A Systematic Review of Vitamin D Status and Dietary Intake in Various Slovenian Populations

AIM

Vitamin D (VitD) is involved in calcium and phosphate homeostasis, bone health, and normal functioning of the immune system. VitD status is monitored using serum 25-hydroxy-vitamin D (25(OH)D) as a biomarker. Serum 25(OH)D concentrations below 30 nmol/L indicate VitD deficiency and below 50 nmol/L indicate insufficiency. VitD can be synthesised endogenously in human skin when exposed to ultraviolet B (UVB) radiation. In the absence of sufficient UVB-light exposure, VitD intake becomes the main source of VitD, with a recommended daily intake of 20 μg. The aim of this study was to conduct a review and meta-analysis on the abovementioned topics, focusing on scientific studies in various Slovenian populations.

METHODS

We conducted a systematic review and meta-analysis of published scientific papers, academic theses, or conference contributions reporting serum 25(OH)D status and VitD intake across various Slovenian populations. A search was carried out using Web of Science, Scopus, Medline, and the Slovenian library database.

RESULTS

We identified 43 pertinent studies that addressed 25(OH)D status and 16 that addressed VitD intake. Serum 25(OH)D status was generally low across all populations, and notable seasonal variability was observed. VitD intakes were below 5 μg in all studies.

CONCLUSIONS

A general observation is that various population groups across Slovenia are at high risk of vitamin D insufficiency and deficiency, particularly during wintertime. Regarding vitamin D intake, all included studies reported daily intakes below the recommended level. We also identified key research gaps that need to be addressed to support further public health decision-making.

Vitamin D Intake in Slovenian Adolescents, Adults, and the Elderly Population

Vitamin D is involved in calcium and phosphorus metabolism, and is vital for numerous bodily functions. In the absence of sufficient UV-B light-induced skin biosynthesis, dietary intake becomes the most important source of vitamin D. In the absence of biosynthesis, the recommended dietary vitamin D intake is 10-20 µg/day. Major contributors to dietary vitamin D intake are the few foods naturally containing vitamin D (i.e., fish), enriched foods, and supplements. The present study aimed to estimate the vitamin D intake in Slovenia, to identify food groups that notably contribute to vitamin D intake, and to predict the effects of hypothetical mandatory milk fortification. This study was conducted using data collected by the national cross-sectional food consumption survey (SI.Menu) in adolescents (n = 468; 10-17 years), adults (n = 364; 18-64 years), and the elderly (n = 416; 65-74 years). Data collection was carried out between March 2017 and April 2018 using the EU Menu Methodology, which included two 24-h recalls, and a food propensity questionnaire. Very low vitamin D intakes were found; many did not even meet the threshold for very low vitamin D intake (2.5 µg/day). Mean daily vitamin D intake was 2.7, 2.9, and 2.5 µg in adolescents, adults, and the elderly, respectively. Daily energy intake was found to be a significant predictor of vitamin D intake in all population groups. In adolescents and adults, sex was also found to be a significant predictor, with higher vitamin D intake in males. The study results explained the previously reported high prevalence of vitamin D deficiency in Slovenia. An efficient policy approach is required to address the risk of vitamin D deficiency, particularly in vulnerable populations.