Bioavailability of Vitamin D and Its Metabolites in Black and White Adults

Vitamin D deficiency has become a global health problem that has been associated not only with metabolic bone disease but also with many chronic illnesses.1 The definition of vitamin D deficiency has been controversial, in part owing to the interpretation of surrogates associated with vitamin D status. The Institute of Medicine concluded that to maximize bone health, the level of 25-hydroxyvitamin D should be higher than 20 ng per milliliter.2 Others have relied on parathyroid hormone levels to assess vitamin D status, arguing that such levels reach a nadir and plateau when 25-hydroxyvitamin D levels are 30 to 40 ng . . .