Vitamin D deficiency, which is common in children and adults, causes rickets, osteomalacia [softening of the bones due to defective bone mineralization, with symptoms such as diffuse body pains, muscle weakness, bone fragility], and osteoporosis.
Most organs and immune cells have a vitamin D receptor, and some also have the capacity to metabolize 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D.
1,25-Dihydroxyvitamin D is a potent immunomodulator that also enhances the production and secretion of several hormones, including insulin.
Vitamin D deficiency has been associated with increased risk of type 1 diabetes.
Glycemic control and insulin resistance are improved when vitamin D deficiency is corrected and calcium supplementation is adequate.
25-Hydroxyvitamin D (measure of vitamin D status) of less than 20 ng/mL is vitamin D deficiency and 21 to 29 ng/mL is insufficiency.
Children and adults need at least 1000 IU of vitamin D per day to prevent deficiency when there is inadequate sun exposure.
Source: Current Diabetes Reports, Oct 2008;8(5):393-8. PMID: 18778589, by Holick MF. Department of Medicine, Section of Endocrinology, Nutrition, and Diabetes, Boston University School of Medicine, Boston, Massachusetts, USA. [E-mail: firstname.lastname@example.org ]