These protein building-blocks are the raw materials for neurotransmitters and other mood-regulating brain chemicals. Those most directly related to mood and depression are tryptophan, phenylalanine and tyrosine.
Essential fatty acids
Neural membranes contain lots of omega-3 fatty acids, so a deficiency in these fats impairs nerve function, and contributes to mental and nervous disorders such as depression, aggression and schizophrenia.
B1 is needed by the brain to help convert glucose into fuel and, if it runs out, mental energy dwindles, resulting in possible depression, irritability, anxiety and even suicidal thoughts. Mice fed a thiamine-deficient diet had marked amnesia and mood abnormality.
In a placebo-controlled study of 33 children with disturbed behaviour, it was found that only one of the children failed to respond to B3 therapy, and all relapsed to their former behavioural problems when the treatment was stopped.
As this nutrient is essential for converting tryptophan to serotonin, it's no surprise that there's a strong correlation between B6 deficiency and depression. Women taking the Pill, known to deplete levels of B6 and to speed the breakdown of tryptophan, are often advised to supplement with B6 as a natural antidepressant.
Important for the formation of red blood cells, a deficiency can lead to pernicious anaemia, characterised by mood swings, paranoia, irritability, confusion, dementia, hallucinations or mania - symptoms that can easily be mistaken for mental illness.
Folic acid (folate)
A water-soluble B vitamin necessary for the production and upkeep of new cells, a deficiency is believed to be a major cause of schizophrenia. One study found that over a third of patients with schizophrenia had borderline or definite folate deficiency. However, too much folic acid may worsen psychotic behaviour or adversely interact with antipsychotic drug treatments.
This powerful antioxidant is essential for fighting free radicals from pollution and toxins, and plays a role in maintaining mood. When 40 chronic psychiatric patients took a vitamin C supplement, those taking the vitamin (rather than a placebo) showed improvement in their depressive symptoms.
This works in tandem with potassium and calcium, and is important for more than 300 biochemical reactions in your system. It maintains normal muscle and nerve function as well as helping energy metabolism and protein synthesis. A deficiency can lead to fidgeting, restlessness, anxiety, psychomotor instability and learning difficulties among children with a normal IQ.
Essential for the formation of haemoglobin, the oxygen-carrying protein component of blood, a deficiency leads to anaemia, resulting in irritability and poor attention.
Calcium. While often associated with strong bones, calcium is also involved in blood-clotting, nerve function and regulating blood pressure. Too little of this mineral - which goes hand-in-hand with magnesium deficiency - is associated with depression.
Necessary for healthy brain function, low levels often lead to irritability, mental slowness and emotional disorders. The findings of one double-blind placebo-controlled study of children with ADHD suggest zinc deficiency may lie at the root of it.