The effects of vitamin D-fortified foods on circulating 25(OH)D concentrations in adults: a systematic review and meta-analysis.

Improvement of vitamin D status of the general population has been a challenge for policymakers. We conducted a meta-analysis to evaluate whether vitamin D-fortified products can be a suitable solution for tackling vitamin D deficiency. Our secondary objective was to determine the effect of some variables including age, latitude and BMI on efficacy of this strategy. MEDLINE, PubMed, Embase, Cochrane Library and Google Scholar were searched and 231 studies were found in a preliminary search. After screening of titles and abstracts, 23 studies were selected. Pooled data comparing fortification with vitamin D +/- Ca with control showed statistically significant effect on total 25(OH)D concentrations (2002 participants, mean difference (MD): 25·4 nmol/l, (95 % CI 19·5, 31·3)). The subgroup analysis by duration of intervention (less than 12 weeks v. more than 12 weeks) and type of vehicle (dairy product, juice, grain product, oil and combination of dairy and grain products), isoform of the vitamin (D3v. D2) and dose of the fortificant (≥ 1000 IU/d v. < 1000 IU/d) also indicated significant effect of fortification with vitamin D on serum 25(OH)D concentrations. In conclusion, the circulating 25(OH)D response to vitamin D-fortified food consumption is influenced by age, BMI and the baseline 25(OH)D concentrations. Notwithstanding, an average of 2 nmol/l increase in circulating 25(OH)D concentration for each 100 IU vitamin D intake per d is expected for general adult population. These findings can be informative for policymakers to tackle vitamin D deficiency through food fortification strategy.