Daily Vitamin D Supplementation Compared to a Loading Dose and Monthly Supplementation in Elderly Nursing Home Residents

Vitamin D deficiency is common in older persons, in particular in residents of nursing homes. This is mainly explained by the fact that older persons do not often go outside in the sunshine. On top of that the capacity of the skin to synthesize provitamin D is decreased and dietary vitamin D intake is low. Vitamin D deficiency leads to osteoporosis, falls and fractures. To prevent morbidity and mortality due to falls and fractures it seems logical to supplement vit D in order to correct the deficiency. The advised daily dose of vit D supplementation is 800 IU. Several studies showed that with this dose the required serum 25(OH)D levels will not be reached. primary objective of this study is: * to investigate whether with a loading dose based on body weight and baseline serum 25(OH)D level more patients reach adequate serum 25(OH)D levels compared to 800 IU a day. * to determine the best consolidation treatment. Secondary objective * is a loading dose based on body weight and baseline serum 25(OH)D level safe to use in residents of nursing homes. * is there a relation between the increase in serum 25(OH)D level and muscle strength (handgrip strength). * is there a relation between the increase in serum 25(OH)D level and mobility (2 minute walk test). Study design: Randomised trial with 3 study groups: * Group 1a. loading dose based on body weight and baseline serum 25(OH)D level + 50.000 IU vit D3/month consolidation therapy. * Group 1b. loading dose based on body weight and baseline serum 25(OH)D level + 25.000 IU vit D3/month consolidation therapy. * Group 2. 800 IU vit D3/ dag. Study population: Vitamine D deficient residents of nursing homes, 65 years or older.