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Moderate evidencePhysical performance

Nitric Oxide Boosters

Two nitric oxide precursors have real evidence — dietary nitrate (beetroot) and L-citrulline — while L-arginine, the ingredient most "NO booster" labels lead with, is largely destroyed by first-pass metabolism and performs poorly. Buy the ingredient, not the blend.

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What the science says

  • Dietary nitrate improves muscle power and short high-intensity efforts Strong evidence

    An individual-participant-data meta-analysis of dietary nitrate found a significant increase in maximal knee-extensor power (about 5%), with the largest effects at high contraction velocities. Meta-analyses of high-intensity and repeated-sprint work show small but consistent benefits at 6-13 mmol (roughly 400-800 mg) nitrate taken 2-3 hours before exercise.

  • L-citrulline raises plasma arginine better than arginine itself does Moderate evidence

    Citrulline escapes intestinal and hepatic arginase, so oral citrulline raises plasma arginine more effectively than an equivalent dose of arginine. Meta-analyses of citrulline supplementation show small improvements in aerobic performance outcomes and time-to-exhaustion at 6-8 g citrulline malate, though effects on strength and repetitions are inconsistent.

  • L-arginine, the classic NO ingredient, mostly does not work Limited evidence

    Oral arginine undergoes extensive first-pass degradation by intestinal and hepatic arginase, so typical 3-6 g label doses produce little sustained rise in NO metabolites. Performance trials are largely null, and doses high enough to matter (>10 g) commonly cause diarrhoea.

  • "Pump" is not the same as performance Limited evidence

    The visible vasodilation these products are sold on reflects acute blood flow and often glycerol- or salt-driven cell hydration, not strength or hypertrophy. No trial has shown that acute pump magnitude predicts long-term muscle growth.

Dosage & safety

Studied doseNitrate: 6-13 mmol (about 400-800 mg) as beetroot juice or concentrate, 2-3 h pre-exercise; chronic dosing for 3-15 days may add benefit. L-citrulline: 3-6 g pure, or 6-8 g citrulline malate, roughly 60 min pre-exercise. Typical blend labels: 1-2 g arginine AKG, 500 mg-1 g citrulline, 250-500 mg beetroot extract of unstated nitrate content — all far below studied doses. Agmatine, arginine nitrate and "nitrosigine" have thin independent evidence.
SafetyNitrate turns urine and stools pink or red (harmless) and can cause GI upset; antibacterial mouthwash blunts its effect by killing the oral bacteria that reduce nitrate to nitrite. High-dose citrulline and arginine cause diarrhoea and abdominal discomfort. Anyone taking nitrates for angina, PDE5 inhibitors (sildenafil, tadalafil), or antihypertensives should be cautious about additive blood-pressure lowering. Beetroot is high in oxalate, a consideration for calcium-oxalate stone formers. NO blends sometimes also contain yohimbine or synephrine — check the full label.

How to take it

TimingBeetroot nitrate 2-3 hours before exercise; citrulline about 60 minutes before.
With food?Either way.
Worth knowingBlend labels rarely state nitrate content — buy beetroot products that declare millimoles of nitrate, and buy citrulline as a standalone powder.

Interactions

With medications

  • nitrate medication for angina (isosorbide, nitroglycerin)

    Both work through the same nitric oxide pathway and blood pressure can drop too far. do not combine without medical supervision

  • PDE5 inhibitors (sildenafil, tadalafil)

    Additive vasodilation can cause symptomatic hypotension. do not combine without medical supervision

  • blood-pressure medication

    Dietary nitrate and citrulline lower blood pressure on their own. monitor your blood pressure when you start

  • antibacterial (chlorhexidine) mouthwash

    It kills the oral bacteria that reduce dietary nitrate to nitrite, abolishing most of beetroot's effect. skip mouthwash on the days you use nitrate

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Do nitric oxide boosters improve workout performance?

Two nitric oxide precursors have real evidence: dietary nitrate from beetroot (strong evidence for small gains in power and high-intensity efforts) and L-citrulline (moderate evidence for small aerobic benefits). Most NO booster blends, however, contain these at far below studied doses, so buying the single ingredient makes more sense than buying the blend.

Does L-arginine boost nitric oxide?

L-arginine, the ingredient most NO booster labels lead with, mostly does not work: it is largely broken down by first-pass metabolism, so typical 3-6 g doses produce little sustained rise in nitric oxide metabolites (limited evidence). Doses high enough to matter (over 10 g) commonly cause diarrhoea; L-citrulline raises plasma arginine more effectively.

How much beetroot nitrate or citrulline should I take before exercise?

For a nitric oxide boost, the studied nitrate dose is 6-13 mmol (about 400-800 mg) as beetroot juice or concentrate, 2-3 hours before exercise. For L-citrulline, studied doses are 3-6 g pure or 6-8 g citrulline malate about 60 minutes before exercise.

Can I take a nitric oxide booster with Viagra or blood pressure pills?

Nitric oxide boosters should not be combined with PDE5 inhibitors (sildenafil, tadalafil) or angina nitrates without medical supervision, because the additive vasodilation can drop blood pressure too far. If you take blood-pressure medication, monitor your blood pressure when you start, since dietary nitrate and citrulline lower it on their own.

Scientific references

Where to buy

Nutricost, Performance, Nitric Oxide Booster, 180 Capsules

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