A recent study from the University of Colorado shows that levels of Vitamin D in Americans have dropped dramatically in the last two decades.

Another recent study shows a link between disease progression in people with undifferentiated connective tissue diseases and the development of more serious autoimmune conditions, including rheumatoid arthritis and systemic lupus erythematosus.

As many as 75 percent of Americans have vitamin D deficiency, with higher levels seen in Hispanics and African Americans.