What about Serotonin?

Serotonin is a neurotransmitter; functions include regulation of appetite, mood and sleep.  Low levels of serotonin can lead to carbohydrate cravings, depression, fatigue, irritability, social withdrawal & sleep disturbances.  

How to influence Serotonin levels via Diet:

Tryptophan is the precursor to serotonin.  Food Sources: almonds, avocado, bananas, beets, brown rice, cashews, chickpeas, miso, peanuts, pecans, pine nuts, tempeh, turkey, whole grain bread

Calcium activates multiple neurotransmitters in the brain including Serotonin.  Food Souces: artichokes, cabbage, green leafy vegetables, kiwi, lima beans, pumpkin seeds, strawberies, watercress, yogurt

Essential Fatty Acids play a role in the formation of hormones, along with proper functioning of neurons & chemical reactions in the brain.  Omega 3's found in chia, flax seed oil, mackerel, salmon, sardine, tuna, walnut oil. Omega 6s found in canola oil, flax, grape seed oil, safflower oil, sunflower oil and wheat germ oil.  Gamma-Lionleic Acid found in borage oil & primrose oil

The B vitamins (primarily Vitamin B6) are also required to produce Serotonin.  Food Sources of B6: bran, cod, garlic, hazelnuts, pistacchios, salmon, spinach, tahini, wheat

It should be noted that severe deficiencies in Serotonin likely need medical attention, but including these foods in your diet can only bring benefit.