The aim of this study is to compare oral vitamin D supplementation administered in two different ways, namely either twice a day (800IU/d, 292000IU/y) or three times a year (97333IU every 4 months, 292000IU/y) in elderly women in combination with daily supplementation of calcium 1 gram. We will 1)compare the blood concentrations of 25 OH vitamin D in the two treatment groups amd monitor if a sufficient and safe concentration of 25OH D in blood can be maintained with these two treatments.2) Find out seasonal variation in vitamin D concentrations in these treatments. 3) Find out safety of these treatments