Nonlinear dose-response relationship between dietary niacin intake and osteoporosis in U.S. adults over 50 years of age — A cross-sectional study of the 2007-2018 National Health and Nutrition Examination Survey (NHANES). - Bai, Jia; Gao, Botao; An, Jinyang; Li, Lingling; Zhang, Yangyang; Li, Xinsai; Li, Shuyun; Lv, Haihong (Nutrición Hospitalaria, 2025)