Interaction of dietary acid load and general and central obesity with muscle strength and skeletal muscle mass.

ABSTRACT

BACKGROUND: We aimed to examine the combined association of dietary acid load and obesity with muscle strength. METHODS: This cross-sectional study was conducted on 270 adults (118 men and 152 women), aged 18-70 y. Dietary data were collected using a validated 168-item semi-quantitative food frequency questionnaire. Potential renal acid load (PRAL), net endogenous acid production (NEAP), and dietary acid load (DAL) were calculated. General obesity was defined as a body mass index (BMI) ≥30 kg/m2 and abdominal obesity was defined as a waist circumference (WC) ≥102 cm for men and ≥88 cm for women. Muscle strength was measured by a digital handgrip dynamometer. RESULTS: The mean of muscle strength was higher in participants classified as high-PRAL/BMI≥30 (P = 0.01), high-PRAL/WC < 102 (men) or 88 (women) (P = 0.002), high-NEAP/BMI≥30 (P = 0.002), high-NEAP/WC < 102 (men) or 88 (women) (P < 0.001) and also high-DAL/BMI≥30 (P = 0.01) and high-DAL/WC < 102 (men) or 88 (women) (P = 0.001) compare to other classifications in the crude model. Both for obese and non-obese people PRAL, NEAP, and DAL were associated with higher muscle strength, which is opposite to the acid hypothesis. These associations were not significant after adjustment for confounders. Also, the mean of skeletal muscle mass was higher in participants that were classified as high-PRAL/BMI≥30 and high-PRAL/WC < 102 (men)-or-88 (women), high-NEAP/BMI≥30, and high-NEAP/WC < 102 (men)-or-88 (women), high-DAL/BMI≥30 and high-DAL/WC < 102 (men)-or-88 (women) (Ptrend<0.001 for all). These significant associations remained significant after controlling for confounders. CONCLUSIONS: We found that the interaction of dietary acid load and general and central obesity could be associated with skeletal muscle mass but not muscle strength. All findings of association indicated higher muscle strength and skeletal muscle mass with higher acid diet measures, contrary to the acid hypothesis.