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Citruline Malate

Also known as: Citrulline malate, CitMal, L-Citrulline Malate

Overview

Citrulline malate is a compound consisting of the non-essential amino acid L-citrulline and malic acid (malate). L-citrulline is naturally found in watermelons, while malate is an intermediate in the Krebs cycle. As a dietary supplement, citrulline malate is primarily used to enhance exercise performance by improving muscle endurance, reducing fatigue, and enhancing recovery. It is believed to increase nitric oxide production, improve blood flow, and enhance ATP production through malate's role in energy metabolism. Research on citrulline malate is considered moderately mature, with multiple randomized controlled trials and meta-analyses conducted, though findings are mixed. Several systematic reviews and meta-analyses exist, with some showing ergogenic benefits, particularly in endurance and repetition performance, while others show no significant effect on muscle strength.

Benefits

Citrulline malate supplementation has demonstrated potential benefits for muscular endurance. Meta-analyses indicate that acute citrulline malate supplementation before strength training can increase total repetitions performed during resistance exercise, suggesting improved muscular endurance. These effects are classified as small to medium. Furthermore, citrulline malate may improve aerobic and anaerobic endurance performance by enhancing nitric oxide-mediated vasodilation and energy metabolism. These benefits are primarily observed in healthy, resistance-trained adults and young healthy adults engaged in endurance exercise. While effects on repetition performance are statistically significant, effects on muscle strength are negligible and statistically non-significant. Benefits are typically observed acutely, with supplementation taken shortly before exercise.

How it works

Citrulline malate works through two primary biological pathways. First, citrulline is converted to arginine in the kidneys, which then serves as a substrate for nitric oxide synthase to produce nitric oxide (NO). Nitric oxide is a vasodilator that improves blood flow. Second, malate participates in the Krebs cycle, potentially enhancing ATP production and reducing fatigue. This enhances endothelial function via NO production and supports energy metabolism in muscle cells. Citrulline malate is well absorbed orally, with citrulline showing higher bioavailability than arginine itself.

Side effects

Citrulline malate is generally considered safe, with no serious adverse effects reported in clinical trials. The most common side effect is mild gastrointestinal discomfort in some individuals. Uncommon and rare side effects are not consistently reported in high-quality studies. Potential drug interactions include additive effects with medications that affect blood pressure or nitric oxide pathways, so caution is advised. There are no well-established contraindications, but caution is advised in hypotensive patients. Limited data exists for pregnant or breastfeeding women and clinical populations, so use in these populations should be approached with caution.

Dosage

Studies commonly use doses around 6-8 grams of citrulline malate taken 30-60 minutes before exercise. This range is considered the optimal dosage for performance benefits. Doses up to 10 grams per day have been used without adverse effects, suggesting this as a maximum safe dose. Acute pre-exercise ingestion is typical. Citrulline malate is available in powder or capsule forms standardized to citrulline malate content. It should be taken with water, and no known cofactors are required for absorption.

FAQs

Does citrulline malate increase muscle strength?

Current evidence does not support a significant effect on muscle strength in resistance-trained individuals.

Is it safe to take daily?

Citrulline malate is generally safe with minimal side effects reported.

When should it be taken for best results?

It should be taken approximately 30-60 minutes before exercise.

How soon will I notice effects?

Effects on endurance and repetition performance may be observed acutely during the exercise session.

Is it better than arginine supplementation?

Citrulline malate has better bioavailability and is more effective at raising plasma arginine and nitric oxide levels.

Research Sources

https://pubmed.ncbi.nlm.nih.gov/34010809/ – This meta-analysis of RCTs (n=138) found no significant effect of citrulline malate on muscle strength in resistance-trained adults. The study assessed both upper and lower limb strength and found no difference between them. The authors noted the small number of studies and heterogeneity in protocols as limitations.
https://pubmed.ncbi.nlm.nih.gov/34176406/ – This systematic review and meta-analysis focused on the acute effect of citrulline malate on repetition performance during resistance exercise. The findings indicated that citrulline malate supplementation prior to exercise improves total repetitions performed, suggesting enhanced muscular endurance with small to moderate effect sizes. The authors noted variability in dosing and exercise protocols as limitations.
https://www.tandfonline.com/doi/full/10.1080/15502783.2023.2209056 – This systematic review/meta-analysis on endurance performance found that acute citrulline ingestion shows ergogenic effects on endurance performance in young healthy adults. The authors suggest that the mechanism of action is likely via nitric oxide-mediated mechanisms. The authors noted some heterogeneity in exercise types and populations as limitations.
https://www.mdpi.com/2072-6643/14/17/3479 – This systematic review and meta-analysis investigated the effects of citrulline supplementation on physical performance in healthy individuals. The study found that citrulline supplementation can improve muscle endurance and aerobic performance, particularly in activities involving sustained effort. The authors highlighted the importance of considering individual variability and training status when interpreting the results.
https://journals.humankinetics.com/view/journals/ijsnem/31/4/article-p350.xml – This study investigated the effects of citrulline malate supplementation on anaerobic power and muscle soreness following resistance exercise. The results indicated that citrulline malate supplementation may reduce muscle soreness and improve anaerobic performance during repeated bouts of high-intensity exercise. The authors suggested that these effects may be attributed to increased nitric oxide production and improved energy metabolism.