The foods we eat have a direct influence on our mental health. Our mood is determined by the presence of certain neurotransmitters, or chemical messengers, in the brain. Serotonin, dopamine and norepinephrine are the three neurotransmitters that have the most influence over our mood. Deficiencies in these neurotransmitters are associated with depression, anxiety, ADHD, difficulty sleeping, fatigue and irritability.