According to the Mayo Clinic:
The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It is used, alone or in combination with calcium, to increase bone mineral density and decrease fractures. Recently, research also suggests that vitamin D may provide protection from osteoporosis, hypertension (high blood pressure), cancer, and several autoimmune diseases.
Digging a little further into the studies that have been done on Vit D deficiency, some other potential problem areas include mood disorders:
Some studies suggest an association between low vitamin D levels in the blood and various mood disorders, including depression, seasonal affective disorder (SAD), and premenstrual syndrome. Also vitamin D supplementation may improve symptoms of depression associated with seasonal affective disorder.
According to my doctor, the healthy range for Vitamin D levels are between 30 – 100. Mine came in at a whopping 10. So I think I can safely say I’m Vit D deficient. They have me taking 2,000 units of Vit D daily as a supplement. I’m anxious to see if anything improves in my mood.