Background: Vitamin D is a secosteroid, a lipid-soluble vitamin that is involved in various physiological responses, including skeletal metabolism and immune response. Vitamin D 25(OH)D in the blood is also influenced by environmental factors, lifestyle, and is genetically determined. While there is abundant sunlight in every part of Saudi Arabia throughout the year, hypovitaminosis D is prevalent. The locally obtained reference interval has not yet been defined among the people of Alqurayyat. The study was conducted to identify population-specific serum 25(OH)D reference ranges among healthy adult Saudi men in Alqurayyat who do not receive vitamin D supplements. Materials and Methods: The study was a cross-sectional design conducted between December 2022 and August 2023. 204 apparently healthy Saudi men aged 18– 45 years were selected after eliminating statistical exceptions. Participants were taken from voluntary blood donors at Alqurayyat General Hospital. Serum 25(OH)D was measured by chemiluminescence immunoprecipitation assay done on the UniCel DxI 800 analyzer. The extreme values were also removed by the Tukey method. The reference range was derived using the 95% central distribution, which is the 2.5th and 97.5th percentiles. Results: The 25(OH)D mean was 12.47 ± 4.84 ng/mL (95% CI: 11.77– 13.17 ng/mL). The calculated reference interval was 4.22– 26.14 ng/mL, which is significantly lower than the international norms. Vitamin D was low in 93%, under 20 ng/mL, with 7% between 20– 29 ng/mL. None of the subjects had adequate levels (> 30 ng/mL). Conclusion: The high prevalence of vitamin D deficiency (93%) in this population of non-supplementing healthy adult men is one of the key health issues of the population. The calculated reference range is quite low compared to international standards, which probably shows local lifestyle and cultural conditions restricting productive sun exposure. More research and specific treatment are justified. Keywords: Vitamin D, 25-hydroxyvitamin D, 25(OH)D, healthy adults, vitamin D deficiency, reference range, Saudi Arabia
Aldaham et al. (Sun,) studied this question.