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Purpose: The serum 25-hydroxyvitamin D (25(OH)D) levels are lower in obese than lean subjects. The present study examines the cross-sectional and longitudinal relations between body mass index (BMI) and serum 25(OH)D, and the serum 25(OH)D response to vitamin D supplementation in relation to BMI., Methods: The Tromsø study is a longitudinal population-based multipurpose study. The fourth survey was conducted in 1994 and the sixth in 2008. The intervention study was a 1-year placebo-controlled randomized intervention trial, where the results from the 93 subjects given 40,000 IU per week are presented., Results: A total of 10,229 subjects were included in the 2008 cross-sectional study. There was a significant negative association between serum 25(OH)D levels and BMI which was also present during the winter months. Serum 25(OH)D levels varied through seasons, but not BMI. In the longitudinal study from 1994 to 2008 which included 2,656 subjects, change in BMI was a significant negative predictor of change in 25(OH)D. In the intervention study, there was a significant and negative correlation between BMI and serum 25(OH)D both at baseline and at the end of the study. The increase in serum 25(OH)D after 1 year was significantly and inversely related to baseline BMI., Conclusions: We have confirmed the strong association between serum 25(OH)D and BMI. The very obese need higher vitamin D doses than lean subjects to achieve the same serum 25(OH)D levels.

Objective: Because we found higher serum 25-hydroxyvitamin D (25(OH)D) levels among smokers than among non-smokers with analyses using an electrochemiluminescence immunoassay (ECLIA) from Roche, the purpose of the present study was to examine whether this difference between smokers and non-smokers was maintained using other serum 25(OH)D assays., Design: A cross-sectional population-based study on 6932 participants from the Tromsø study, 1994-1995, and one validation study comparing six different serum 25(OH)D assays in 53 non-smokers and 54 smokers were performed., Methods: The association between smoking, season and serum 25(OH)D as measured by ECLIA (Roche) was assessed in the population-based study using general linear models with multivariate adjustments. In the validation study, serum levels of 25(OH)D were analysed with liquid chromatography coupled with mass spectrometry assay from two different laboratories, RIA (DiaSorin), HPLC, RIA (IDS) and ECLIA (Roche). T-tests and linear mixed model analyses were performed to compare the serum 25(OH)D levels in smokers and non-smokers within and between the methods., Results: In the population-based study, the serum levels of 25(OH)D using the ECLIA method were 51.9, 53.2 and 72.0 nmol/l in never, former and current smokers (P<0.01). In the validation study, the serum concentration of 25(OH)D was 10.3 nmol/l higher in smokers than in non-smokers (P<0.01) using the ECLIA (Roche), while non-significantly lower serum levels of 25(OH)D were found in smokers using the other five methods., Conclusions: These two studies indicate that the ECLIA (Roche) overestimates serum 25(OH)D levels in smokers by unknown mechanisms. If confirmed, this might have clinical consequences, and the issue needs further exploration.

Introduction: In vitro studies indicate an anticoagulant effect of 1,25-dihydroxyvitamin D, and sun exposure may lower the risk of thrombotic events. Accordingly, an effect on haemostatic parameters could be expected after supplementation with vitamin D., Materials and Methods: 158 obese or overweight subjects were included in a one year intervention study with supplementation with 40.000 IU vitamin D(3) per week or placebo. All subjects were given 500 mg calcium daily. Plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator antigen (tPA Ag), and tissue factor-induced thrombin generation over time in plasma assessed by the calibrated automated thrombogram (CAT) method as a parameter of over all thrombotic activity, were measured before and at the end of the study., Results: Mean baseline serum 25(OH)D level was 61.8 nmol/L and increased in the vitamin D group to 145.6 nmol/L at the end of the study. At baseline there was a significant decrease in the CAT variables lag time and time to peak of the thrombogram across increasing serum 25(OH)D quartiles, whereas no significant associations between serum 25(OH)D and PAI-1 or tPA Ag were found. After one year, no significant differences were found between the vitamin D and placebo groups regarding change in any of the haemostatic parameters., Conclusions: The association between lag time and time to peak in the CAT assay and serum 25(OH)D levels could indicate a pro-thrombotic state in subjects with high serum 25(OH)D levels, whereas the lack of effect of high dose vitamin D supplementation questions the causality of this relation., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Low serum 25-hydroxyvitamin D (25(OH)D) levels are associated with risk factors for cardiovascular disease, and they also appear to predict later development of type 2 diabetes, cancer, and an increased mortality rate. These predictions are all based on a single 25(OH)D measurement, but so far there are no known reports on tracking of serum 25(OH)D levels. In the present Norwegian study, serum 25(OH)D levels were measured 1) in 2,668 subjects in the 1994 and 2008 Tromsø surveys and 2) every third month for 1 year in 94 subjects randomly assigned to placebo in a vitamin D intervention study. There was a marked seasonal variation in 25(OH)D, and, depending on the method of adjusting for season, the correlation coefficient between serum 25(OH)D measurements from 1994 and 2008 ranged from 0.42 to 0.52. In the 1-year intervention study, the correlation between baseline and 12-month values was 0.80. Apart from the effect of season, changes in weight, intake of vitamin D, and physical activity were related to change in serum 25(OH)D levels. Tracking of serum 25(OH)D appears similar to that for blood pressure and serum lipids, and it provides some support for the use of a single 25(OH)D measurement to predict future health outcomes.

