Supplement analysis backed by scientific evidence · PT

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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.

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.

Scientific references

Where to buy

Nutricost, Performance, Nitric Oxide Booster, 180 Capsules

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