NO supplements aren't all the same goal

Three different reasons people take NO supplements.

The same molecule supports different outcomes. The right precursor pathway depends on what you're actually trying to do.

Use case 1

Cardiovascular health

Blood pressure support, endothelial function, healthy circulation. The classic use case for older adults whose NO production is declining with age.

Best pathway: Dietary nitrates (beetroot). Strongest published BP evidence and bypasses the declining eNOS enzyme.
Use case 2

Athletic / recovery

Exercise endurance, recovery between sessions, blood-flow-driven performance. Common in cyclists, runners, lifters in their 30s and 40s.

Best pathway: L-citrulline (3-6g pre-workout) for short-term performance. Beetroot juice has good acute exercise data too.
Use case 3

Erectile / sexual function

NO is central to erectile mechanism (this is why Viagra works because it amplifies the NO pathway). Some men explore NO supplements as an alternative or adjunct.

Honest read: Modest effect from L-citrulline (1.5-3g) in mild ED. Not equivalent to PDE5 inhibitors. Talk to your GP if ED is persistent. It's often a cardiovascular warning sign worth investigating.

Daily Beets is built for use case 1 (cardiovascular). It's not optimised as a pre-workout (no L-citrulline) or as an ED-specific product. If your goal is athletic performance, an L-citrulline product is a better fit. If your goal is BP and circulation support, the multi-pathway nitrate route is the strongest evidence-based option.

Who the shelf was designed for

Most of this category is built for people half your age.

Walk the supplement aisle and the nitric oxide shelf is a pre-workout shelf: tubs, scoops, pump claims, somebody mid-deadlift on the label. There's no conspiracy in that. The sports market got here first and the formulations still answer its question, which is how to move more blood through a muscle during forty minutes of effort.

THE DIFFERENT QUESTION

At 60 you're not asking about the forty minutes

You're asking what your blood vessels are doing for the other twenty-three hours. That's a different brief, and it changes which pathway is worth paying for. The enzyme that makes nitric oxide in your vessel walls gets less efficient as you age[3], and that enzyme is exactly what a citrulline or arginine product leans on. The nitrate route doesn't need that enzyme, which is why the cardiovascular research keeps landing there[2] and the pre-workout research doesn't.

Same molecule, same aisle, two unrelated buying decisions. Our explainer on what nitric oxide actually does covers the biology at more length.

Decision 1

Start with the pathway

If the goal is circulation support rather than a better set in the gym, the dietary nitrate route is the one with the cardiovascular trial evidence. Check which pathway is on the label before you compare prices.

Decision 2

It goes in the morning routine

Pre-workout formats are timed around training. A vascular-health routine is timed around nothing: it's the same two capsules every morning, and consistency over weeks matters more than any single dose.

Decision 3

You'll have to measure this one

Pump is something you can feel in minutes. Vascular support isn't. Take a baseline week of morning and evening readings before you start anything, then keep taking them. The section below sets out how.

Daily Beets is built for the twenty-three hours rather than the forty minutes. It supports healthy blood pressure and healthy circulation, taken daily, and it's a food supplement, not a medicine. If your goal is athletic performance, an L-citrulline product is the better buy.

Practical biomarkers

How to actually tell if your NO supplement is doing something.

Subjective "I feel better" is unreliable. Here's what to actually measure or notice.

Things you can track at home

Resting blood pressure (the gold standard). Take morning + evening readings for a baseline week before starting, then weekly during the supplement protocol. A 4-8 mmHg systolic reduction over 6-8 weeks is the expected effect size for dietary nitrates. Use Matter's free BP Tracker or any home BP monitor.

Cold hands and feet (peripheral circulation). Anecdotal but commonly reported. People with reduced NO often have cold extremities; improvement over weeks of dietary nitrate supplementation suggests vasodilation is working.

Exercise recovery time. If you exercise regularly, time how long it takes for your heart rate to drop to resting after moderate effort. Improvement over weeks suggests vascular function is improving.

Beeturia (urine going pink). Not a measure of effectiveness, but a useful signal that the betalain pigments from beetroot are passing through your system. Around 10-15% of people get noticeable beeturia. Harmless.

Salivary nitrate test strips. Available online (Berkeley Test, HumanN). Measure salivary nitrate as a proxy for NO production capacity. Useful for confirming the dietary nitrate pathway is active. Not a perfect measurement but more direct than feel.

Where Daily Beets fits

Built on the strongest pathway, with complementary support.

Matter is a UK cardiovascular health brand. Daily Beets is our 12-ingredient capsule formula built specifically for use case 1 above (cardiovascular health), using the dietary nitrate pathway as the primary mechanism.

