Vitamin D is derived from skin production through exposure to ultraviolet light and from oral intake of natural foods, fortified foods and supplements. While the principal source of vitamin D is skin production, oral intake has primacy over sunlight exposure in both the correction and prevention of privational vitamin D deficiency. Vitamin D deficiency is associated causally with rickets in childhood and osteomalacia in adulthood, but the evidence is inconsistent and inconclusive for a causal association with cancer, infections, autoimmune diseases and cardiovascular disease.