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Background: Previous studies have reported a high frequency of vitamin D deficiency (VDD) among different age groups in Iran., Aims: In this study, the current coverage, status of vitamin D supplement taking, and program efficacy have been evaluated by the Office of Nutrition Department Society in Iran since 2014., Methods: This study was conducted in collaboration with the International UNESCO center for Health-Related Basic Sciences and Human Nutrition and the Office of Nutrition Department Society. Sixty three medical universities were included in the current study to calculate the availability, accessibility and acceptability coverages. Furthermore, 3 medical universities including Mashhad (MUMS), Qom (QUMS) and Zahedan (ZAUMS) University of Medical Sciences were selected based on the results of the National Integrated Micronutrient Survey 2012 (NIMS-II study), in order to assess the status of vitamin D supplement intake in all age ranges., Results: Quantitative analysis showed that availability coverage was 74.96% and 77.56% and accessibility was 80.70% and 83.26% in elderly and middle-aged subjects, respectively in 2018. The acceptability was approximately 43.7% and 43.9% among elderly and middle-aged participants, respectively. The availability and acceptability coverage was 80.99% and 85.0% among students in high schools. The mean vitamin D supplement uptake frequency was 27.0% (n = 387); 20.7% and 29.2% in rural and urban area, respectively (P = 0.001). The results showed that there was no significant difference in serum vitamin D levels between urban (20.41 ± 6.43 ng/ml) and rural areas, (P = 0.887). There was no significant difference in the serum vitamin D concentrations between men and women (P = 0.461)., Conclusions: The frequency of taking vitamin D supplements was 27.0% in Iran in 2018. The frequency of taking of vitamin D supplements among vitamin D deficient group (serum vitamin D levels <19.99 ng/ml) was 43.6%. Lack of knowledge was the most important reason for not taking vitamin D supplement. Moreover, the serum vitamin D levels have increased in subjects aged 18-30 years old after the implementation of the vitamin D supplementary program., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2023 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.)

Background: Globally, about 1 billion people have inadequate levels of serum vitamin D and it is prevalent in all ethnicities and age groups. Few foods naturally contain sufficient vitamin D; therefore, most people get their requirements through supplementation. Hence vitamin D status is affected by genetic and environmental determinants including season of measurement, diet habitual, health status, body mass index and concurrent medication. Further studies are necessary to understand how genetic variation influences vitamin D metabolism. We aimed to explore the association between a potential vitamin D-related polymorphism (the rs10766197 polymorphism in the CYP2R1 gene) with the response to supplementation of vitamin D in 253 healthy Iranian girls., Material and Method: A total of 253 healthy subjects received 50,000 IU of vitamin D3 weekly for 9 weeks. Serum 25(OH)D concentrations and metabolic profiles were measured at baseline and after 9 weeks of supplementation. The genotypes of the CYP2R1 variant (rs10766197) were identified using TaqMan genotyping assays., Results: Serum 25(OH)D during the supplementation, increased in all individuals. Subjects with a AA major genotype at this locus had higher vitamin D concentrations after intervention (Changes (%) 448.4% ± 425% in AA vs 382.7% ± 301% in GG). This genetic variant modulated the response to supplementation (p < 0.001 and p-value SNP = 0.05). Regression analysis showed that the probability of affecting serum 25(OH)D, in individuals who had homozygous major allele GG was two-fold higher than carriers of the uncommon allele A (OR = 2.1 (1-4.2); p = 0.03). Interestingly, the Hs-CRP was reduced in AA carries while was elevated in individuals with GG and AG genotypes, after high-dose vitamin D supplementation., Conclusion: Changes in serum vitamin D and metabolic profile following high dose supplementation with vitamin D were associated with CYP2R1 polymorphism. Although carriers of the common G allele showed a greater response in the serum vitamin D., (Copyright © 2018 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

The global prevalence of vitamin D deficiency appears to be increasing, and the impact of this on human health is important because of the association of vitamin D insufficiency with increased risk of osteoporosis, cardiovascular disease and some cancers. There are few studies on the genetic factors that can influence vitamin D levels. In particular, the data from twin and family-based studies have reported that circulating vitamin D concentrations are partially determined by genetic factors. Moreover, it has been shown that genetic variants (e.g., mutation) and alteration (e.g., deletion, amplification, inversion) in genes involved in the metabolism, catabolism, transport, or binding of vitamin D to it receptor, might affect vitamin D level. However, the underlying genetic determinants of plasma 25-hydroxyvitamin D3 [25(OH)D] concentrations remain to be elucidated. Furthermore, the association between epigenetic modifications such as DNA methylation and vitamin D level has now been reported in several studies. The aim of current review was to provide an overview of the possible value of loci associated to vitamin D metabolism, catabolism, and transport as well epigenetic modification and environmental factors influencing vitamin D status., (© 2017 Wiley Periodicals, Inc.)