Nutrition is the scientific study of the effect of diet on health and disease. Despite it's importance to health, it is not a medical specialty, although there is a medical profession, dietitians, who do deal with patients with dietary problems.
Scientific understanding of nutrition started in the late 18th century when several independent researchers noticed that certain diseases were associated with certain types of diet. In the early 20th century, certain substances, then called vitamins were identified as the precise agent that caused and treated the conditions.
In medicine, nutrition and diet have three important ramifications:
- Malnutrition illnesses. Although now rare, certain diseases are now understood to be tied to a particular micronutrient. For example, anemia is often caused by vitamin B-12 deficiency, particularly in vegans.
- Malabsorption illnesses. Several diseases are caused by an inability of certain individuals to digest certain foods, for example, celiac disease is caused when the body cannot process gluten, the primary protein in wheat and wheat products.
- Obesity. With lack of food becoming less of a problem in most of the world, obesity has become one of the conditions that has the greatest remaining effect on human life span.