Paradoxical suboptimal vitamin D levels in a Mediterranean area: a population-based study

Policies in sunny countries, such as those in the Mediterranean area, do not promote vitamin D supplementation despite some studies might suggest the high prevalence of sub-optimal levels. The objective was to determine the vitamin D levels by 25-hydroxyvitamin D (25(OH)D) of a Mediterranean population and their characteristics. This population-based study included a database of public health system from all individuals living in Catalonia > 18 years who had some measure of 25(OH)D between January 2018 and April 2021. More than half million people were classified based on 25(OH)D measurements to study their characteristics. Three vitamin D categories were created: < 20 ng/ml deficiency, 20–30 ng/ml insufficiency and > 30 ng/ml optimal. Less than 10% of the population residing in Catalonia had recent 25(OH)D determinations and the majority of determinations were in ≥ 45 years and in women. Around 80% of young people with determination had sub-optimal levels but the prevalence of vitamin D supplementation prescription increased with age which was associated with better values of 25(OH)D. In a Mediterranean area 25(OH)D determinations were low despite the high prevalence of suboptimal levels in the population with recent determination. In addition, the measurements were especially concentrated in people ≥ 45 years of age and in women who were, in addition, the groups to whom the most vitamin D supplementation was prescribed. On the contrary, young people presented few determinations of 25(OH)D and, although majority of them showed sub-optimal levels, vitamin D supplementation was not prescribed in most cases.