Depressed people have lower levels of arginine, study finds

People with major depressive disorder (MDD) have reduced arginine levels, according to a new study by the University of Eastern Finland.

Arginine is an amino acid which the body uses to produce nitric oxide, a nervous system and immune defence mediator that also plays a role in vascular regulation.

The study, which has been published in the Journal of Affective Disorders, shows that people suffering from MDD have reduced arginine bioavailability.

Toni Ali-Sisto, the study’s lead author, said: ‘It is possible that depression-induced inflammatory responses lead to reduced arginine levels. 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.’

The study involved 99 adults with diagnosed major depressive disorder and 253 non-depressed controls. The concentrations of three amino acids, namely arginine, citrulline and ornithine, were analysed from fasting glucose samples. The findings were then compared between the depressed and the non-depressed controls.

People with depression had weaker arginine bioavailability than their non-depressed controls. The use of anti-depressants or anti-psychotics did not affect the concentrations, either. There were also no clear differences in the concentrations measured from people who had recovered from depression and people who remained depressed.

‘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. That’s an area for further research,’ Ali-Sisto says.