Citrulline is an amino acid that can be found in its highest dietary concentrations in watermelon, squash, cucumbers and pumpkins (reference 1). Citrulline has a very similar effect in the body as Arginine, serving as a key player in the Nitric Oxide cycle. Similar to Arginine, Citrulline helps greatly with increased blood-flow and instigates the benign ‘pump’ sensation associated with muscle contraction.
Supplementing with Citrulline has been documented as increase the presence of Arginine in in the blood (reference 2) in addition to improving muscular ATP efficiency (ATP is the compound your body uses to create energy). Citrulline is absorbed much more readily in the gut than Arginine, allowing for more effective nutrient uptake and ultimately a better blood flow during a workout.
Citrulline has also demonstrated benefits in regard to restoration of muscle protein synthesis (references 4-5) as well as improved muscular functionality following food restriction (reference 6). In addition, trained athletes supplementing with Citrulline may experience a temporary boost in growth hormone concentrations when exercising (reference 3).
Large doses (over 10g) have been seen to result in diarrhea.
Citrulline has been seen to potentially positively interact with leucine’s mTOR signaling, allowing for improved muscle growth and strength improvement. In addition, the presence of Citrulline and Arginine tend to have an amplification effect on the effects of the other (reference 3).
Recommended doses for sports performance enhancement can be as high as 6-8g daily.
1. Kaore SN, Amane HS, Kaore NM Citrulline: pharmacological perspectives and its role as an emerging biomarker in future . Fundam Clin Pharmacol. (2013)
2. Rougé C, et al Manipulation of citrulline availability in humans . Am J Physiol Gastrointest Liver Physiol. (2007)
3. Sureda A, et al L-citrulline-malate influence over branched chain amino acid utilization during exercise . Eur J Appl Physiol. (2010)
4. Le Plénier S, et al Effects of leucine and citrulline versus non-essential amino acids on muscle protein synthesis in fasted rat: a common activation pathway. Amino Acids. (2012)
5. Osowska S, et al Citrulline modulates muscle protein metabolism in old malnourished rats . Am J Physiol Endocrinol Metab. (2006)
6. Faure C, et al Leucine and citrulline modulate muscle function in malnourished aged rats . Amino Acids. (2012)