ORIGINAL ARTICLE Association between prolonged breastfeeding and bone mineral density and osteoporosis in postmenopausal women: KNHANES 2010-2011 I. R. Hwang 1 & Y. K. Choi 1 & W. K. Lee 2 & J. G. Kim 1 & I. K. Lee 1 & S. W. Kim 1 & K. G. Park 1 Received: 15 March 2015 /Accepted: 12 August 2015 # International Osteoporosis Foundation and National Osteoporosis Foundation 2015 Abstract Summary This study showed that a negative correlation be- tween duration of breastfeeding and bone mineral density (BMD) in the lumbar spine and prolonged breastfeeding is an independent risk for osteoporosis in postmenopausal wom- en. The present study suggests that postmenopausal women with a history of prolonged breastfeeding require more careful screening for osteoporosis. Introduction Several studies suggest that breastfeeding and childbirth lead to maternal calcium loss and a decline in BMD. While the association between breastfeeding and BMD immediately after weaning is well-established, the ef- fects of breastfeeding on postmenopausal women have been controversial. The aim of this study was to examine the effects of breastfeeding on bone mineral density (BMD) and the prev- alence of osteoporosis in postmenopausal women. Methods The present study was a cross-sectional survey based on the Korea National Health and Nutrition Examination Survey (KNHANES) 2010 and 2011 data. The association between breastfeeding and BMD and osteoporosis was examined in 1222 postmenopausal women. Results The duration of breastfeeding and BMD in the lumbar spine showed a negative correlation. The association between duration of breastfeeding and BMD remained significant after adjustment for reproductive factors and other confounding factors (P =0.008). However, the number of deliveries and age at the time of delivery did not correlate with BMD at any site after adjustment. Moreover, the prevalence of osteoporosis in postmenopausal women with a history of prolonged breastfeeding was significantly higher than that in women with a short history of breastfeeding (≥37 months, OR=3.292; 95 % CI 1.485–7.299). The prevalence of lumbar spine fracture showed a significant increasing trend with the increase in the duration of breastfeeding. Conclusion Prolonged breastfeeding was significantly associ- ated with low BMD in the lumbar spine and higher prevalence of osteoporosis. However, the number of deliveries or age at the time of childbirth did not influence BMD. Keywords Bone mineral density . Breastfeeding . Osteoporosis . Postmenopausal women Introduction Osteoporosis is a metabolic bone disease associated with the micro-architectural deterioration of bone mass [1]. Bone min- eral density (BMD) is affected by various factors related to calcium homeostasis [2, 3]. A negative calcium balance caused by various conditions (e.g., high renal acid load, high salt diet, or vitamin D deficiency) results in bone mineral loss because calcium is removed from bones to maintain calcium concentration in serum [4, 5]. Pregnancy and breastfeeding are also associated with increase of maternal calcium loss and have a deleterious effect on osteoporosis [6, 7]. During I. R. Hwang and Y. K. Choi contributed equally to this work. * S. W. Kim sungwoocap@naver.com * K. G. Park kpark@knu.ac.kr 1 Division of Endocrinology and Metabolism, Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, South Korea 2 Department of Preventive Medicine, Kyungpook National University School of Medicine, Daegu, South Korea Osteoporos Int DOI 10.1007/s00198-015-3292-x