INTRODUCTION: This study aimed to investigate the effects of quercetin (a plant-based flavonoid) supplementation over 90 days on prominent bone turnover markers (BTMs), inflammatory markers, bone mineral density (BMD), body composition, and physical function in postmenopausal women. MATERIALS AND METHODS: Thirty-three healthy postmenopausal women were recruited to participate in a double-blind, placebo-controlled investigation. Participants were randomized into one of two supplement groups: (1) 500 mg of quercetin (QUE) once daily or (2) 500 mg of methylcellulose (placebo
PLB) once daily. Pre- and post-testing visits included assessments of BTMs (i.e., osteocalcin [OC], procollagen type I N-terminal propeptide [PINP], and type I collagen cross-linked C-terminal telopeptide [CTX]), inflammatory markers (i.e., interleukin [IL]-6, tumor necrosis factor-alpha [TNF-α], and C-reactive protein [CRP]), BMD measurements, body composition measurements, and physical function including timed up and go and handgrip strength. RESULTS: The QUE group increased OC (p = 0.016
d = 0.89), PINP (p = 0.030
d = 0.64), and CTX (p = 0.023
d = 0.91) levels and decreased IL-6 (p = 0.045
d = 0.73) and TNF-α (p = 0.021
d = 0.90) levels compared to PLB. CRP (p = 0.448
d = 0.34), body composition (p >
0.05), and physical function (p >
0.05) remained unchanged. CONCLUSION: The results suggest that QUE may better assist in controlling a normal bone turnover cycle by mediating bone formation and decreasing pro-inflammatory cytokines. However, although within the accepted range, there was an increase in the bone resorption marker and therefore, it is unclear if QUE will protect against future bone loss. Nonetheless, additional research is necessary to evaluate the bone-conserving properties of QUE among postmenopausal women. CLINICAL TRAIL REGISTRATION: The ClinicalTrials.gov ID number: NCT05371340.