A report in the journal, Journal of Leukocyte Biology, showed that levels of vitamin D3 below 20 ng/ml led to a higher incidence of viral infections, cancer, and autoimmune disorders. This, of course, suggests that supplementing with vitamin D3 could help prevent or treat these conditions.
Low levels of vitamin D3 lead to higher production of antibodies (the Th 2 immune system), but lower levels of cell mediated immunity (the Th 1 immune system) that we need to fight viral infections, certain cancers, and autoimmune diseases.
With the epidemic of vitamin D deficiency, it is especially important that we replace people who are ill, especially in our hospitals, with vitamin D3 supplementation. Levels of vitamin D3 below 20 ng/ml leads to a higher risk of fractures, heart attacks, cancer, and all cause mortality, especially in the elderly.