10 μg/d vitamin D food fortification increases vitamin D levels in populations

The investigators found in a review article of 34 publications (2,398 adults: 1,345 intervention (group with vitamin D fortification), 1,053 controls (group without vitamin D fortification) and 1,532 children: 970 intervention, 562 controls), that vitamin D food fortification (at least 10 μg/d) increases circulating 25(OH)D concentrations in populations.

Read more right here:
10 μg/d vitamin D food fortification increases vitamin D levels in populations