Citrulline is a non-proteinogenic amino acid that plays a role in the body mainly in the urea cycle and arises as an intermediate in the formation of the amino acid arginine. Citrulline occurs naturally in notable amounts in watermelon, which is also where its name comes from.
Because the body links citrulline with arginine via the urea cycle, it is often mentioned in sport in connection with nitric oxide formation, which in turn is associated with the widening of blood vessels.
Relevance for nutrition and sport
Citrulline, especially in the form of L-citrulline malate, is among the more frequently studied substances in the area of training supplements, although the evidence for a noticeable performance increase is mixed overall and shows effects of varying strength depending on the sport and the person.
Amounts commonly cited in research are, as a rough guide, in the range of several grams before training, while the instructions on the product are what count. The guide L-citrulline gives a detailed assessment of citrulline as a training supplement. Individual responses differ noticeably, so blanket expectations of a particular effect make little sense, and everyone should judge their own experience rather than rely on advertising claims alone.
