What are the safe dosages and considerations for using L-arginine (L-arginine) and citrulline (citrulline) supplements for bodybuilding?

L-Arginine and Citrulline Supplementation for Bodybuilding

For bodybuilding purposes, L-citrulline supplementation (1.2-2.4g/day) appears more effective than L-arginine for enhancing exercise performance, with L-citrulline being more efficient at increasing systemic arginine availability and producing nitric oxide-mediated effects. 1, 2

Mechanism of Action and Benefits

• Both L-arginine and L-citrulline function as precursors to nitric oxide (NO), a potent vasodilator that may enhance blood flow to muscles during exercise 3
• L-citrulline is more efficient than L-arginine at increasing systemic arginine availability because it bypasses first-pass metabolism, with studies showing ~70% of supplemental arginine undergoes first-pass extraction in the splanchnic circulation 1
• L-citrulline can be converted to L-arginine in the body, potentially providing a more sustained increase in plasma arginine levels 4

Dosage Recommendations

• For L-citrulline:

  • Effective dosages range from 1.2-6g daily, with most performance benefits observed at 3-6g daily 2, 5
  • Can be taken as L-citrulline or citrulline malate (which contains malic acid) 4

• For L-arginine:

  • Typical dosages range from 1.2-6g daily, though higher bioavailability is achieved through L-citrulline supplementation 2, 6
  • May be less effective than L-citrulline due to extensive first-pass metabolism 1

Performance Effects

• L-citrulline supplementation has shown more consistent ergogenic benefits than L-arginine, including:

  • Reduced rate of perceived exertion during exercise 6
  • Decreased muscle soreness and improved recovery 2
  • Lower lactate concentrations during high-intensity exercise 6
  • Improved time in maximum exercise tests 6

• Combined supplementation of L-arginine and L-citrulline (1.2g each daily for 7 days) has been shown to:

  • Significantly increase power output during a 10-minute cycling test (242W vs 231W with placebo) 2
  • Improve subjective perceptions of leg muscle soreness and ease of pedaling 2

Safety Considerations

• Both supplements are generally well-tolerated at recommended dosages 5
• Acute supplementation appears safe, though research on long-term use is limited 7
• Training status may influence effectiveness - benefits may be more pronounced in untrained or moderately trained individuals compared to highly-trained athletes 4

Practical Application

• For bodybuilding purposes, L-citrulline appears to be the preferred choice due to superior bioavailability 1
• Timing: Take supplements approximately 60 minutes before exercise for optimal effects 2
• Consider combining both supplements (1.2g each) for potentially synergistic effects on plasma arginine and nitric oxide levels 2
• Effects may vary based on individual response and training status 4

Limitations and Caveats

• Acute supplementation of L-arginine (0.15g/kg) and citrulline malate (0.1g/kg) showed limited benefits across multiple exercise modalities in one recent study 7
• Results are inconsistent across studies, suggesting individual response variability 6, 4
• Most studies have been conducted in male subjects, limiting generalizability to female athletes 2, 7