Effects of vitamin D deficiency and daily calcium intake on bone mineral density and osteoporosis in Korean postmenopausal woman

OBJECTIVE We evaluated the combined effects of vitamin D and daily calcium intake on bone mineral density (BMD) and osteoporosis in Korean postmenopausal women. METHODS This study is a cross-sectional study consisting of 1,921 Korean postmenopausal women aged 45 to 70 years without thyroid dysfunction, from the 2008-2011 Korean National Health and Nutrition Examination Survey. Participants were classified into six groups according to serum 25-hydroxyvitamin D (25(OH)D) levels and daily calcium intake. BMD was measured using dual-energy X-ray absorptiometry at femur and at lumbar spine, and the serum vitamin D levels were measured by radioimmunoassay. RESULTS The BMD divided according to serum 25(OH)D and daily calcium intakes were not statistically different among the groups. However, when both daily calcium intake and serum 25(OH)D were not sufficient, risk of osteopenia and osteoporosis showed significant increase in both femur neck and lumbar spine (odds ratio [OR] 2.242, P=0.006; OR 3.044, P=0.001; respectively). Although daily calcium intake was sufficient, risks of osteopenia and osteoporosis significantly increased in lumbar spine group if serum 25(OH)D is <20 ng/mL (OR 2.993, P=0.006). CONCLUSION The combined effects of insufficient daily calcium intake and vitamin D deficiency may cause low BMD and increase in prevalence of osteopenia and osteoporosis in Korean postmenopausal women aged 45 to 70 years.