Arginine is a semi-essential amino acid that the body can make itself in sufficient amounts under normal conditions, but that should be taken in additionally through food in certain phases of life or when requirements are increased. Among other things, it is a precursor of nitric oxide, a messenger substance involved in the widening of blood vessels.
In food, arginine is found mainly in protein-rich foods such as meat, fish, nuts and pulses. The urea cycle, through which the body disposes of excess nitrogen, is also closely linked to arginine and the related amino acid citrulline.
Relevance for nutrition and sport
Because of its role in nitric oxide formation, arginine is often discussed in sport in connection with blood flow to the muscles during training. The evidence for a noticeable performance increase from additional arginine supplements is inconsistent overall, partly because orally taken arginine is partly broken down in the body before it reaches the bloodstream.
Citrulline, which the body can also convert into arginine, is more often studied in research as an alternative. The guide L-arginine gives a detailed assessment of arginine as a training supplement. Anyone considering targeted supplementation should have realistic expectations of the effect that can actually be expected.
