No improvement in cardiovascular risk factors in overweight and obese subjects after supplementation with vitamin D3 for 1 year.
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 D(3)) 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.