25(OH)D(3)-enriched or fortified foods are more efficient at tackling inadequate vitamin D status than vitamin D(3)

The ability to synthesise sufficient vitamin D through sunlight in human subjects can be limited. Thus, diet has become an important contributor to vitamin D intake and status; however, there are only a few foods (e.g. egg yolk, oily fish) naturally rich in vitamin D. Therefore, vitamin D-enriched foods via supplementing the animals’ diet with vitamin D or vitamin D fortification of foods have been proposed as strategies to increase vitamin D intake. Evidence that cholecalciferol (vitamin D(3)) and calcifediol (25(OH)D(3)) content of eggs, fish and milk increased in response to vitamin D(3) supplementation of hens, fish or cows’ diets was identified when vitamin D-enrichment studies were reviewed. However, evidence from supplementation studies with hens showed only dietary 25(OH)D(3), not vitamin D(3) supplementation, resulted in a pronounced increase of 25(OH)D(3) in the eggs. Furthermore, evidence from randomised controlled trials indicated that a 25(OH)D(3) oral supplement could be absorbed faster and more efficiently raise serum 25(OH)D concentration compared with vitamin D(3) supplementation. Moreover, evidence showed the relative effectiveness of increasing vitamin D status using 25(OH)D(3) varied between 3·13 and 7·14 times that of vitamin D(3), probably due to the different characteristics of the investigated subjects or study design. Therefore, vitamin D-enrichment or fortified foods using 25(OH)D(3) would appear to have advantages over vitamin D(3). Further well-controlled studies are needed to assess the effects of 25(OH)D(3) enriched or fortified foods in the general population and clinical patients.