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Background: Low vitamin D status is especially prevalent in countries of northern latitudes. Notably, many immigrants living in Denmark, and other Nordic countries, are at a higher risk of vitamin D deficiency compared to the native residents. Low vitamin D status has been linked with adverse bone health outcomes and decreased muscle strength. Food-based strategies aiming at improving vitamin D intake and status across the population, such as vitamin D food fortification may be a suitable solution. Data on the effects and safety of a food-based approach, especially in at-risk population subgroups, is lacking.

Aim: The overall aim of this project was to study the effect and safety of food based solutions to prevent vitamin D deficiency in high risk populations of women of Caucasian and south Asian origin living in Denmark. Additionally, we assessed the effect of the intervention on the bone markers osteocalcin (OC), Bone specific Alkaline Phosphatase (BALP), Procollagen type 1 amino-terminal propeptide (P1NP), C-terminal crosslinked telopeptide of type 1 collagen (CTX), and on muscle strength measured by hand grip strength, knee extension strength and a 30-second chair stand test.
Design and methods: A three-month randomised double-blinded, placebo-controlled trial. The subjects in the intervention groups were given four different fortified foods (cheese, yoghurt, eggs, crisp-bread) contributing with ≈ 30 µg/day of vitamin D3, while the placebo groups received equivalent foods not fortified with vitamin D. The main endpoint was the change in serum 25(OH)D concentration (Paper II). Secondary endpoints were muscle strength, markers of bone turnover (Paper III). Prior to the recruitment of study participants a fortification model was prepared (Paper I).
Results: In the fortification modelling we found that adequate and safe levels of intake were present in all the Danish women (n = 855) in the scenarios in which fortified foods (20 µg/dag) and a daily supplement of vitamin D up to 40 μg/day were added to the habitual diet (Paper I). A total of 143 women of Danish and Pakistani origin were enrolled in the ODIN FOOD study. The baseline serum 25(OH)D was 49.6 (18) nmol/L and 46.9 (22) nmol/L among women of Danish and Pakistani origin, respectively. The prevalence of serum 25(OH)D < 30 nmol/L and < 50 nmol/L was 9 and 50 % of the women of Danish origin and 24 and 32 % of the women of Pakistani origin, respectively. Following the intervention mean (standard deviation) endpoint serum 25(OH)D concentration in the fortified food groups were 77.8 (15) nmol/L and 54.7 (18) nmol/L among the women of Danish origin and Pakistani origin, respectively. At endpoint the prevalence of 25(OH)D concentration < 30 nmol/L in the Danish fortified group and Pakistani fortified group were 0 % and 3 %, respectively, compared with 7 % and 11 % in their respective control groups. The increase in serum 25(OH)D concentration following the intervention, among the of the participants receiving fortified foods, was dependent on the, baseline serum 25(OH)D concentration, ethnicity and to a lesser degree BMI. Compliance with the fortified foods was significantly higher among the women of Danish origin compared to women of Pakistani origin (Paper II).The bone formation marker osteocalcin (OC) were significantly higher among the women of Danish origin at baseline, compared to women of Pakistani origin. The intervention did not result in significant changes of the bone turnover markers OC, Bone specific Alkaline Phosphatase (BALP), Procollagen type 1 amino-terminal propeptide (P1NP), C-terminal crosslinked telopeptide of type 1 collagen (CTX). Baseline handgrip and knee extension strength were 4.8 and 6.3 kg higher among participants of Danish origin compared to participants of Pakistani origin. Fortification with vitamin D did not have an effect on the muscle strength measured as hand grip strength in a linear model. Analysis of the knee extension strength showed an approximately 2 kg higher increase among the women of Danish origin compared to women of Pakistani origin, when adjusting for intervention group, BMI and baseline knee strength (Paper III).
Conclusion: By performing modelling of vitamin D fortification in the population of Danish women 18–50 years, we showed that adequate and safe levels of intake were present in scenarios including low dose fortification of several foods and vitamin D supplement intake below 40 μg/day.
In the ODIN FOOD intervention study we found that vitamin D fortification of 30 µg/day, provided in four different foods, for 12 weeks during winter was effective in increasing vitamin D status and reducing the prevalence of vitamin D deficiency among women of Danish and Pakistani origin. Compliance to the fortified foods was higher among the women of Danish origin compared to women of Pakistani origin. Following the intervention no significant changes of the bone turnover markers osteocalcin, BALP, P1NP and CTX were found. Muscle strength measured as hand grip strength and chair-stand test did not change significantly following the intervention. However, the change in knee extension strength following intervention showed a tendency to be higher among the participants of Danish origin compared to participants of Pakistani origin.
Original languageEnglish
Place of PublicationKgs. Lyngby, Denmark
PublisherTechnical University of Denmark
Number of pages97
Publication statusPublished - 2018

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