University of Toronto researchers argue that the optimal vitamin D-3 requirement probably is much higher than the current recommended daily allowance.
"The physiologic range for circulating 25-hydroxyvitamin D3 [25(OH)D; the measure of vitamin D nutrient status] concentration in humans and other primates extends to beyond 200 nmol/L (>80 ng/mL). This biologic 'normal' value is greater than current population norms for 25(OH)D. Concentrations of 25(OH)D that correlate with desirable effects extend to at least 70 nmol/L, with no obvious threshold," stated R. Vieth and colleagues.