Dietary Inflammatory Index is intensity-dependently associated with the Bone Mineral Density at the Lumbar Spine: A Cross- Sectional NHANES Study from 2007 to 2020

Background Bone mineral density (BMD) is a tool to assess bone health. Dietary inflammation index (DII) is an index to reflect the inflammatory effect of a diet. Even though the association between DII and BMD have been extensively studied, the outcome remains controversial. This study aims to reveal the relationship between DII and lumbar spine BMD in both the whole population and in postmenopausal women. Methods We utilized data from the National Health and Nutrition Examination Survey (NHANES) 2007–2020 and included 27027 participants after exclusion procedure. Smooth curve fitting and multivariate regression analysis were used both in the entire population and later in the subgroup analysis. Results In the entire population, the smooth curve fitting revealed a non-linear association with both declining and increasing trends between DII and lumbar spine BMD. Multivariate regression analysis indicated that, after adjustment, the median DII and BMD was negatively associated and the high DII and BMD was positively associated. In postmenopausal women, smooth curve fitting suggested an inverted U-shaped relationship between DII and BMD. We also observed a positive correlation between low DII and lumbar spine BMD. Conclusions DII has both positive and negative relationship with lumbar spine BMD in both the entire population and menopausal women, depending on the intensity of DII. The different trends of the smooth curve fitting may be explained by the low-inflammation state in postmenopausal women mediated by estrogen but more evidence is needed to explain the reason.