No independent association between dietary calcium/vitamin D and appendicular lean mass index in middle-aged women: NHANES cross-sectional analysis (2011-2018).

Skeletal muscle preservation during midlife is critical for preventing sarcopenia in aging populations. While calcium and vitamin D are recognized for their musculoskeletal benefits, their specific associations with muscle mass in middle-aged women remain unclear. This cross-sectional study analyzed data from 2,496 women aged 40-59 years in the NHANES (2011-2018). Multivariable linear regression models adjusted for demographics, lifestyle factors, and comorbidities evaluated associations between dietary calcium, vitamin D intakes and appendicular lean mass index (ALMI), with subgroup analyses by menopausal status and other covariates. After full adjustment, neither dietary calcium nor vitamin D intake showed significant associations with ALMI. Null findings persisted across all subgroups. Dietary calcium and vitamin D intake were not independently associated with ALMI in middle-aged women. These results highlight the need to investigate broader nutritional patterns or synergistic mechanisms influencing muscle health during midlife.