Determination of Vitamin D Dose to Maintain Sufficiency Amongst Indian and Malay Women in the Tropics

Much research on vitamin D status has focused on seasonal variations in serum 25(OH)D levels in populations living at high altitudes and those of light-skinned Caucasian extraction, with little work done in multi ethnic populations living closer to the equator with regards to Vitamin d supplementation, prevalence, predictors and associations of hypovitaminosis D - the assumption, perhaps being vitamin D deficiency is unlikely in locations of plentiful sunshine. There is a dearth of studies on Vitamin D status in a group of subjects at especially high risk of falls/fractures i.e. post-menopausal women with osteoporosis living in South-East Asia. It is possible that differences in geography and ethnicity/culture amongst women with post menopausal osteoporosis (PMO) in Malaysia may necessitate supplemental Vitamin D doses that differ from those prescribed to North American Caucasians. There is no unified consensus on the dose of Vitamin D supplementation. Neither is there agreement on definitions of sufficiency with some researchers targeting levels of serum 25(OH)D of \>20ng/ml and others aiming for levels above 30ng/ml. The Institute of Medicine (IOM) 2010 guidelines, aiming for a lower serum 25(OH)D target of 20ng/ml, advocates maintenance doses of 600 IU/day in Postmenopausal women aged 51-70 and 800 IU/day for those aged \>70 years. On contrary, the Endocrine Society 2011 guidelines state that maintenance doses up to 1500-2000 IU/day may be required to attain a higher optimal target of \>30ng/ml. On addition, the 2014 National Osteoporosis Foundation Guidelines recommended that the Vitamin D level should be brought up to approximately 30ng/ml, and to maintain at this level taking into account those with limited sun exposure, obese and dark skin individuals, the daily requirement ranges from 800-2000 IU/day. The investigators therefore designed a prospective randomized controlled trial comparing efficacy and safety of a low (900 IU/day) and high (1800IU/day and 3