Using Ca-41 Methodology to Assess the Impact of Different Vitamin D Supplementation Levels on Postmenopausal Bone Health

Inclusion Criteria: * apparently healthy women, at least 5 years post-menopausal * BMI 18-30 * no HRT * no regular intake of Ca or vit D supplements * wiling and able to give written informed consent and to understand, participate and comply with study requirements * non-smokers * no long travels (\>3 wk) planned within study period Exclusion Criteria: * diseases that predispose to osteoporosis * history of fragility fractures * currently on a weight reduction program * excessive physical activity * diseases influencing calcium metabolism (thyroid, parathyroid, adrenal disorders etc.) * regular intake of medication affecting calcium metabolism * osteoporosis (T-score below -2.5) * history of psychological illness likely to interfere with the subject's ability to understand the requirements of the study * participation in concurrent studies