Citrulline is a dietary compound that may have useful health properties in animals and humans. It Citrulline an α-amino acid synthesised either from arginine as a byproduct of the formation of nitric oxide, or from ornithine as a by product of the urea cycle. Citrulline is incorporated into a number of proteins during post transcriptional modification, and so plays an important structural role in protein biochemistry. However, it is also a potent scavenger of hydroxyl radicals, and so is an integral part of the cellular antioxidant defence system in humans. For example some evidence suggests that citrulline is able to improve endothelial function through its ability to scavenge free radicals. Most studies investigating the effects of citrulline supplementation have focussed on the cellular mechanisms by which it may impart antioxidant activity, or on measuring short term biochemical markers of free radical damage. To date there has been little research looking at the longer term health effects of citrulline in humans.
To understand the potential long term effects of citrulline it is therefore necessary to turn to animals studies. Again few long term animals studies have been performed. However recently the long term health effects of citrulline were investigated in rats. Twenty month old rats (rats tend to live for around 2 to 3 years) were fed either a normal rat chow ad libitum diet for 12 weeks or ad libitum diet that had been enriched with citrulline. The citrulline diet provided approximately 1 gram per kg of body weight. The rats receiving the citrulline in their diet had a lower total mortality compared to the control rats. In addition, the citrulline fed rats had 9 % less body mass, between 14 and 48 % greater muscle mass and 13 % lower fat mass compared to the control rats. A measure of antioxidant status in the rats also showed a significant reduction in susceptibility to free radical damage. Citrulline supplements, or naturally increasing citrulline levels, may therefore have beneficial health effects (at least in elderly rats).
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