The concurrent presence of low bone density (osteopenia/osteoporosis) and low muscle mass (sarcopenia) in older adults has led to the recognition of “osteosarcopenia” (OS) as a singular entity. Vitamin D may play important role in the manifestation of OS, in terms of intake, absorption, and bioavailability. Evidence suggests that bioavailable 25(OH)D may be a better indicator of Vitamin D compared to total 25(OH)D due to its weak bind to albumin, increasing its ‘availability’. The aim of this study was to assess total and bioavailable 25(OH)D levels in postmenopausal women and to determine their associations to bone density and muscle mass. We assessed body composition, bone density, and 25(OH)D indices of multiethnic, postmenopausal Malaysian women. A significant and negative correlation was found between body fat % and each index of 25(OH)D. Both bioavailable and total 25(OH)D were positively correlated with serum calcium and negatively correlated with iPTH. VDBP level was significantly correlated with bioavailable 25(OH)D level, but not with the total 25(OH)D level. Stepwise regression analysis revealed that bioavailable, but not total, 25(OH)D was significantly correlated to bone density and muscle mass, (where stronger correlation was found with bone density), suggesting its superiority. Nevertheless, the low effect size warrants further studies.

中文翻译：

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总生物利用度与生物利用度：确定更好的25（OH）D指数与绝经后妇女的骨密度和肌肉质量相关

老年人同时存在低骨密度（骨质减少/骨质疏松症）和低肌肉量（肌肉减少症）已导致将“骨骨减少症”（OS）识别为单一实体。就摄入，吸收和生物利用度而言，维生素D可能在OS的表现中起重要作用。有证据表明，与总的25（OH）D相比，可生物利用的25（OH）D与总的25（OH）D相比可能是维生素D的更好指标，因为它与白蛋白的结合较弱，从而增加了其“利用率”。这项研究的目的是评估绝经后妇女的总和生物利用性25（OH）D水平，并确定她们与骨密度和肌肉质量的关系。我们评估了多种族，绝经后的马来西亚女性的身体成分，骨密度和25（OH）D指数。发现体内脂肪百分比与25（OH）D的各个指标之间存在显着负相关。生物利用度和总25（OH）D与血清钙呈正相关，与iPTH呈负相关。VDBP水平与生物可利用的25（OH）D水平显着相关，但与总25（OH）D水平无关。逐步回归分析显示，生物利用度（而非总生物利用度）25（OH）D与骨密度和肌肉质量显着相关（其中发现与骨密度的相关性更强），表明其优越性。然而，低效应值值得进一步研究。25（OH）D与骨密度和肌肉质量显着相关（其中与骨密度的相关性更强），表明其优越性。然而，低效应值值得进一步研究。25（OH）D与骨密度和肌肉质量显着相关（其中发现与骨密度的相关性更强），表明其优越性。然而，低效应值值得进一步研究。