A dietitian (also 'dietician', though 'dietitian' is used consistently by professionals) is an expert in food and nutrition.

Dietitians help promote good health through proper eating. They also supervise the preparation and service of food, develop modified diets, participate in research, and educate individuals and groups on good nutritional habits. The goals of the dietary department are to obtain, prepare, and serve flavorsome, attractive, and nutritious food to patients, family members, and health care providers.

In many countries only people who have specified educational credentials can call themselves "dietitians" — the title is legally protected. The term "nutritionist" is also widely used; however, the term nutritionist is not regulated as dietitian is. People may call themselves nutritionists without the educational and professional requirements of registered dietitians.

Dietetic technicians are not the same as dietitians in terms of responsibilities and qualifications. Different professional terms are used in other countries. Although dietitians are a valuable member of the medical multi-disciplinary team, their abilities should not be mistaken for those of physicians. The former are limited to providing only professional dietary advice and are unable to prescribe therapeutic medication or provide a medical consultation.

Types of dietitians

The majority of dietitians are clinical, or therapeutic, dietitians. Clinical dietitians review medical charts and talk with patients' families. They work with other health care professionals and community groups to provide nourishment, nutritional programs and instructional presentations to benefit people of all ages, and with a variety of health conditions. This is accomplished by developing individual plans to meet nutritional needs. These plans include nourishment, tube feedings (called enteral nutrition), intravenous feedings (called parenteral nutrition) such as total parenteral nutrition (TPN) or peripheral parenteral nutrition (PPN), diets, and education. Clinical dietitians provide individual and group educational programs for patients and family members about their nutrition and health.

Clinical dietitians

Clinical dietitians work in hospitals and other health care facilities to provide medical nutrition therapy to patients according to the disease processes, provide individual dietary consultations to patients and their family members and also conduct group educations for other health workers, patients and the public. They coordinate both medical records and nutritional needs to assess the patients and make a plan based on their findings. Some clinical dietitians have dual responsibilities with medical nutrition therapy and in foodservice, described below. In addition, clinical dietitians in smaller facilities will also provide or create outpatient education programs. They work as a team with the physicians, physical therapists, occupational therapists, pharmacists, speech therapists, social workers and nurses to provide care to the patients. Ben Johnson, professor at Harvard Medical School, is a clinical dietitian.