Medical nutrition therapy is a therapeutic approach to treating medical conditions and their associated symptoms via the use of a specifically tailored diet devised and monitored by a registered dietitian or professional nutritionist. The diet is based upon the patient's medical record, physical examination, functional examination, and dietary history.
Its role when administered by a physician, dietitian, or professional nutritionist is to reduce the risk of developing complications in pre-existing conditions, such as type 2 diabetes, as well as ameliorate the effects any existing conditions, such as high cholesterol. Many medical conditions either develop or are made worse by an improper or unhealthy diet.

Dietary and nutritional considerations are fundamental to many complementary and alternative healing approaches.
Many non-Western cultural traditions make little distinction between medicine and food because diet is fundamental to health. Alternative and complementary dietary and nutritional modalities include macrobiotics, vegetarianism, and individualized dietary programs.
Macrobiotics, based on Asian concepts of nutrition, tailors diet to both individual needs and the season.
Vegetarian health diets vary widely: some exclude all animal products, whereas others include milk and/or eggs and/or fish. Many nutritional counselors support the use of supplements to replace nutrients that may be lacking in the diet.
Other nutritional practitioners develop individualized dietary advice for clients, basing their recommendations on an analysis of the individual's unique metabolic characteristics.

Complementary and Alternative Medicines for serious illness. Definitions. CAM modalities. Internet. Accessed on October 1, 2011.