A recent study conducted at the University of Santa Catarina in Brazil has shed light on the mechanisms behind the antidepressant effects of folic acid.
The study, due to be published in the journal Behavioural Brain Research, suggests that the antidepressant effects exhibited by folic acid may in part be due to it stimulating the same receptors in the brain as opiate drugs like morphine.
It has been known for some time that morphine has mood elevating properties and recently scientists have started to look at its natural counterparts, known as endorphins, as a target for antidepressant therapy. They note the high concentrations of opioid receptors and endorphins in the limbic and hypothalamic areas of the brain, both of which are intimately involved with mood regulation. Opioid receptors and endorphins also interact with the neurotransmitters dopamine and noradrenaline which have long been implicated in depression. It is thought therefore that a deficiency of endorphins may also be involved in depression and that they, and agents that mimic them, may be a useful treatment.
The results obtained by the Brazilian researchers suggest that folic acid may be one such therapeutic agent.
Folic acid is a water soluble B vitamin required for many functions in the body including the production and maintenance of DNA and RNA (the building blocks of life), production of healthy red blood cells, maintenance of healthy homocysteine levels (a risk factor for cardiovascular disease), and the metabolism of protein to produce energy. Good food sources of folic acid include liver, dark green leafy vegetables, brown rice, and some fruits (e.g. oranges and bananas).
The researchers discovered the link between folic acid and the opioid system in rats using the forced swimming test (FST), a standard assessment of a substance's antidepressant activity. They found that the antidepressant effect of folic acid disappeared when the mice were also given drugs that block opioid receptors in the brain. This strongly suggests that folic acid's antidepressant effects are due to its stimulation of these receptors.
To confirm the results the team simultaneously administered sub-therapeutic doses of folic acid and morphine and found that the combination produced an antidepressant effect.
The researchers also believe that folic acid also elicits its antidepressant effects by reducing the activity of another receptor, the NMDA receptor, which when stimulated increases electrical activity in the brain; folic acid therefore having a calming effect.
Given the results and the fact that folic acid is water soluble, and therefore does not build up in the body, it may be useful as an antidepressant either alone or in combination with other therapies.
Other mechanisms by which folic acid may act as an antidepressant include its role as a "methyl donor". Methyl groups are required for the production of mood regulating neurotransmitters, including dopamine and noradrenaline, and folic acid acts as a source of these chemical components in the body.