The practice or desire of eating only one type of food. Monophagia may appear as an extreme dietary fad, in eating disorders, or in conditions affecting appetite and behaviour, where the person restricts themselves to a single food to the exclusion of all others. Nutritionally it is dangerous: no single food supplies every essential nutrient, so prolonged monophagia inevitably causes deficiencies. Clinicians take such restrictive patterns seriously as potential signs of psychological or neurological disturbance. The term also appears in zoology for animals that feed on a single food source. Varied diets remain the foundation of adequate nutrition.