The active stack: 150mg of standardised 50:1 beetroot extract (equivalent to 7,500mg of beetroot powder, sufficient for the nitrate pathway), 700mg of 5:1 hibiscus extract (independent vascular tone support), 200mg of grape seed extract (polyphenol vascular function), and a complete B-vitamin complex (B1, B6, B9, B12) for homocysteine metabolism. Plus seven supporting botanicals.

It does NOT contain L-arginine or L-citrulline. We've left those out because the dietary nitrate pathway has stronger published cardiovascular evidence in the 45-75 age range, and because cramming everything into one capsule means none of it hits a meaningful dose. If you're optimising for athletic performance specifically, an L-citrulline product is a better fit. For cardiovascular support, dietary nitrates plus hibiscus is the most robust play.

90-day money-back guarantee. Cardiovascular response is individual; if it doesn't help in 90 days, you don't pay for it.

Top-down editorial flatlay of Daily Beets ingredients
Reviewed by Dr Syed Nouman Kazmi, MBBS, FCPS

Consultant Cardiologist. Reviews Matter's Heart Health Resource Centre and product information for clinical accuracy and safety, including the pathway analysis above.

Pathway-specific questions

What science-curious UK customers actually ask.

Why doesn't Daily Beets contain L-arginine or L-citrulline?
Three reasons. First, the dietary nitrate pathway has stronger published cardiovascular evidence than L-arginine or L-citrulline for the 45-75 age range. Second, L-arginine has poor oral bioavailability and the post-MI safety signal from the VINTAGE MI trial gives us pause. Third, L-citrulline at meaningful doses (3-6g) is bulky enough that cramming it into a multi-pathway formula means everything else gets crowded out. We chose to do one pathway well rather than several pathways at sub-clinical doses.
Is L-arginine actually dangerous?
Not at general supplement doses for healthy adults. The 2006 VINTAGE MI trial found L-arginine supplementation post-heart-attack increased mortality vs placebo[8], but that's one specific high-risk population. For general use, L-arginine at typical supplement doses appears safe. The bigger issue is that effectiveness for cardiovascular outcomes is weak, so you're not gaining much. If you have a recent MI history, talk to your cardiologist before any L-arginine or NO-targeting supplement.
How quickly does the dietary nitrate pathway actually work?
Acutely fast. Plasma nitrate peaks within 1-2 hours of a beetroot dose; nitrite peaks 2-3 hours after that; measurable BP reduction is typically detectable within 4-6 hours of a single dose. Sustained cardiovascular effects accumulate over 4-8 weeks of consistent daily dosing. The mechanism is real; the question is just whether the dose is large enough and whether you're consistently taking it.
What's the deal with mouthwash, really?
Specific oral bacteria (in the dorsal posterior tongue, mostly) reduce dietary nitrate to nitrite as the first step in the nitrate-to-NO conversion. Antiseptic mouthwashes (Listerine, chlorhexidine) wipe these bacteria out for hours. Multiple controlled studies show this measurably blunts the BP-lowering effect of dietary nitrates. Standard fluoride toothpaste is fine. The issue is specifically antiseptic rinses. If you take beetroot for cardiovascular benefit, skip the antiseptic mouthwash, or use it only well away from your supplement timing.
Can I just eat more beetroot instead?
Yes, in principle. Around 250-500ml of beetroot juice daily (or ~200g of cooked beetroot) provides similar nitrate to a typical Daily Beets serving. The trade-offs are sugar (juice has ~20g per 250ml glass), convenience (you're committing to a daily juice ritual), and the fact that pure beetroot is single-pathway. The supplement route lets you stack hibiscus, grape seed, and B vitamins in the same daily dose, which the juice alone doesn't.
Does NO supplementation interact with Viagra or similar?
PDE5 inhibitors (Viagra, Cialis, Levitra) work by amplifying the NO pathway. Combining them with NO-boosting supplements is generally considered safe for healthy adults but the combined effect on blood pressure can be larger than expected. The bigger interaction warning is with prescription nitrates (GTN, isosorbide mononitrate for angina). Combining those with NO supplements can cause significant hypotension. Talk to your GP if you're on any of these.
What about L-citrulline malate vs L-citrulline base?
Citrulline malate is L-citrulline bound to malic acid, originally developed as a fatigue treatment in France. It's the form most studied for athletic performance. L-citrulline base is just the amino acid alone. Both convert to L-arginine and then NO via the same pathway. For cardiovascular outcomes the difference is marginal; for exercise performance some athletes report citrulline malate feels different. Not a major decision either way.
How do I see Daily Beets's full ingredient breakdown?
Full label, dosages, and current pricing on the Daily Beets product page. Two-capsule serving, 60 capsules per bag, 30-day supply, UK-formulated, 90-day money-back guarantee.
What is a nitric oxide supplement?
A supplement that gives your body the raw material to make nitric oxide, rather than the molecule itself. Nitric oxide is a gas your body builds on demand and uses within seconds, so no capsule, tub or drink contains it. Products in this category supply a precursor by one of two broad routes: dietary nitrate, usually from beetroot, or an amino acid such as L-arginine or L-citrulline. The route matters more than the brand, because the published evidence behind the two isn't comparable.
Do nitric oxide supplements work?
It depends on which pathway you bought, and at what dose. The dietary nitrate route has the strongest published cardiovascular evidence of the three: controlled trials measuring blood pressure after a nitrate load[4], and a meta-analysis pooling them[5]. L-citrulline has reasonable short-term exercise data. L-arginine is the weakest of the three for cardiovascular outcomes, mostly because very little of an oral dose survives first-pass metabolism[7]. "Do nitric oxide supplements work" isn't a question with one answer, however often it gets sold as one.
Is beetroot the same as a nitric oxide supplement?
Beetroot is one kind of nitric oxide supplement, and the kind with the clearest cardiovascular research behind it. It works through dietary nitrate: oral bacteria convert nitrate to nitrite, and the body converts nitrite to nitric oxide. That route bypasses the enzyme the amino-acid products rely on, which is the reason it keeps appearing in trials involving older adults. So a beetroot supplement is always a nitric oxide supplement. A product marked "nitric oxide" might contain no nitrate at all.
Does nitric oxide production really decline with age?
Yes, and it's one of the better-documented parts of this field. The enzyme that produces nitric oxide in your blood vessel walls becomes less efficient over time[3], and the decline is steady rather than a cliff edge. The figures in the chart above are indicative rather than a personal forecast: individual rates vary with genetics, smoking status, activity and existing cardiovascular health. Which is why the pathway that leans least on that enzyme is the one that holds up best as you get older.
Daily Beets supplement pouch on warm brown surface
If pathway 1 fits your goal

