Advances in Vitamin D nutritional physiology since publication of the DRIs in 1997 are briefly summarized. Available data indicate that (1) Vitamin D's canonical function, optimizing intestinal calcium absorption, is fully expressed at serum 25-hydroxyvitamin D (25OHD) concentration of approximately 80nmol/L; (2) elevated parathyroid activity, typical of aging populations, is minimized at the s...

Nutrition is complex-and seemingly getting more complicated. Most consumers are familiar with "essential nutrients," e.g., vitamins and minerals, and more recently protein and important amino acids. These essential nutrients have nutrient reference values, referred to as dietary reference intakes (DRIs) developed by consensus committees of scientific experts convened by the Institute of Medicin...