A dietitian is an expert in dietetics; that is, human nutrition and the regulation of diet. A dietitian alters their patient’s nutrition based upon their medical condition and individual needs. Dietitians are regulated healthcare professionals licensed to assess, diagnose, and treat nutritional problems. Dietitians and nutritionists plan food and nutrition programs and supervise the preparation and serving of meals. They help prevent and treat illnesses by promoting healthy eating habits and suggesting diet modifications.