The combined effect of L-arginine and Vitamin C supplementation on nitrogen balance, body composition, maximal oxygen uptake, and anabolic-catabolic hormones in male bodybuilders: A randomized double-blind clinical trial.
Supplementation with L-arginine and Vitamin C may improve VO₂max and testosterone levels in male bodybuilders, but the clinical relevance of these findings is uncertain due to limitations in the study design.
Where it sits
this study against the rest of the vasopressin corpusSummary and findings
This study measured the effects of combined L-arginine (3000 mg/day) and Vitamin C (500 mg/day) supplementation on nitrogen balance, body composition, maximal oxygen uptake (VO₂max), and anabolic-catabolic hormones in 50 male bodybuilders over 45 days. The intervention group showed significant increases in VO₂max and serum testosterone levels, alongside reductions in body weight, BMI, and body fat compared to the placebo group. No significant changes were observed in serum levels of growth hormone or cortisol.
Abstract
<h4>Purpose</h4>This study aimed to investigate the effects of combined L-arginine and Vitamin C supplementation on nitrogen balance, body composition, maximal oxygen consumption (VO₂max), and serum levels of growth hormone (GH), testosterone, cortisol, glucose and lipid profile in male bodybuilding athletes.<h4>Methods</h4>In a randomized, double-blind, placebo-controlled trial, 50 male bodybuilders (mean age: 24.19 ± 3.83 years) were allocated to either an intervention group (<i>n</i> = 25) receiving 3000 mg/day L-arginine (3 × 1000 mg) plus 500 mg/day Vitamin C, or a placebo group (<i>n</i> = 25) receiving starch, for 45 days. All participants followed a standardized combined resistance and aerobic exercise protocol. Anthropometric measurements, biochemical markers, and VO₂max were assessed pre- and post-intervention.<h4>Results</h4>Compared to the placebo group, the supplement group demonstrated a significant increase in VO₂max (<i>p</i> < 0.001) and serum testosterone levels (<i>p</i> < 0.001). A significant reduction was observed in body weight (<i>p</i> < 0.001), BMI (<i>p</i> = 0.004), and body fat (<i>p</i> < 0.001) in the intervention group. However, no significant changes were found in serum levels of GH or cortisol between the groups (<i>p</i> > 0.05). While urinary urea nitrogen decreased significantly, the change in nitrogen balance did not reach statistical significance between groups after adjusting for confounders.<h4>Conclusion</h4>Supplementation with L-arginine and Vitamin C, in conjunction with a structured training program, can improve athletic performance (VO₂max), enhance anabolic status (increased testosterone), and favorably alter body composition by reducing fat mass in male bodybuilders, without significantly affecting GH or cortisol levels.
Background
This study addresses the impact of L-arginine and Vitamin C supplementation on athletic performance and body composition in male bodybuilders, a topic of interest given the popularity of these supplements in sports nutrition. Previous research has suggested potential benefits of these compounds, but evidence remains inconclusive regarding their combined effects in this specific population. Understanding these effects can help inform dietary strategies for athletes aiming to enhance performance and body composition.
Methods
This was a randomized, double-blind, placebo-controlled trial involving 50 male bodybuilders with a mean age of 24.19 ± 3.83 years. Participants were divided into an intervention group (n=25) receiving 3000 mg/day L-arginine plus 500 mg/day Vitamin C, and a placebo group (n=25) receiving starch, for a duration of 45 days. Primary outcomes included VO₂max, body composition metrics, and serum hormone levels, assessed pre- and post-intervention.
Results
The primary endpoint showed a significant increase in VO₂max in the supplement group compared to placebo, with a p-value of <0.001. Additionally, serum testosterone levels increased significantly (p<0.001), while reductions in body weight (p<0.001), BMI (p=0.004), and body fat (p<0.001) were also noted. However, no significant changes were found in serum levels of growth hormone or cortisol (p>0.05), and the change in nitrogen balance was not statistically significant after adjustments.
Interpretation
The findings suggest that while L-arginine and Vitamin C supplementation may enhance certain performance and body composition metrics, the clinical significance of these changes, particularly regarding nitrogen balance, remains unclear. The study's limitations, including a small sample size and the lack of significant findings for some outcomes, suggest caution in generalizing these results to broader populations. Further research is needed to confirm these effects and explore the underlying mechanisms.
Key findings
- Significant increase in VO₂max, p<0.001.
- Significant increase in serum testosterone levels, p<0.001.
- Significant reduction in body weight, p<0.001.
- Significant reduction in BMI, p=0.004.
- Significant reduction in body fat, p<0.001.
- Change in nitrogen balance did not reach statistical significance after adjusting for confounders.
Limitations
- Small sample size (n=50).
- Change in nitrogen balance not statistically significant after adjustments.
- Short duration of 45 days.
- No significant changes in GH or cortisol levels.
- Single-site study.