According to the CDC, 33% of Americans have vitamin D levels below sufficiency.1 The definition of sufficiency used by the CDC only takes into consideration vitamin D’s effects on bone health, not the wide range of other elements of good health we now suspect vitamin D to influence. Vitamin D receptors are found to exist in most tissues throughout the human body and research has suggested a relationship between vitamin D and the immune system, cognitive health, hair retention, depression, cancer, and much more.