Purpose of this study is to investigate the effect of treatment with vitamin D3 (cholecalciferol) compared with placebo in a trial including chronic kidney disease patients with vitamin D deficiency.

Most patients with chronic renal insufficiency have vitamin D deficiency. It is still not common practice among nephrologists to monitor and correct vitamin D deficiency of chronic kidney disease (CKD) patients, because it is widely believed that any vitamin D deficiency associated with calcium-phosphate disturbances is better treated with activated vitamin D.

However, correction of vitamin D deficiency with native vitamin D seems to have numerous favorable effects not only related to the renal and intestinal handling of calcium and phosphate. It may have beneficial effects on bone and vascular health, the immune system and physical performance that are not obtained with active vitamin D treatment.

We are therefore planning a randomized, placebo-controlled, intervention study of 8 weeks' duration in which vitamin D3 supplementation (40 000 IE per week in one capsule) is compared with placebo in a trial including 120 CKD patients with vitamin D deficiency. Multiple biological variables are monitored in order to assess any effect on the biological systems of interest.

Inclusion Criteria:

• Chronic kidney disease (CKD 3-5 amd renal transplanted patients)
• Age > 18 years
• Vitamin D insufficiency or deficiency (25-OHD < 50 nmol/l, 3 months before project start)

Exclusion Criteria:

• Treatment with vitamin D2/D3 (dose more than 10000 IU within the last 3 months)
• Hypercalcaemia (ca++ > 1,35 mmol/l more than 4 weeks despite missing intake of calcium containing preparations and activated vitamin D)
• Uncontrolled hyperphosphataemia (s-phosphate > 2,2 mmol/l)
• Sarcoidosis
• Malignant disease
• Psychotic disorders
• Pregnancy and lactation women
• Allergy to soya and peanut