amino acid · for low stamina
L-Citrulline
Raises the compound that widens blood vessels, getting more oxygen to working muscle.
Say that in clinical terms
Bypasses hepatic metabolism to boost plasma arginine and NO production. Increases blood flow and oxygen delivery.
How strong is the research?
In 28 recreationally active men, it gave no benefit for endurance exercise.
2 papers read, 1 supporting, 1 against.
Tested as: Citrulline malate (8 g)
Who was studied: 41 men doing weight training. Endurance and mixed-sex groups were not tested.
The research we could find tested Citrulline malate (8 g). That is a different preparation, and a result for one form is not a result for another.
How much to take
daily
6–8 g
L-citrulline malate (2:1 ratio) most studied. Take 60-90 minutes pre-exercise.
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 trial used citrulline malate, which is roughly half malic acid — and malate does things of its own.
The detail
The study gave 8 g of citrulline malate, not citrulline. Only about 57% of that is citrulline by weight, and the malic acid half has effects of its own on energy metabolism, so the result cannot be credited to citrulline.