Links between the ingestion of food and changes of behaviour and emotional state may arise in a variety of ways. A useful attempt to establish a series of definitions was made by a Joint Committee of the Royal College of Physicians and the British Nutrition Foundation, but this failed to take account of the possibility of reproducible psychological reactions, without observable physical changes, occurring independently of the person's awareness of the nature of the food ingested. As this phenomenon is crucial to the subject, a revised set of definitions is proposed here.
