Vitamin D AND Glucose Handling Evaluated by Glucose Clamp

Vitamin D AND Cardiovascular Disease

In this study the investigators want to compare glucose handling (insulin secretion and insulin sensitivity) in 100 persons with low and 50 persons with normal-high levels of vitamin D, using a hyperglycemic clamp technique, were sugar is given intravenously for 3 hours in order to keep the blood sugar level at 10 mmol/L. Those with low vitamin D levels will be randomized to treatment with vitamin D3 (cholecalciferol) 40 000 IU/week or placebo for 6 months before a new clamp is performed.

The study hypothesis is that persons with low vitamin D levels have impaired glucose handling which might be improved by vitamin D supplementation.

Inclusion Criteria:

• generally: Subjects are recruited from the 6th Tromsø Study
• cases: serum 25-hydroxyvitamin D-levels below the 10 percentile; low levels confirmed with new serum analyses.
• controls: serum 25-hydroxyvitamin D levels 80-95 percentile, normal-high levels confirmed with new serum analyses.

Exclusion Criteria:

• diabetes
• myocardial infarction or apoplexia
• active cancer during last 5 years
• history of kidney stone
• pregnancy or premenopausal without safe anticonception
• primary hyperparathyroidism
• systolic blood pressure >175 or diastolic blood pressure >105