Vitamin D as a modifiable risk factor in critical illness: questions and answers provided by observational studies

Abstract

Vitamin D is essential to optimal health. Studies dating back to the early 1900’s convincingly demonstrate that a state of vitamin D deficiency, acquired through limited sun exposure and avoidance of vitamin D-rich foods can lead to stunted growth, bone disease, and hypocalcemic seizures. Over the past few decades, a rising body of epidemiological literature has also suggested that vitamin D deficiency predisposes to a wide variety of disease states outside of the musculoskeletal system. For example, vitamin D status has been associated with diseases involving dysregulation of the immune (type I diabetes, cancer), cardiovascular (heart failure, cardiomyopathy), and respiratory systems (bronchiolitis, pneumonia). Strong biological plausibility supporting these epidemiological findings has been provided, including basic science studies showing the presence of vitamin D receptors on a large number of diverse cell types (e.g. white blood cells, myocytes), and animal studies demonstrating disease occurrence in genetically(vitamin D