The aim of this study is to investigate the bioavailability of vitamin D2 and D3 as measured by the increase of the specific hydroxy forms in serum (25(OH)D2 and 25(OH)D3, respectively, and by total 25(OH)D.

Study design: Human volunteers will receive supplements containing either vitamin D2 or D3 for a period of 8 weeks. At baseline, after 4 weeks and after 8 weeks, 25(OH)D2, 25(OH)D3 and total 25(OH)D will be measured in serum as the main outcome variables. Additional outcome variables are the Ca concentration in serum, PTH concentration in serum, ambulatory blood pressure and heart rate, and renin expression in peripheral mononuclear cells.

Groups/Cohorts Assigned Interventions

1. Placebo group
2. Vitamin D2-group Daily treatment with vitamin d2-supplements (containing 2000 IU per capsule)
3. Vitamin D3-group Daily treatment with vitamin d3-supplements (containing 2000 IU per capsule)

Inclusion Criteria:

• 18 years
• healthy

Exclusion Criteria:

• supplementation of vitamin d and calcium
• hypercalcemia
• hypercalciuria
• chronical illness (diabetes, kidney diseases, cardiovascular diseases)
• serum-creatinine above 115 mmol/l
• pregnancy or breastfeeding women