Several studies have shown that bone mineral density (BMD) at the femoral neck decreases with increasing physical handicap (EDSS-score) in MS patients. Possible explanations are less weightbearing exercise or less UV-exposure resulting in reduced vitamin D generation in the skin. Prevention of osteoporosis is a high priority, because treatment of the established disease remains sub-optimal.

We have designed a double-blind randomised controlled trial of two years' duration including 90-100 persons with MS age 18-50 to assess whether supplementation with vitamin D, given as a weekly dose of 20,000 IU cholecalciferol, can prevent bone loss.

The primary objective of this study is to determine changes in BMD over the 2 year study period comparing treatment and placebo groups.

The most important secondary objective is to determine cytokine profiles in blood samples. We will also assess parameters related to vitamin D status and physical performance.

Inclusion Criteria:

• Age 18 to 50 years
• EDSS < 4.0 (able to walk without rest some 500 m)
• Women have to be premenopausal
• MS according to the McDonald criteria; prepared and considered able to follow the protocol; using appropriate contraceptive methods (women of childbearing potential)
• Having given written informed consent.

Exclusion Criteria:

• Pregnancy or unwillingness to use contraception; alcohol or drug abuse
• Use of glucocorticoid treatment other than intravenous methylprednisolone for treatment of relapses
• Known allergy to cholecalciferol or arachis oil (peanuts)
• Therapy with digitalis, calcitonin, active vitamin D3 analogues, fluoride, or bisphosphonates during the previous 12 months
• Any condition predisposing to hypercalcaemia
• Nephrolithiasis or renal insufficiency
• Presence of primary hyperparathyroidism, hyperthyroidism, or hypothyroidism in the year before the study began; a history of nephrolithiasis during the previous five years.