Individual participant data (IPD)-level meta-analysis of randomised controlled trials with vitamin D-fortified foods to estimate Dietary Reference Values for vitamin D.

CONTEXT AND PURPOSE: Individual participant data-level meta-regression (IPD) analysis is superior to meta-regression based on aggregate data in determining Dietary Reference Values (DRV) for vitamin D. Using data from randomized controlled trials (RCTs) with vitamin D3-fortified foods, we undertook an IPD analysis of the response of winter serum 25-hydroxyvitamin (25(OH)D) to total vitamin D intake among children and adults and derived DRV for vitamin D. METHODS: IPD analysis using data from 1429 participants (ages 2-89 years) in 11 RCTs with vitamin D-fortified foods identified via a systematic review and predefined eligibility criteria. Outcome measures were vitamin D DRV estimates across a range of serum 25(OH)D thresholds using unadjusted and adjusted models. RESULTS: Our IPD-derived estimates of vitamin D intakes required to maintain 97.5% of winter 25(OH)D concentrations ≥ 25 and ≥ 30 nmol/L are 6 and 12 µg/day, respectively (unadjusted model). The intake estimates to maintain 90%, 95% and 97.5% of concentrations ≥ 50 nmol/L are 33.4, 57.5 and 92.3 µg/day, respectively (unadjusted) and 17.0, 28.1 and 43.6 µg/day, respectively (adjusted for mean values for baseline serum 25(OH)D, age and BMI). CONCLUSIONS: IPD-derived vitamin D intakes required to maintain 90%, 95% and 97.5% of winter 25(OH)D concentrations ≥ 50 nmol/L are much higher than those derived from standard meta-regression based on aggregate data, due to the inability of the latter to capture between person-variability. Our IPD provides further evidence that using food-based approaches to achieve an intake of 12 µg/day could prevent vitamin D deficiency (i.e., serum 25(OH)D < 30 nmol/L) in the general population.

No improvement in vitamin D status in German infants and adolescents between 2009 and 2014 despite public recommendations to increase vitamin D intake in 2012.

PURPOSE: Vitamin D is a key component for the growth and development of children and adolescents, influencing a multitude of functions. Worldwide epidemiological studies have shown that minimum vitamin D blood levels of ≥ 20.0 ng/ml, often defined as vitamin D sufficiency by international and national nutrition and pediatric organizations, are often not met in practice. In 2012 the D-A-CH (Germany, Austria, Switzerland) nutrition societies increased their vitamin D intake recommendations fourfold from 200 IU (5 µg) to 800 IU (20 µg) per day. The outcome of this study will contribute to answering the question as to whether the new recommendations for increased vitamin D intake improve the highly prevalent vitamin D deficiency status in German children and adolescents. METHODS: For this 6-year study (January 2009-December 2014) carried out in Mülheim an der Ruhr, Germany, healthy children and adolescents (n = 1929, age range 1-17 years, median age 11.0 years, 46.9% female) consulting a pediatric group practice (KIDS4.0) were recruited. Serum 25(OH)D determinations were performed using a competitive chemoluminescence immunoassay (CLIA, DiaSorin). RESULTS: The median serum vitamin D values for each year from 2009 to 2014 were 18.4, 13.0, 20.8, 16.4, 19.4 and 14.9 ng/ml. The summarized median 25(OH)D serum concentrations between the two time periods 2009-2012 and 2013-2014 after increasing recommendations for vitamin D intake did not show a significant difference (17.0 versus 16.8 ng/ml). CONCLUSIONS: The increased D-A-CH recommendations for vitamin D intake had no influence on vitamin D levels in children and adolescents. The prevalence of vitamin D deficiency has not changed compared to previous studies.

Vitamin D fortification of growing up milk prevents decrease of serum 25-hydroxyvitamin D concentrations during winter: a clinical intervention study in Germany.

Vitamin D plays an important role in human health. Current recommendations for vitamin D intake and endogenous supply through sun exposure are not met in German pre-school children, and suboptimal serum 25-hydroxyvitamin D concentrations, especially during the winter months, are common. Consequently, vitamin D supplementation or fortification have gained increased acceptance. The KiMi trial (Kindermilch=growing up milk) was a prospective, randomized, and double-blind study in which young children (2-6 years of age, n=92) were assigned to receive either vitamin D-fortified growing up milk (2.85 µg/100 ml) or semi skimmed cow's milk without added vitamin D. Daily consumption of fortified growing up milk contributed to the prevention of an otherwise frequently observed decrease in serum 25-hydroxyvitamin D concentration during winter (before winter: median 21.5 ng/mL (10.1-43.0 ng/mL) intervention vs. median 18.4 ng/mL (11.0-44.9 ng/mL) control; after winter: median 24.8 ng/mL (7.0-48.2 ng/mL) intervention vs. median 13.6 ng/mL (7.0-36.8 ng/mL) control) and proved to be safe during summer (median 27.6 ng/mL (18.8-40.5 ng/mL) intervention vs. median 27.4 ng/mL (17.8-38.7 ng/mL) control). Due to the high prevalence of vitamin D deficiency, fortification of growing up milk with vitamin D at a level used in this study could be an effective measure to improve vitamin D status.