Amino Acid
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L-Arginine boosts nitric oxide production, supporting blood flow and cardiovascular health. Meta-analyses show 3-6 g/day can lower blood pressure by 5-7 mmHg systolic. However, L-Citrulline may be more effective at sustaining elevated plasma arginine due to better oral bioavailability.
L-Arginine has solid evidence for blood pressure reduction (meta-analysis: -5.4 mmHg systolic) and emerging evidence for erectile dysfunction. However, its bioavailability is limited by extensive first-pass metabolism via arginase in the gut and liver. L-Citrulline bypasses this metabolism and may be more effective at sustaining elevated arginine and NO levels. Arginine remains useful for wound healing and as part of cardiovascular support protocols.
L-Arginine has solid evidence for blood pressure reduction (meta-analysis: -5.4 mmHg systolic) and emerging evidence for erectile dysfunction.
| Form | Bioavailability | Best For |
|---|---|---|
| L-Arginine HCl | Moderate | General supplementation; most common and affordable form |
| L-Arginine Alpha-Ketoglutarate (AAKG) | Moderate | Pre-workout and exercise performance applications |
| Sustained-Release L-Arginine | Moderate-High | Cardiovascular support with steadier plasma levels |
General recommendation: 3-6 g daily, divided into 2-3 doses
Timing: Divided doses 2-3 times daily on an empty stomach; pre-workout for exercise
| Condition | Recommended Dose | Evidence |
|---|---|---|
| Blood pressure support | 4-6 g daily in divided doses | Moderate |
| Erectile dysfunction | 3-5 g daily | Moderate |
| Exercise performance | 3-6 g 30-60 min pre-workout | Moderate |
| Wound healing | 4.5-9 g daily | Moderate |
Upper limit: Up to 20 g/day used in clinical studies; GI side effects common above 10 g/day
Safety profile: Safe with Caution
L-Citrulline is generally more effective at raising plasma arginine levels because it bypasses first-pass metabolism in the gut and liver. A study by Schwedhelm et al. (2008) showed oral citrulline increased plasma arginine more effectively than arginine itself. For sustained NO production, citrulline is preferred; arginine may still be useful for acute dosing.
Yes, moderately. A 2019 meta-analysis of 10 RCTs found L-arginine (1.5-5 g/day) significantly improved erectile function scores. It works by increasing NO, which is essential for penile blood flow. Combining arginine with Pycnogenol (pine bark extract) showed enhanced effects in the Prelox study. It is less potent than PDE5 inhibitors but may help mild cases.
Yes. A meta-analysis of 11 RCTs showed L-arginine at 4-24 g/day reduced systolic blood pressure by an average of 5.4 mmHg and diastolic by 2.7 mmHg. Effects are most pronounced in those with elevated blood pressure. If you take antihypertensive medications, consult your doctor as effects may be additive.