Sports activities drinks with quick carbohydrates that endurance athletes drink throughout coaching periods, and likewise protein shakes that bodybuilders down earlier than pumping iron, most likely work higher in the event that they comprise a few grams of L-citrulline [structural formula on the right]. Scientists at Maastricht College Medical Centre within the Netherlands found that L-citrulline boosts the physique’s nutrient uptake throughout exertion.

Pre/intra/post-workout diet
Peri-workout-nutrition is a tried and examined performance-enhancing strategie in all areas of sport. Ingesting further carbohydrates throughout a coaching session helps endurance athletes obtain higher instances, and quickens the restoration of glycogen reserves within the muscle groups. Bodybuilders accumulate extra muscle mass, and get better quicker, in the event that they ingest a portion of proteins or amino acids simply earlier than coaching.

However throughout intensive exertion the digestive tract turns into much less lively, so the uptake of amino acids and carbohydrates decreases. Because of this the added worth of peri-workout-nutrition is proscribed. For instance, the optimum quantity of protein that bodybuilders can soak up earlier than and after exercises just isn’t very massive: 18 g current research recommend. Dutch scientists reported already years in the past that caffeine can need to some extent a optimistic impact, however little has been executed with this info.

The researchers in Maastricht have been curious whether or not supplementation with L-citrulline, an amino acid that’s produced when L-arginine oxidises, may enhance the functioning of the small gut throughout train. The capillaries within the intestines change into narrower throughout exertion as a result of the physique offers precedence to supplying the muscle groups with oxygen and vitamins. L-Citrulline converts into L-arginine within the intestines, and enzymes within the blood vessels of the intestine cells can use L-arginine to provide nitrogen monoxide [NO].

Nitrogen monoxide causes blood vessels to widen, thus bettering the oxygen provide to the intestine cells. It additionally allows extra vitamins to be transported from the digestive tract to the physique. At the very least, that’s what you’d anticipate.

The researchers received educated endurance athletes to cycle for an hour on two totally different events. The depth was that of 70 % of their maximal load.

Half an hour earlier than beginning to cycle the themes got a placebo on one event and on the opposite 10 g L-citrulline. The researchers selected to not experiment with L-arginine, as many individuals get acute diarrhoea the primary time they ingest 10 g L-arginine. As well as, the physique breaks L-arginine down quick.

After taking a placebo the focus of intestinal fatty-acid binding protein [I-FABP] rose within the topics’ blood. This protein is often present in intestine cells. If these disintegrate on account of intensive exertion, then the focus of I-FABP within the blood will increase. The I-FABP focus did rise much less if the themes had been given L-citrulline earlier than beginning to cycle.

Whereas the themes cycled the researchers used transportable microscopes to look at the blood vessels underneath the athletes’ tongues. If these widened the blood vessels of their intestines most likely did the identical. The figures above present that biking with a placebo brought on the blood vessels underneath the tongue to change into narrower, however supplementation with L-citrulline did trigger them to widen.

“The present research demonstrates {that a} single oral dose of L-citrulline previous to train preserves splanchnic perfusion and reduces intestinal damage throughout train”, the Dutch write. “The mechanism most likely entails elevated arginine availability for NO-mediated vasodilatation. These information recommend oral L-citrulline supplementation to be a promising technique to enhance gastrointestinal blood movement and forestall intestinal damage in athletes with out hostile gastrointestinal results as noticed for arginine.”

L-citrulline improves splanchnic perfusion and reduces intestine damage throughout train.


Splanchnic hypoperfusion is a physiological phenomenon throughout strenuous train. It has been related to gastrointestinal signs and intestinal damage and should hamper athletic efficiency. We hypothesized that L-citrulline supplementation improves splanchnic perfusion and reduces intestinal damage by enhancing arginine availability. The intention of this research was to find out the impact of L-citrulline consumption on splanchnic perfusion, intestinal damage, and barrier perform throughout train.

On this randomized, double-blind crossover research, 10 males cycled for 60 min at 70% of their most workload after L-citrulline (10 g) or placebo (L-alanine) consumption. Splanchnic perfusion was assessed utilizing gastric air tonometry. Sublingual microcirculation was evaluated by sidestream darkish discipline imaging. Plasma amino acid ranges and intestinal fatty acid binding protein concentrations, reflecting enterocyte harm, have been assessed each 10 min. Urinary excretion of sugar probes was measured to judge intestinal permeability adjustments.

Oral L-citrulline supplementation enhanced plasma citrulline (1840.3 ± 142.3 µM) and arginine ranges (238.5 ± 9.1 µM) in contrast with that in placebo (45.7 ± 4.8 µM and 101.5 ± 6.1 µM, respectively, P