Vitamin D-fortified foods improve wintertime vitamin D status in women of Danish and Pakistani origin living in Denmark: a randomized controlled trial
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Low vitamin D status is prevalent worldwide. We aim to investigate the effect of vitamin D fortification on serum 25-hydroxyvitamin D (25(OH)D) concentration in women of Danish and Pakistani origin at risk of vitamin D deficiency.
A 12-week randomized, double-blinded, placebo-controlled intervention trial during winter time, designed to provide 20 µg vitamin D3/day through fortified yoghurt, cheese, eggs and crisp bread, and assess the change in serum 25(OH)D. Participants were 143 women of Danish and Pakistani origin, living in Denmark, randomized into four groups, stratified by ethnicity.
Mean (SD) baseline 25(OH)D concentrations among women of Danish and Pakistani origin were 49.6 (18) and 46.9 (22) nmol/L, respectively (P = 0.4). While 9% of Danish women had 25(OH)D < 30 nmol/L, the prevalence among women of Pakistani origin was 24%. Median (IQR) vitamin D intake among Danish and Pakistani women at endpoint was 32.0 (27.0, 34.4) µg/day and 24.2 (19.2, 30.8) µg/day, respectively. Endpoint serum 25(OH)D increased in fortified groups to 77.8 (14) nmol/L among Danish women and 54.7 (18) nmol/L among women of Pakistani origin (P < 0.01). At endpoint, 0% in the Danish-fortified group and 3% in the Pakistani-fortified group had 25(OH)D < 30 nmol/L, compared with 23 % and 34% in their respective control groups.
Vitamin D fortification of four different foods for 12 weeks during winter was effective in increasing serum 25(OH)D and reducing the prevalence of very low vitamin D status among women of Danish and Pakistani origin.
ClinicalTrials.gov with identifier
KeywordsVitamin D Food-based RCT ODIN Women of Pakistani origin Women of Danish origin Fortified foods
Serum 25-hydroxyvitamin D
Randomized controlled trial
Food-based solutions for optimal vitamin D nutrition and health through the life cycle
Coefficient of variance ((SD/mean) × 100)
Tolerable upper intake level
Food frequency questionnaire
Towards a strategy for optimal vitamin D fortification
University College Cork
Liquid chromatography–tandem mass spectrometry
Vitamin D standardization program
Analysis of variance
Analysis of covariance
We thank the following individuals for their help and assistance with this trial: Majken Ege, Karin Hess Ygil, Dorte L Korsbech, Erika Baig for assisting with the measurements, dietary intake calculations and FFQ work, Bashy Quraishy, Raza Mustafa, Saima Raza, Shahnaz Qureshi and Shais Anais for introducing us to the Pakistani societies in Copenhagen, Denmark. We would also like to thank Dr. George Hull and Ms. Kirsten Dowling at University College Cork for their contribution to the analysis of serum 25(OH)D within the ODIN project. We thank our industrial partners FrieslandCampina, Hedegaard, Lantmännen Cerealia and DSM nutritional products for delivering the foods used in the trial.
IMG and RA collected the data, TC managed intake data, JJ analyzed the vitamin D content of the food, KC oversaw the analysis of serum 25(OH)D, IMG undertook the statistical analyses and wrote this paper. EWA assisted with the statistical analyses. RA, IT, KC and MK designed the study. All contributed to the manuscript.
This research was undertaken by the National Food Institute, Technical University of Denmark (DTU) and the study is a part of the European collaborative project “Food-based solutions for eradication of vitamin D deficiency and health promotion throughout the life cycle - ODIN”, which was funded by the European Commission (FP7/2007-2013) under grant agreement no. 613977 (ODIN) and by the National Food Institute, Technical University of Denmark. The cheese and yoghurt products were produced and provided free of charge by FrieslandCampina. The eggs were produced and provided free of cost by Hedegaard Agro, including chicken feed produced by Dava Foods, the crisp bread was produced by Smørum konditori (confectionary) with ingredients provided free of cost by Lantmännen cerialia and vitamin D3 supplied by DSM Nutritional Products.
Compliance with ethical standards
Written informed consent was obtained from all participants on enrolment. The study protocol was approved by the local ethical committee (protocol no. H-15008276) and registered at ClinicalTrials.gov with identifier: NCT02631629. The study was carried out in accordance with the Declaration of Helsinki.
Conflict of interest
None of the authors had conflicts of interest. The industry partners had no influence on the design of the study, the interpretation of the results or the writing of this manuscript.
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