, aimed to balance energy needs. Before treatment and after 10 wk of intervention, whole-body and appendicular lean mass were measured by using dual-energy X-ray absorptiometry. Knee-extension peak power was measured with dynamometry. Results: Both groups were found to have been in a moderate negative energy balance (mean 6 SD RDA: 209 6 213 kcal/d; 2RDA 145 6 214 kcal/d; P = 0.427 for difference between the groups). In comparison with RDA, whole-body lean mass increased in 2RDA (P = 0.001; 1.49 6 1.30 kg, P , 0.001 compared with 20.55 6 1.49 kg, P = 0.149). This difference was mostly accounted for by an increase in trunk lean mass found in 2RDA (+1.39 6 1.09 kg, P , 0.001). Appendicular lean mass also decreased in RDA compared with 2RDA (P = 0.022), driven by a reduction in RDA (20.64 6 0.91 kg, P = 0.005 compared with 0.11 6 0.57 kg, P = 0.592). Adjusting for energy imbalances did not alter these findings. Knee-extension peak power was also differently affected (P = 0.012; 26.6 6 47.7 W, P = 0.015 in 2RDA compared with 211.7 6 31.0 W, P = 0.180 in RDA). Conclusions: Consumption of a diet providing 2RDA for protein compared with the current guidelines was found to have beneficial effects on lean body mass and leg power in elderly men. These effects were not explained by differences in energy balance. This trial was registered at the Australia New Zealand Clinical Trial Registry (www.anzctr.org.au) as ACTRN12616000310460.Am J Clin Nutr 2017;106:1375-83.

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Higher dietary protein intake is increasingly recommended for the elderly; however, high protein diets have also been linked to increased cardiovascular disease (CVD) risk. Trimethylamine-N-oxide (TMAO) is a bacterial metabolite derived from choline and carnitine abundant from animal protein-rich foods. TMAO may be a novel biomarker for heightened CVD risk. The purpose of this study was to assess the impact of a high protein diet on TMAO. Healthy men (74.2 ± 3.6 years, n = 29) were randomised to consume the recommended dietary allowance of protein (RDA: 0.8 g protein/kg bodyweight/day) or twice the RDA (2RDA) as part of a supplied diet for 10 weeks. Fasting blood samples were collected pre- and post-intervention for measurement of TMAO, blood lipids, glucose tolerance, insulin sensitivity, and inflammatory biomarkers. An oral glucose tolerance test was also performed. In comparison with RDA, the 2RDA diet increased circulatory TMAO (p = 0.002) but unexpectedly decreased renal excretion of TMAO (p = 0.003). LDL cholesterol was increased in 2RDA compared to RDA (p = 0.049), but no differences in other biomarkers of CVD risk and insulin sensitivity were evident between groups. In conclusion, circulatory TMAO is responsive to changes in dietary protein intake in older healthy males.