Dietary acid-base load and its association with risk of osteoporotic fractures and low estimated skeletal muscle mass

Background/objectives: Age-related decline in skeletal muscle mass and strength, loss of bone density, and increased risk of osteoporotic fractures are important public health issues. Systemic acid–base balance is affected by dietary intake and may be relevant to these conditions. We therefore investigated associations of dietary acid–base load with skeletal muscle mass, bone density status, and fracture risk. Subjects/methods: We analysed the European Prospective Investigation into Cancer and Nutrition-Norfolk cohort of >25,000 individuals, 39–79 years at baseline. Potential renal acid load (PRAL) was calculated from 7-day food diary data. As a proxy for skeletal muscle mass, we estimated fat-free mass from bioelectrical impedance analysis and scaled this for BMI (FFM _BMI). Bone density status was assessed by heel-bone broadband ultrasound attenuation (BUA), and fracture rates were obtained from health-care records. Multivariable regression was used to test musculoskeletal outcomes across sex-specific quintiles of PRAL. Results: PRAL in quintiles was negatively associated with FFM _BMI in men (n = 6350, p < 0.001) and women (n = 7989, p < 0.001), with quintile 5 vs 1 differences of −1.5% and −3.2% (both p < 0.001). PRAL was also negatively associated with BUA in women (n = 8312, p = 0.016; quintile 5 vs 1 difference −1.5%, p = 0.024). The combined hazard of hip, wrist and spine fractures (mean ± SD follow-up 17.9 ± 4.9 years) was higher with increasing quintiles of PRAL in men (610 fractures; n = 11,511; p = 0.013) and women (1583 fractures; n = 13,927; p = 0.009), with quintile 5 vs 1 hazard ratios of 1.33 (95% CI: 1.03–1.72, p = 0.029) and 1.21 (95% CI: 1.03–1.42, p = 0.022), but associations were not consistent for all fractures sites and age groups tested. Conclusions: This study provides strong evidence, albeit observational, for a negative association between PRAL and musculoskeletal health in middle to older age men and women, and thus supports the rationale for a less acidic dietary load.