Table 2.

Human studies showing the impact of metabolic acid load status on muscle mass.

Author	Subjects 1	Age (year)	Study Type	Variables Measured	Results	Duration/Design
Welch et al., 2013 [63]	2689 women	18–79	Cross-sectional	Fat mass Fat-free mass PRAL	Lower quartile of PRAL correlates with a less preserved fat-free mass	-
Chan, 2015 [64]	3122 men and women	>65	Cohort Prospective	Axial muscle mass Energy-adjusted NEAP	Participants in the highest quartile of energy-adjusted estimated NEAP lost significantly more muscle mass than those in the lowest	4 years
Frassetto et al., 1997 [65]	14 postmenopausal women	51–77	Intervention clinical trial	NAE Nitrogen excretion	Alkali supplementation reduced NAE and nitrogen excretion	18 days 60–120 mmol/day of KHCO3
Ceglia et al., 2009 [62]	19 men and women	54–82	Double-blind, randomized, placebo-controlled study	IGF-I Urinary nitrogen Urinary calcium	KHCO3 reduced the rise in urinary nitrogen excretion that accompanied an increase in protein intake	90 mmol/day of KHCO3 41 days 2
Dawson-Hughes, 2010 [66]	71 men 91 women	>50	Double-blind, placebo-controlled trial	NAE Nitrogen excretion Muscle power Training endurance	KHCO3 reduced NAE and nitrogen excretion. In women, bicarbonate increased double leg press power at 70% one repetition maximum by 13%	67.5 mmol/day of KHCO3 for 3 months

¹ All studies are performed on healthy subjects with no metabolic conditions. ² KHCO₃ or placebo with a 16-day phase-in and two successive 10-day diets at low (0.5 g/kg) or high (1.5 g/kg) protein in randomly assigned with a five-day washout period between diets.