Supplement analysis backed by scientific evidence · PT

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Moderate evidencePhysical performance

L-Citrulline

Citrulline bypasses the gut-and-liver breakdown that cripples oral arginine, making it the more effective nitric oxide precursor. Meta-analyses show a small but real increase in resistance-training repetitions and reduced post-exercise soreness — modest, but among the better-supported pre-workout ingredients.

What the science says

  • Increasing resistance-training volume Moderate evidence

    Vårvik's 2021 systematic review and meta-analysis found acute citrulline malate increased total repetitions performed during resistance training versus placebo, though the pooled effect was small (roughly one to two extra reps across multiple sets). Effects were more consistent for upper-body, multiple-set-to-failure protocols.

  • Reducing post-exercise muscle soreness Moderate evidence

    Rhim's 2020 meta-analysis found citrulline supplementation significantly reduced muscle soreness at 24 and 48 hours post-exercise, and reduced rating of perceived exertion, while having no significant effect on blood lactate. The soreness effect is consistent across trials but modest in size.

  • Lowering blood pressure and improving vascular function Moderate evidence

    Citrulline raises plasma arginine and nitric oxide availability more effectively than equivalent doses of arginine, and randomised trials report small reductions in blood pressure and improvements in endothelial function, particularly in older or hypertensive adults. Note that one widely cited citrulline blood-pressure meta-analysis was retracted, so treat the pooled numbers with caution.

  • Endurance performance Limited evidence

    Endurance trials are mixed, with many null results for time-trial and time-to-exhaustion outcomes. Any benefit appears smaller and less reliable than the resistance-training effect.

Dosage & safety

Studied dose6-8 g of citrulline malate (roughly 3.5-4.5 g pure L-citrulline) taken 60 minutes pre-exercise is the standard acute performance protocol. Cardiovascular trials use 3-6 g/day of pure L-citrulline for 2-8 weeks. Note that citrulline malate is typically a 2:1 blend, so a "6 g" label supplies about 4 g of actual citrulline — and some published effects may partly reflect the malate.
SafetyVery well tolerated; unlike arginine, doses up to 15 g rarely cause GI distress. Blood-pressure-lowering effect can be additive with antihypertensives, nitrates and PDE5 inhibitors such as sildenafil — do not combine without medical advice. Insufficient data in pregnancy and breastfeeding. Not prohibited by WADA. Caution in people with kidney disease given increased nitrogen handling.

Scientific references

Where to buy

Nutricost, L-Citrulline Malate 2:1, Unflavored, 21.4 oz (600 g)

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