Vitamin D Deficiency Common Even in Southern U.S.

Sun exposure is an important source of vitamin D. The definition of vitamin D deficiency has changed in recent years and is still controversial, but a widely accepted standard is a serum concentration of <20 ng/mL of 25(OH)-hydroxyvitamin D [25(OH)D]. As many as 30% of people living in the northern U.S. — where exposure to sunlight is relatively limited — have vitamin D deficiency. Is deficiency less common in sun-drenched southern areas?

Investigators in southern Arizona studied 637 adults and found vitamin D deficiency in 23% of whites, 38% of Hispanics, and 56% of blacks. As expected, those who reported greater sun exposure had higher levels of 25(OH)D, and levels were higher in summer than in winter.