Use of Folate-Based and Other Fortification Scenarios Illustrates Different Shifts for Tails of the Distribution of Serum 25-Hydroxyvitamin D Concentrations.

BACKGROUND The purpose of food fortification is to affect those at the lower end of the distribution curve for nutrient status while avoiding unintended consequences for those at the high end of the distribution. Vitamin D presents challenges in this regard. OBJECTIVES We used scenarios to model changes in concentrations of serum 25-hydroxyvitamin D [25(OH)D] based on increases made because of assumptions about fortification. We then examined the outcomes for balance between improving serum 25(OH)D status for those at risk of inadequacy while avoiding high concentrations for those not at risk. METHODS Data from NHANES 2001-2006 served as baseline serum 25(OH)D concentrations and were used to model shifts in serum 25(OH)D distribution after application of 3 fortification scenarios, including conceptual scenarios and an experiential predictive scenario we developed with the use of statistical modeling of changes in NHANES serum folate concentrations between prefortification and postfortification time periods. RESULTS All scenarios suggested the possibility of increasing serum 25(OH)D above 125 nmol/L among the proportion of the population at the high end of baseline serum 25(OH)D distribution. The scenario based on serum folate change struck a middle ground between the 2 conceptual scenarios. It predicted a prevalence of 11% <40 nmol/L serum 25(OH)D compared with 17% currently (study baseline), and 8% prevalence of serum 25(OH)D >125 nmol/L compared with <1% currently (study baseline). It also confirmed that fortification affects those at the low end of the status distribution curve differently from those at the high end. CONCLUSIONS Nutrient inadequacy of the type demonstrated by vitamin D--in which the risk is not universal--requires a thorough exploration of the unintended consequences of the overall shift in the distribution of serum 25(OH)D if efforts are made to use fortification to increase the status of persons at risk of deficiency. Fortification is at best a blunt instrument that must be implemented with caution. Moreover, fortification must be preceded by more research to elucidate the dose-response relation between intake and changes in serum 25(OH)D.