Try the dietary nitrate route. For 90 days.

Two capsules a morning. The strongest-evidence NO precursor pathway, paired with hibiscus and grape seed for vascular support beyond NO alone. If you don't feel a genuine difference within 90 days, you pay nothing.

Try Daily Beets
Further reading

Related guides from ourHeart Health Resource Centre.

Free, in-depth articles on the same topics. No sign-up required.

NO supplements

Nitric oxide supplements: what you need to know

Read article →
NO mechanism

Nitric oxide explained: a simple guide to circulation and vascular health

Read article →
NO function

What does nitric oxide do for you?

Read article →
Drink choices

What's the best drink for blood circulation?

Read article →
Sources

Referencescited above.

All claims about clinical effect sizes and pathway mechanisms reference published research. Citations link to PubMed searches or the source publication directly.

  1. The Nobel Prize in Physiology or Medicine 1998. Awarded jointly to Robert F. Furchgott, Louis J. Ignarro and Ferid Murad "for their discoveries concerning nitric oxide as a signalling molecule in the cardiovascular system." nobelprize.org
  2. Lundberg JO, Weitzberg E, Gladwin MT. The nitrate-nitrite-nitric oxide pathway in physiology and therapeutics. Nature Reviews Drug Discovery. 2008;7(2):156-167. The canonical review of the dietary nitrate route. PubMed
  3. Toda N, Toda H. Nitric oxide-mediated blood flow regulation as affected by smoking and nicotine. European Journal of Pharmacology. 2010;649(1-3):1-13. Reviews age-related decline in eNOS function. PubMed
  4. Webb AJ, Patel N, Loukogeorgakis S, et al. Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite. Hypertension. 2008;51(3):784-790. PubMed
  5. Siervo M, Lara J, Ogbonmwan I, Mathers JC. Inorganic nitrate and beetroot juice supplementation reduces blood pressure in adults: a systematic review and meta-analysis. Journal of Nutrition. 2013;143(6):818-826. PubMed
  6. Govoni M, Jansson EÅ, Weitzberg E, Lundberg JO. The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash. Nitric Oxide. 2008;19(4):333-337. The original mouthwash + nitrate study. PubMed
  7. Schwedhelm E, Maas R, Freese R, et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. British Journal of Clinical Pharmacology. 2008;65(1):51-59. PubMed
  8. Schulman SP, Becker LC, Kass DA, et al. L-arginine therapy in acute myocardial infarction: the Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial. JAMA. 2006;295(1):58-64. The post-MI safety signal. PubMed