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Percentage lean body mass is lower with a higher dietary acid–base load in women aged 18–79 years

Published online by Cambridge University Press:  17 March 2010

A. A. Welch ,
A. Cassidy ,
S. Fairweather-Tait ,
T. Spector  and
A. MacGregor
A. A. Welch
Affiliation:
Medical School, University of East Anglia, Norwich NR4 7TJ, UK
A. Cassidy
Affiliation:
Medical School, University of East Anglia, Norwich NR4 7TJ, UK
S. Fairweather-Tait
Affiliation:
Medical School, University of East Anglia, Norwich NR4 7TJ, UK
T. Spector
Affiliation:
King's College London, London SE1 7EH, UK
A. MacGregor
Affiliation:
Medical School, University of East Anglia, Norwich NR4 7TJ, UK
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Abstract

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Information
Proceedings of the Nutrition Society , Volume 69 , Issue OCE1: Over- and undernutrition: challenges and approaches. 29 June–2 July 2009 , 2010 , E80
Copyright
Copyright © The Authors 2009

Falls are a major risk for fracture and the age-related decline in muscle mass and strength is a key contributor to falls(Reference Dawson-Hughes1). Bone density is also a predictor of fracture risk, and muscle mass is related to bone density. Thus, it is important to identify factors that affect muscle mass.

Besides the known effects of age and physical activity, nutrition has the potential to influence maintenance of muscle mass. Metabolic acidosis is related to a decline in muscle mass in renal failure, and metabolic acidosis affects protein metabolism by decreasing protein synthesis and increasing N excretion even in healthy individuals(Reference Wiederkehr and Krapf2). Thus, it is possible that mild metabolic acidosis could influence muscle mass in healthy individuals. The acid–base load of diet is known to influence acid-base status and so the association between dietary acid–base load (estimated as potential renal acid load (PRAL)) and percentage lean body mass (LBM) was investigated in a study of female twins aged 18–79 years.

LBM was measured using dual-energy X-ray absorptiometry (Hologic (UK) Ltd, Crawley, West Sussex, UK) in 2720 female twins and converted to percentage LBM by dividing by body weight(Reference Cassidy, Skidmore and Rimm3). PRAL was measured using an FFQ and divided into quartiles, and calculated using the formula: PRAL=(P*0.0366+protein*0.4888)−(K*0.0205+Ca*0.0125+mg*0.0263)(Reference Remer, Dimitriou and Manz4). LBM values were calculated according to quartile of PRAL and are presented unadjusted and adjusted for covariates using robust regression with the cluster option in STATA version 9.1 (StataCorp, College Station, TX, USA) in the Table.

There was a significant difference in LBM of 1.1% between quartile 1 of PRAL and quartile 4 of PRAL (most acidic) after adjustment for covariates (see Table).

*Adjusted for age, physical activity and smoking habit.

There was a cross-sectional decrease in LBM with a higher (more acidic) PRAL intake and although this difference was relatively small, it was significant and independent of the effects of age and physical activity. Further analyses are ongoing in this twin study to determine the heritable and familial determinants of LBM.

References

1. Dawson-Hughes, B (2008) Am J Clin Nutr 87, 662–665.CrossRefGoogle Scholar
2. Wiederkehr, M & Krapf, R (2001) Swiss Med Wkly 131(9–10), 127–132.Google Scholar
3. Cassidy, A, Skidmore, P, Rimm, EB et al. (2009) J Nutr 139, 353–358; Epublication 23 Dec 2008.CrossRefGoogle Scholar
4. Remer, T, Dimitriou, T & Manz, F (2003) Am J Clin Nutr 77, 1255–1260.CrossRefGoogle Scholar