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Head-to-head evidence comparison — which supplement is right for you?
Casein Protein wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
3 of 3 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
8 of 10 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both Casein Protein and L-Citrulline have evidence — compare verdict strength side-by-side.
30-40g before bed
30-60 minutes before bed, Between meals for sustained protein
Micellar Casein powder
3-6g (or 6-8g citrulline malate)
30-60 minutes before exercise, Or split doses throughout day
L-Citrulline powder (pure form)
Overnight
2-4 weeks
4-8 hours
Always
1-2 weeks
24-48 hours post-exercise
30-60 minutes
With doses >10g
Effects of supplementation with milk protein on glycemic parameters: a GRADE-assessed systematic review and dose-response meta-analysis
Nutrition journal (2023) · Meta analysis · n=1851
The findings of this study suggest that supplementation with MP may improve glycemic control in adults by reducing the values of fasting insulin, FBG, and HOMA-IR.
Pre-Sleep Casein Supplementation, Metabolism, and Appetite: A Systematic Review
Nutrients (2021) · Systematic review · n=11
However, it remains unclear what the effect of this nutritional strategy is on non-muscular parameters such as metabolism and appetite in both healthy and unhealthy populations.
Pre-sleep protein ingestion to improve the skeletal muscle adaptive response to exercise training
Nutrients (2016) · Systematic review · n=387
Pre-sleep protein enhances training adaptations
Absence of Effects of L-Arginine and L-Citrulline on Inflammatory Biomarkers and Oxidative Stress in Response to Physical Exercise: A Systematic Review with Meta-Analysis
Nutrients (2023) · Meta analysis · n=1080
We observed no difference between pre- vs. post-exercise for oxidative stress (subtotal = -0.21 [CI: -0.56, 0.14], p = 0.24, and heterogeneity = 0%.
Effects of Citrulline or Watermelon Supplementation on Body Composition: A Systematic Review and Dose-Response Meta-Analysis
Nutrients (2025) · Meta analysis
Overall, CIT supplementation had no substantial effects on body mass index (BMI), body weight, fat mass (FM), waist circumference (WC), body fat percentage (BFP), and fat-free mass (FFM).
Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials
Journal of the International Society of Sports Nutrition (2021) · Meta analysis
No effect on exercise performance following consumption of foods rich in L-citrulline was identified (SMD=-0.03, p=0.24).
Based on systematic review (n=387) showing pre-sleep casein enhances training adaptations and increases muscle fiber size. Optimal dose identified as 30-40g. Limited to pre-sleep timing and requires concurrent exercise training.
Meta-analysis showed significant reduction in muscle soreness 24h post-exercise but effect size was modest. Studies primarily used citrulline malate form.
AI-estimated from published studies. Interpret as directional guidance.
Casein Protein has a higher evidence score (9/10 vs 9/10) and wins in 2 of 3 categories.
For build strength & muscle, Casein Protein has a higher relevance score (88 vs 70).
No known interactions between Casein Protein and L-Citrulline have been documented in our database. However, always consult a healthcare provider before combining supplements.