Objectives: The objective of the present study was to examine the cross-sectional relation between serum 25-hydroxyvitamin D [25-(OH) D] levels and depression in overweight and obese subjects and to assess the effect of vitamin D supplementation on depressive symptoms., Design: Cross-sectional study and randomized double blind controlled trial of 20,000 or 40,000 IU vitamin D per week versus placebo for 1 year., Setting: A total of 441 subjects (body mass index 28-47 kg m(-2), 159 men and 282 women, aged 21-70 years) recruited by advertisements or from the out-patient clinic at the University Hospital of North Norway., Main Outcome Measures: Beck Depression Inventory (BDI) score with subscales 1-13 and 14-21., Results: Subjects with serum 25(OH)D levels < 40 nmol L(-1) scored significantly higher (more depressive traits) than those with serum 25(OH)D levels > or = 40 nmol L(-1) on the BDI total [6.0 (0-23) versus 4.5 (0-28) (median and range)] and the BDI subscale 1-13 [2.0 (0-15) versus 1.0 (0-29.5)] (P < 0.05). In the two groups given vitamin D, but not in the placebo group, there was a significant improvement in BDI scores after 1 year. There was a significant decrease in serum parathyroid hormone in the two vitamin D groups without a concomitant increase in serum calcium., Conclusions: It appears to be a relation between serum levels of 25(OH)D and symptoms of depression. Supplementation with high doses of vitamin D seems to ameliorate these symptoms indicating a possible causal relationship.

Jorde R, Sneve M, Torjesen P, Figenschau Y (University of Tromsø, Tromsø; Medical Clinic University Hospital of North Norway, Tromsø; University Hospital of North Norway, Tromsø; Aker University Hospital, Oslo; University Hospital of North Norway, Tromsø; and University of Tromsø, Tromsø; Norway). No improvement in cardiovascular risk factors in overweight and obese subjects after supplementation with vitamin D3 for 1 year. J Intern Med 2010; 267:462–472. Background and Aim. Cross-sectional studies indicate vitamin D to be of importance for glucose tolerance, blood pressure and serum lipids, but whether supplementation with vitamin D would improve cardio-vascular risk factors is not known. Design and Setting. The study was a 1 year, double blind placebo-controlled intervention trial performed at the University Hospital of North Norway from November 2005 to October 2007. Subjects. A total of 438 overweight or obese subjects, 21–70 years old, were included and 330 completed the study. Interventions. The subjects were randomized to vitamin D (cholecalciferol, vitamin D3) 40 000 IU per week (DD group), vitamin D 20 000 IU per week (DP group), or placebo (PP group). All subjects were given 500 mg calcium daily. Main Outcome Measures. Fasting serum lipids and blood pressure were measured and an oral glucose tolerance test performed at start and end of the study. Results. At baseline the mean serum 25(OH)D levels were 58 nmol L−1 (all subjects) and increased to 140 and 101 nmol L−1 in the DD and DP groups, respectively. No significant differences were found between the three groups regarding change in measures of glucose metabolism or serum lipids. In the DP group, there was a slight but significant increase in systolic blood pressure compared with the placebo group. Conclusions. Our results do not support a positive effect of vitamin D on glucose tolerance, blood pressure or serum lipids. Further studies in subjects with low serum 25(OH)D levels combined with impaired glucose tolerance, hypertension or dyslipidaemia are needed. [ABSTRACT FROM AUTHOR]

The objective of the present study was to examine the cross-sectional relation between serum 25-hydoxyvitamin D (25(OH)D) levels and depression in obese subjects, and to assess the effect of vitamin D supplementation on depressive symptoms. 441 subjects (body mass index 28 - 47 kg/m2, 159 men and 282 women, aged 21 - 70 years) were recruited by advertisements or from the out-patient clinic at the University Hospital of North Norway, and in a double blind controlled trial randomized to 20.000 or 40.000 IU vitamin D per week versus placebo for 1 year. Subjects with serum 25(OH)D levels < 40 nmol/L scored significantly higher (more depressive traits) than those with serum 25(OH)D levels ≥ 40 nmol/L on the Beck Depression Inventory (BDI) total (6.0 (0 - 23) versus 4.5 (0 - 28) (median and range)) and the BDI subscale 1 - 13 (2.0 (0 - 15) versus 1.0 (0 - 29.5)) (P < 0.05). In the two groups given vitamin D, but not in the placebo group, there was a significant improvement in BDI scores after one year. There was a significant decrease in serum parathyroid hormone in the two vitamin D groups, without a concomitant increase in serum calcium. It appears to be a relation between serum levels of 25(OH)D and symptoms of depression. Supplementation with high doses of vitamin D seems to ameliorate these symptoms, indicating a possible causal relationship. [Copyright &y& Elsevier]