The role of vitamin D in critical illness.

The role of vitamin D in critical illness is under investigation. Recent data indicate declining levels of serum vitamin D in multiple adult populations. Deficiencies have been strongly linked to infectious processes and certain chronic disorders. Vitamin D deficiency that is present at the onset of critical illness may impact the severity of illness and contribute to less-than-optimal outcomes. This article describes the function of vitamin D, the effects that deficiencies have on body systems, and the emerging role of vitamin D deficiency for critically ill patients.