The immune support benefits of the sunshine vitamin have grown in recent years. Vitamin D receptors are expressed on immune cells (B cells, T cells and antigen presenting cells) and these immunologic cells are all are capable of synthesizing the active vitamin D metabolite.
A 2010 study by scientists from the University of Copenhagen found that vitamin D is necessary to trigger T cells – the immune system’s killer cells – into action, and insufficient levels of the vitamin mean the cells remain dormant and inactive.
“Scientists have known for a long time that vitamin D is important for calcium absorption and the vitamin has also been implicated in diseases such as cancer and multiple sclerosis, but what we didn't realize is how crucial vitamin D is for actually activating the immune system – which we know now,” they wrote in Nature Immunology(Vol. 11, pp. 344–349, Marina von Essen et al.).
A 2013 study by scientists at the University of Tromso reported that blood levels of vitamin D may affect the expression of genes linked to immune health and inflammation: Data from 218 people indicated that vitamin D levels are linked to “molecular pathways that may ultimately affect the potential onset of diseases”, according to findings published in the European Journal of Clinical Nutrition.