What is Citrulline?
Citrulline is an amino acid, one of endogenous, so we can synthesize it ourselves. It is formed mainly in the small intestine (mainly from proline and glutamine), and one of its main tasks is to be a substrate for the production of arginine in the body (the process takes place primarily in the kidneys – this place is about 60% of systemic arginine synthesis). L-arginine, in a complex NO (nitric oxide) formation process, is also a substrate for the production of citrulline in the body.
In sport, it is usually used as a substance to maximize the production of NO, and as a result lead to the increase of muscle perfusion (muscle pump), decrease in blood pressure and, theoretically, better nutrition of the muscle, its regeneration and development. Supporters of citrulline supplementation are many, there are also plenty of opponents, and what about science statement?
Fresh scientific reports
In March, a systematic review was published with a meta-analysis by Eric Trexler and colleagues to provide up-to-date information on the effect of citrulline supplementation on strength and power in high-intensity efforts.
How was work composed?
A review of the literature was undertaken, segregating the work into the useful and other that they rejected. It was important that the experiment included exercises involving large muscle groups, sets of strength exercises or sprints that lasted a maximum of half a minute. All attempts involving single repetition or small muscle groups were discarded. There were also no experiments in which placebo was not used, as well as those where a portion of citrulline was less than 3g and/or taken later than 30 minutes before exercise. Another criterion for exclusion was the use of a matrix of citrulline with another compound with a documented ergogenic effect.
As a result, they selected 12 experiments, including 198 people. Due to such restrictive inclusion criteria, it turned out that the heterogeneity of the results was small (that is, the results were consistent)!
It turned out that, compared to placebo, citrulline significantly improves the strength and power in the highly intense efforts. Sadly, it was observed that the effect of supplementation, although statistically significant, is characterized by a small strength (size) of the effect, and hence – in most cases, practical application will not make sense. The authors hope for citrulline supplementation in high-level players, where minimal differences may decide about the place on the podium, but anxiety raises two issues
It’s just a hypothesis, and we’ll have to wait for more evidences
Experienced by experience (evidence regarding nitrates and beets in the context of NO production) – I would expect a weaker effect in elite class athletes than in the general population of active people.
There are no miracles, unfortunately, with a short, high-intensity effort, citrulline will not do much. So far, a number of positive effects of supplementation with this amino acid have been demonstrated, but in this particular matter, it does not prove to be very useful.