amino acid · for muscle cramps
L-Citrulline
Better blood flow is meant to get oxygen to muscle faster and clear waste sooner.
Say that in clinical terms
Improved blood flow enhances oxygen and nutrient delivery to muscles. Accelerates lactate clearance.
How strong is the research?
1 paper read.
Who was studied: Seven competitive cyclists, and what they were given was whole watermelon juice rather than a citrulline supplement.
PubMed yields zero results when 'citrulline' and 'muscle cramp' are searched together as clinical trial terms. A broader search for 'citrulline cramp' in humans returns 7 papers, none of which test L-citrulline for musculoskeletal cramping; one paper mentions citrulline may relieve GI cramping in a review of athlete GI bleeding, which is a different phenomenon. The systematic reviews on L-citrulline consistently cover post-exercise soreness (DOMS), perceived exertion, and blood lactate — not muscle cramps. The evidence-based review of exercise-associated muscle cramps (PMID 34185846) does not mention citrulline. No human trial or systematic review testing L-citrulline for muscle cramps was f
How much to take
daily
6–8 g
Evidence primarily in exercise-associated muscle cramps.
Before you take it
- No NIH/IOM Tolerable Upper Intake Level (UL) has been established for L-citrulline; long-term safety data at doses above 6 g/day are limited.
- Additive hypotension risk when combined with PDE5 inhibitors (sildenafil, tadalafil, vardenafil); this combination is contraindicated without physician supervision.
- Additive blood pressure-lowering effect when combined with antihypertensive medications (ACE inhibitors, ARBs, calcium channel blockers, beta-blockers, diuretics); medical supervision required before combining.
- L-citrulline is metabolized to L-arginine in the kidneys; caution is advised in individuals with severe renal impairment or known urea cycle disorders.
- No clinical trials have been conducted in pregnant or breastfeeding populations; use during pregnancy or breastfeeding should be avoided without medical guidance.
What we make of it
The study measured muscle soreness, not cramp — and gave people watermelon juice, not citrulline.
The detail
Two things are wrong. It measured delayed soreness after exercise, which is inflammatory; cramps are involuntary contractions usually tied to electrolytes. Those are different conditions. And the seven participants drank watermelon juice rather than taking a supplement, so the dose cannot be treated as equivalent. Seven people is close to no statistical power at all.