I haven't really read through this thread probably...but in addition to fresh fruit, veg....fresh oily fish is excellent for mental health. Although you wouldn't know it looking at your average UK diet, fresh oily fish is considered an an essential component for human physiology. Taking fish oil tablets is a minimum requirement. Salmon is excellent.....tuna (not caned) and mackeral are also great, but dont eat to much mackeral or tuna and do not give to babies or pregnant women at all (not that you are likely to walk around handing mackeral to pregnant women), due to the potential of heavy metal toxins, such as mercury. Salmon is a safe bet.
Oily fish contain the essential fatty acids DHA and EPA, both are shown to play a role in good mental health and brain functioning, as well various other aspects of health. Supplementing a diet of healthy fish with white fish is also a good idea. Eat oily fish at least three times a week...and even more if you can.
Sorry for the advertisement....its my industry. I eat salmon about 5 times a week...and as you are all aware, I am the very picture of perfect mental health.