SERUM 25HYDROXYVITAMIN D BELOW 75 NMOL/L OBSERVED IN 75% OF HEALTHY SWEDISH ADULTS DURING 75% OF THE YEAR
Göran Oleröd1,*, Eva Klingberg2, Jan Konar1, Max Petzold 3, Ola Hammarsten1
1Department of Clinical Chemistry and Transfusion Medicine, 2Department of Rheumatology and Inflammation Research, 3Akademistatistik- Centre for Applied Biostatistics, Occupational and Environmental Medicine, University of Gothenburg, Sweden, Gothenburg, Sweden
Introduction: Numerous observational studies associate vitamin D insufficiency (VDI) with chronic illnesses.
There are two definitions of VDI; serum 25-hydroxyvitamin D (S-25(OH)D) <50nmol/L or <75nmol/L.
Objectives: To study the inter- and intra-individual variations in S-25(OH)D during different seasons of the year and to explore demographic and lifestyle related parameters associated with S-25(OH)D in healthy Swedish adults.
Methods: Blood donor serum was collected during 12 months and analyzed for 25(OH)D and parathyroid hormone (iPTH). The blood donors answered questionnaires concerning vitamin D supplements, smoking, physical activity, solarium use and sun holidays. To study the intra-individual variations in S-25(OH)D repeated samples were also collected from thrombocyte donors during a period from April to November.
Results: 540 blood donors (60% men; mean age 41±13 years) and 75 thrombocyte donors (92% men, aged 46±11 years) were included. S-25(OH)D varied greatly over the year correlating with the UV-B iirradiation intensity (rS=0.326;p<0.001).The mean S-25(OH)D was 73% higher in July (81.9±26.2 nmol/L) than in February (47.4±20.7 nmol/L;p<0.001) During Jan-Mars S-25(OH)D below the thresholds of 50 and 75 nmol/L was observed in 58% and 88% respectively and during July-September in 11% and 50% (p<0.001).
S-25(OH)D correlated negatively with BMI and iPTH, but was significantly higher in sun-holiday travellers, solarium-users, non-smokers and in the physically active.
The intra-individual analyses showed a mean increase in S-25(OH)D of 8 nmol/L/month between April to August.
Conclusion: Vitamin D insufficiency is common in the Swedish healthy adult population. Approximately 75% had S-25(OH)D values <75 nmol/L during the whole year and 50% had S-25(OH)D values <50 nmol/L during 50% of the year. S-25(OH)D was strongly associated with parameters related to sun exposure, but only weakly with intake of vitamin D supplements.
Keywords: Biochemistry, Skeletal muscle