Arginine is an amino acid readily found in turkey, chicken, soybeans and peanuts, but it is in low supply in those who are chronically depressed according to researchers from the University of Eastern Finland. The body uses arginine to produce nitric oxide, which boosts the immune system and helps improve blood flow.
Scientists tested the levels of amino acids arginine, citrulline and ornithine in 99 people at Kuopio University Hospital who were diagnosed with major depressive disorder. Those results were then compared to 253 other patients who were not diagnosed as depressed and the findings were clear. The arginine levels were low in all of the depressed people according to the study published in the Journal of Affective Disorders.
Researchers were unsure of the link between depression and low arginine levels and said more work needed to be done in order to determine if arginine supplements could aid in reversing depression. "Although our study shows that people with depression have reduced arginine bioavailability, this doesn't mean that taking an arginine supplement would protect against depression,” said lead study author Toni Ali-Sisto. “That's an area for further research.”
The global arginine bioavailability ratio, GABR, is used to determine the body's arginine levels, which reflects the body’s ability to produce nitric oxide. Low arginine levels are also a known risk factor for the development of cardiovascular disease.
"It is possible that depression-induced inflammatory responses lead to reduced arginine levels,” Ali-Sisto said. “This may result in insufficient production of nitric oxide for the needs of the nervous system and circulation. However, we don't know yet what exactly causes reduced arginine bioavailability in people with depression."
Researchers followed up with subjects after eight months and were surprised to learn there was not a large difference in the arginine levels of those who had experienced a remission of their depression. “Arginine bioavailability was slightly higher in people who had recovered from depression than in people who remained depressed,” Ali-Sisto said. “However, a more extensive set of data and a longer follow-up period are necessary for estimating arginine's role in depression recovery."