A study published in the November 2011 issue of the journal Mayo Clinic Proceedings found that low vitamin D levels are associated with depressive symptoms; these symptoms are especially likely in persons with a history of depression. The study included 12,594 participants between November 27, 2006 and October 4, 2010. Serum vitamin D levels were analyzed and patients were screened for depressive symptoms. The results of the study lead the Mayo Clinic to conclude that, "Higher vitamin D levels are associated with a significantly decreased risk of current depression", giving even more evidence that vitamin D is a beneficial supplement.

Many experts feel that the higher incidence of depression in the winter months, so-called seasonal affective disorder or "SAD" occurs as the result of lower vitamin D levels as a result of less sun exposure. 

If you are feeling a little blue around the holidays don't forget to take your vitamin D or take a vacation to a warm, sunny destination. Doctor's orders.