There is an evidential link between diet, mood and behaviour, but a shortage of formalised educational literature covering the role of nutritional science and its application in the care and treatment of mental health problems. In the U.K., a limited amount of a few types of fruit and vegetables, few wholegrains and little oily fish are consumed. Instead, large quantities of refined carbohydrates, altered fats, intensively reared meat and dairy products are eaten, along with unknown combinations of synthetic chemicals and residues. In some individuals, specific nutritional and environmental factors generate physiological responses which may influence mood, promote anti-social behaviour and trigger overwhelming cravings for certain foods or substances. Nutritional Therapists are not currently part of the multidisciplinary team assessing people suffering from mental health problems. They generally work in private practice with clients on an individual basis. Their role is to improve diet and identify potential food intolerances, hormone imbalances, blood sugar issues, enzyme deficiencies, compromised gut immunity, increased nutrient requirements, a toxic metal burden or chemical sensitivities. Each case is examined on its own merits, given the variety of genetic and environmental differences among individuals. The considerable challenge for the nutritional therapist remains to intervene safely and effectively in mental health conditions which involve multiple complex and interacting mechanisms.