| 1. |
- Klingberg, Eva, et al.
(författare)
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Seasonal variations in serum 25-hydroxy vitamin D levels in a Swedish cohort
- 2015
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Ingår i: Endocrine. - : Springer Science and Business Media LLC. - 1355-008X .- 1559-0100. ; 49:3, s. 800-808
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Tidskriftsartikel (refereegranskat)abstract
- To study seasonal inter-individual and intra-individual variations in serum 25-hydroxy vitamin D (25(OH)D) and to explore parameters associated with 25(OH)D in a healthy Swedish adult population. 540 blood donors (60 % men; mean age 41 +/- A 13 years) and 75 thrombocyte donors (92 % men, aged 46 +/- A 11 years) were included. Serum was collected during 12 months and analyzed for 25(OH)D and parathyroid hormone (S-iPTH). The blood donors answered questionnaires concerning vitamin D supplements, smoking, physical activity, sunbed use and sun holidays. Repeated serum samples were collected from the thrombocyte donors to study the intra-individual variations in S-25(OH)D. S-25(OH)D varied greatly over the year correlating with the intensity of the UV-B irradiation (r (S) = 0.326; p < 0.001). During January-March, a S-25(OH)D level 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 was negatively correlated with body mass index and S-iPTH, but was significantly higher in holiday makers in sunny destinations, sunbed users, non-smokers, and in the physically active. The intra-individual analyses showed a mean increase in S-25(OH)D by 8 nmol/L/month between April and August. Approximately 75 % had serum 25(OH)D values < 75 nmol/L during 75 % of the year and 50 % had serum 25(OH)D < 50 nmol/L during 50 % of the year. Serum 25(OH)D was strongly associated with parameters related to sun exposure, but only weakly with intake of vitamin D supplements.
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| 2. |
- Klingberg, Eva, et al.
(författare)
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The vitamin D status in ankylosing spondylitis in relation to intestinal inflammation, disease activity, and bone health: a cross-sectional study
- 2016
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Ingår i: Osteoporosis International. - : Springer Science and Business Media LLC. - 0937-941X .- 1433-2965. ; 27:6, s. 2027-2033
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Tidskriftsartikel (refereegranskat)abstract
- We assessed the vitamin D status in ankylosing spondylitis (AS) patients and healthy controls in the late winter when no vitamin D is produced by the sunlight. The vitamin D status was often poor, but not lower in AS and not associated with disease activity or signs of gut inflammation. The aims of the study were to investigate the vitamin D levels attained mainly by dietary intake in ankylosing spondylitis (AS) in comparison with healthy controls and in relation to gut inflammation, measured indirectly by fecal calprotectin, disease activity, osteoproliferation, bone mineral density (BMD), and vertebral fractures. Serum 25-hydroxy vitamin D (25(OH)D) was measured in 203 AS patients and 120 healthy controls at the end of "the vitamin D winter," when the out-door UVB irradiation is too low to allow synthesis of vitamin D-3 in the skin at the latitude of Gothenburg, Sweden. Fecal calprotectin was measured in stool samples. Disease activity was assessed with CRP, ESR, ASDAS(CRP,) BASDAI, BAS-G, BASFI, and BASMI. Lateral spine radiographs were scored for osteoproliferation and vertebral fractures using the mSASSS and Genant scores. BMD was measured in the lumbar spine and femoral neck. Vitamin D insufficiency (a serum 25(OH)D < 50 nmol/L) was found in approximately 50 % of the AS patients, but serum 25(OH)D was not different from healthy controls and not significantly correlated with fecal calprotectin, gastrointestinal symptoms, disease activity parameters, mSASSS, BMD, or vertebral fractures. The vitamin D status was often poor in the late winter in AS but not different from the healthy controls. No evidence for a connection between subclinical gut inflammation, malabsorption, and hypovitaminosis D was found. Serum 25(OH)D was not associated with disease activity, osteoproliferation, BMD, or vertebral fractures. We suggest that the lower vitamin D levels in AS, previously found by others, may be caused by reduced out-door UVB exposure.
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| 3. |
- Oleröd, Göran, et al.
(författare)
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The variation in free 25-hydroxy vitamin D and vitamin D-binding protein with season and vitamin D status.
- 2017
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Ingår i: Endocrine connections. - 2049-3614. ; 6:2, s. 111-120
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Tidskriftsartikel (refereegranskat)abstract
- Serum 25-hydroxy vitamin D [25(OH)D] varies greatly with season at northern latitudes. The purpose of this study was to determine if the seasonal variations in serum total 25(OH)D are followed by a concomitant variation in free 25(OH)D or if the variation is damped by alterations in the binding capacity of DBP.Serum was collected from 540 healthy blood donors (60% men; mean age 41 ± 13 years) during 12 months and analyzed for total 25(OH)D, directly measured free 25(OH)D, vitamin D-binding protein (DBP) and albumin. Calculated free 25(OH)D was estimated.The UV-B radiation during the sampling month was positively correlated with the serum levels of total 25(OH)D (r = 0.355,P < 0.001), directly measured free (r = 0.336,P < 0.001) and calculated free 25(OH)D (r = 0.275,P < 0.001), but not with DBP and albumin. The percentage of free 25(OH)D was higher during the winter months than that during the summer months (0.020 ± 0.005% vs 0.019 ± 0.004%;P = 0.007) and higher in participants with a serum 25(OH)D below 25 nmol/L than that in participants with a serum 25(OH)D above 75 nmol/L (0.031 ± 0.007% vs 0.017 ± 0.003%;P < 0.001). iPTH was correlated with directly measured free 25(OH)D (r = -0.226;P < 0.001), but only weakly with calculated free 25(OH)D (r = -0.095;P = 0.027).Directly measured free serum 25(OH)D was highly correlated with total serum 25(OH)D and followed the same seasonal variation, whereas the serum concentrations of DBP and albumin were stable. The fluctuation in free 25(OH)D was only marginally damped with an increase in the percentage of free 25(OH)D during the winter months and in participants with vitamin D deficiency.
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