Protein requirements and ageing: metabolic demand and efficiency of utilization

The British Journal of Nutrition
A FeredayD J Millward

Abstract

The protein requirements of the elderly were investigated with [13C]leucine balance studies of metabolic demand, the efficiency of postprandial protein utilization (PPU) and the consequent apparent protein requirement. Ten elderly subjects aged 68-91 years (five men and five women) and ten young adult subjects aged 21-31 years (five men and five women) were infused with L-[1-13C]leucine for 9 h commencing in the postabsorptive state (0-3 h), continuing during the half-hourly feeding of low-protein meals (LP; protein 3% energy, 3-6 h), and during similar feeding of isoenergetic higher protein meals (HP; protein 15% energy, 6-9 h). Leucine oxidation and balance were determined from plasma [1-13C]-alpha-ketoisocaproate enrichment and expired 13CO2 excretion measured during the 3rd hour of each 3 h period. The protein intake during the HP phase was similar to the habitual intake estimated in the subjects from 24 h urinary N excretion. Metabolic demand was defined as equal to twice the body-protein equivalent of measured postabsorptive leucine oxidation. The efficiency of PPU was calculated from the increased leucine oxidation observed during feeding, and the apparent protein requirement was defined as metabolic demand/PPU and calcu...Continue Reading

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Citations

Oct 1, 1996·Baillière's Clinical Endocrinology and Metabolism·D J MillwardP J Pacy
Mar 21, 2012·The Proceedings of the Nutrition Society·D Joe Millward
Aug 31, 1999·The Proceedings of the Nutrition Society·D J Millward
Dec 22, 1999·The Proceedings of the Nutrition Society·B Lesourd, L Mazari
Aug 12, 2003·The British Journal of Nutrition·D J Millward
May 27, 1999·The Proceedings of the Nutrition Society·B Lesourd
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Aug 12, 2008·The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences·Agathe Raynaud-SimonCécile Loï
Mar 26, 2011·The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences·Stéphanie ChevalierJosé A Morais
Mar 19, 2002·Canadian Journal of Applied Physiology = Revue Canadienne De Physiologie Appliquée·D J Millward
Nov 8, 2012·The Journal of Nutrition, Health & Aging·M L AspM A Belury
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