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Am J Clin Nutr. 2017 Nov;106(5):1257-1266. doi: 10.3945/ajcn.117.158113. Epub 2017 Sep 13.

In the elderly, meat protein assimilation from rare meat is lower than that from meat that is well done.

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Unit of Human Nutrition, French National Institute for Agricultural Research, University of Clermont Auvergne, Clermont-Ferrand, France.
Unit of Physiology of Nutrition and Food Behavior, AgroParisTech, French National Institute for Agricultural Research, University of Paris-Saclay, Paris, France.
ADIV, Clermont-Ferrand, France; and.
Center for Research in Human Nutrition Auvergne, Clermont-Ferrand University Hospital, Clermont-Ferrand, France.
Clinical Nutrition Service and.
Quality of Animal Products, French National Institute for Agricultural Research, Saint Genès-Champanelle, France.
Unit of Human Nutrition, French National Institute for Agricultural Research, University of Clermont Auvergne, Clermont-Ferrand, France;


Background: Meat cooking conditions in in vitro and in vivo models have been shown to influence the rate of protein digestion, which is known to affect postprandial protein metabolism in the elderly.Objective: The present study was conducted to demonstrate the effect of cooking conditions on meat protein assimilation in the elderly. We used a single-meal protocol to assess the meat protein absorption rate and estimate postprandial meat protein utilization in elderly subjects.Design: The study recruited 10 elderly volunteers aged 70-82 y. Each received, on 2 separate occasions, a test meal exclusively composed of intrinsically 15N-labeled bovine meat (30 g protein), cooked at 55°C for 5 min [rare meat (RM)] or at 90°C for 30 min [fully cooked meat (FCM)], and minced. Whole-body fluxes of leucine, before and after the meal, were determined with the use of a [1-13C]leucine intravenous infusion. Meat protein absorption was recorded with the use of 15N enrichment of amino acids.Results: Postprandial time course observations showed a lower concentration in the plasma of indispensable amino acids (P < 0.01), a lower entry rate of meat leucine in the plasma (P < 0.01), and a lower contribution of meat nitrogen to plasma amino acid nitrogen (P < 0.001), evidencing lower peripheral bioavailability of meat amino acids with RM than with FCM. This was associated with decreased postprandial whole-body protein synthesis with RM than with FCM (40% compared with 56% of leucine intake, respectively; P < 0.01).Conclusions: Whereas meat cooking conditions have little effect on postprandial protein utilization in young adults, the present work showed that the bioavailability and assimilation of meat amino acids in the elderly is lower when meat is poorly cooked. In view to preventing sarcopenia, elderly subjects should be advised to favor the consumption of well-cooked meat. This trial was registered at as NCT02157805.


amino acid bioavailability; cooking; elderly; meat; protein metabolism

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