Objective: To assess the impact of national fortification of fluid milks and margarines with vitamin D on dietary intake and on serum 25-hydroxyvitamin D concentration in Finnish 4-year-old children.
Design, subjects and methods: Two cohorts of children were studied during wintertime, one before (n=82) in 2001-2002 and the other after (n=36) the initiation of fortification in 2003-2004. Dietary intake was estimated by 4-day food records and serum 25-hydroxyvitamin D concentration was analyzed by radioimmunoassay.
Results: The mean intake of vitamin D was higher the after initiation of fortification (mean (95% confidence interval (CI)); 4.5 (3.8-5.1) microg) than before it (2.1 (95% CI 1.8-2.3) microg; P<0.001), although there were no differences in consumption of the main food sources of vitamin D between the two cohorts. The difference between the cohorts was also evident when the intake of vitamin D was adjusted for energy intake (0.78 (95% CI 0.70-0.90) and 0.37 (95% CI 0.32-0.42) microg/MJ after and before fortification, respectively, P<0.001). After fortification, the mean intake approached that recommended, but was achieved by only 30.6% of the children. Equally, the serum 25-hydroxyvitamin D concentration was higher after fortification (64.9 (95% CI 59.7-70.1) nmol/l) compared to prior it (54.7 (95% CI 51.0-58.4) nmol/l; P=0.002).
Conclusions: The results indicate that the national fortification of fluid milks and margarines with vitamin D safely improved the vitamin D status of children. This approach, in view of the novel health effects beyond bone metabolism, encourages fortification of new food sources with vitamin D or use of vitamin D supplements particularly during wintertime.