In fact, about 47.6% had vitD deficiency with an approximate daily vitD intake under 200UI/daily. Although Tunisia is a sunny country, sun exposure was reported to be insufficient and dietary vitD intake did not achieve the dietary reference intakes. The spectrum of vitD status across the population in Tunisia resembles that in Southern European countries rather than in Middle Eastern ones. The global prevalence of hypovitaminosis D appears to be increasing, and it is estimated that more than 1.5 billion people worldwide have vitD deficiency including healthy community-living people, and even patients receiving medical treatment for osteoporosis, which makes this disorder one of the most common nutritional deficiencies in the world affecting all segments of the population. Given the pleiotropic effects of vitD, the scientific focus has gone beyond its known classic benefits on skeletal health to include multiple pathologies such as hyperglycemic disorders, cardiovascular, neurological and liver diseases. In recent years, research articles investigating associations between vitD status and health have reached an all-time high, and an increase in supplementation studies has followed. Vitamin D (vitD) is a fat soluble secosteroid vitamin with multiple functions extending beyond the regulation of intestinal calcium absorption. Taking into account these variations can help to better adapt vitD intake to ensure a higher response to supplementation. ConclusionsĭBP-rs4588, CYP2R1-rs10766197 and rs12794714 variants are associated with variations in serum 25(OH)D concentrations and efficacy of response to vitD supplementation in Tunisian adults. There was a significant linear negative correlation between baseline 25(OH)D and post supplementation 25(OH)D concentration ( r = −0.437 p < 0.001) as well as a linear negative association between the increase in 25(OH)D concentration and GRS (GRS: genetic risk score = the sum of risk alleles) ( r = −0.149 p = 0.033). These three SNPs contributed in 18.8% in response variability with rs4588 being the most influential (10.3%). Statistical study was carried out with SPSS23.0.

Genetic study was performed by PCR-RFLP for 15 single nucleotide polymorphisms (SNPs) belonging to DBP, CYP2R1, CYP27B14, CYP24A1 and VDR genes. After giving an informed consent, all participants were asked to complete a generalized questionnaire and to follow a detailed personalized supplementation protocol. In total, 245 healthy participants were recruited from occupational medicine service in Sahloul University Hospital with vitD deficiency. The aim of this study was to determine the influence of polymorphisms in some key gene actors of the vitamin D (vitD) metabolic pathway on supplementation efficacy.

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