Short-term protein and energy supplementation activates nitrogen kinetics and accretion in poorly nourished elderly subjects

Background: An increase in protein intake exerts a stimulating effect on pr otein kinetics in children, young adults, and healthy elderly persons. Howe ver, there are few data on the response to such dietary changes in malnouri shed elderly subjects, despite important medical implications in this popul ation. Objective: The objective of this study was to determine the metabolic respo nse to short-term nutritional supplementation in moderately malnourished el derly subjects. Design: The influence of 10 d of supplementation (1.67 MJ/d and 30 g protei n/d) on body composition, resting energy expenditure, and whole-body protei n kinetics was studied in 17 malnourished elderly patients and 12 healthy y oung adults. A control group of 6 malnourished elderly patients received no supplementation. Results: Supplemented elderly subjects had a significantly greater fat-free mass gain than did unsupplemented elderly subjects (1.3 and 0.1 kg, respec tively; age effect, P < 0.05; diet effect, P < 0.02) and a significantly gr eater increase in fasting rate of protein synthesis than did young suppleme nted subjects (0.6 and 0.2 g.kg FFM-1.11 h(-1); age effect, P < 0.05). The net protein balance in the supplemented elderly subjects in the fed state w as positively correlated with protein intake (r(2) = 0.46) and in the faste d state was negatively correlated with protein intake (P = 0.27). The sum o f these regressions is a line with increasingly positive net diurnal protei n balance produced by increasing protein intake. Conclusion: These data provide evidence of a short-term anabolic response o f protein metabolism to dietary supplementation in malnourished elderly pat ients that is likely to improve muscle strength and functional status.