The rate of protein digestion affects protein gain differently during aging in XXXX .

@entity1 @entity1741 @entity368
In young @entity1 ingesting protein meals, slowly digested proteins (caseins: @entity1741 ) induce a higher protein gain than those that are rapidly digested (whey proteins: WP). Our aim was to assess whether or not this is true in elderly @entity1 receiving mixed meals. The effects of meals containing either @entity1741 or two different amounts of WP (WP-iN: isonitrogenous with @entity1741 , or WP-iL: providing the same amount of @entity368 as @entity1741 ) on protein metabolism (assessed by combining oral and intravenous @entity368 tracers) were compared in nine healthy, elderly (mean +/- S.E.M. age 72 +/- 1 years) and six young @entity1 (24 +/- 1 years). In both age groups, WP-iL and WP-iN were digested faster than @entity1741 (P < 0.001, ANOVA). Proteolysis was inhibited similarly whatever the meal and age groups (P = NS). Protein synthesis was higher with WP-iN than with @entity1741 or WP-iL (P < 0.01), irrespective of age (P = NS). An age-related effect (P < 0.05) was found with postprandial @entity368 balance. @entity368 balance was higher with @entity1741 than with WP-iL (P < 0.01) in young @entity1 , but not in elderly subjects (P = NS). In isonitrogenous conditions, @entity368 balance was higher with WP-iN than with @entity1741 (P < 0.001) in both age groups, but the magnitude of the differences was higher in the elderly @entity1 (P = 0.05). In conclusion, during aging, protein gain was greater with WP (rapidly digested protein), and lower with @entity1741 (slowly digested protein). This suggests that a 'fast' protein might be more beneficial than a 'slow' one to limit protein losses during aging.
