Intellectual disability and nutrition-related health.

Intellectual disability (ID) is a condition that affects approximately 1% of the population (Maulik et al, 2011). The numbers may differ across nations, owing to different systems and diagnosis entries or lack of such, but usually range between 0.6 and 3% (Stromme & Valvatne, 1998). Persons with ID are a heterogeneous group with different diagnoses and different levels of intellectual ability. These range from profound (IQ < 20) and serious ID (IQ 20-34) to moderate (IQ 35-49) and light ID (IQ 50-69); this roughly translates into the intellectual capacity of children between 3-12 years of age. More than 75% of persons with ID have the mild form and their intellectual capacity and potential may be underestimated in some cases if IQ is the only diagnostic criteria. However, the range in itself is an important factor to take into account when addressing nutrition and health issues. It is further important to recognize that ID is also a feature of several rare disorders, and many disorders not yet identified, adding to the complexity of this group.