These are good sources of the amino acid tryptophan. According to research in the Journal of Neuropsychopharmacology a deficiency of tryptophan can bring on feelings of depression.

This is positively swimming with omega-3. Researchers in the US say people with higher levels of these fatty acids are less likely to suffer from low moods. An 85g fillet provides a biologically useful one to two grams.

Grill 40g of these slippery customers to get your daily fix of vitamin D. Research published in the Archives of General Psychiatry links a D deficiency to an increased risk of depression. It's thought that the vitamin boosts levels of the "feel good" hormone serotonin.