Level of dietary protein impacts whole body protein turnover in trained males at rest

Department of Nutritional Sciences, University of Connecticut, Storrs, CT 06269, USA.

"The current investigation examined the effect of variations in protein intake on Whole body protein turnover (WBPTO) at rest in endurance-trained males. Whole body protein turnover is influenced by both diet and exercise. Whether endurance athletes require more protein than the non-exerciser remains equivocal. Five male runners (21.3 +/- 0.3 years, 179 +/- 2 cm, 70.6 +/- 0.1 kg, 8.7% +/- 0.4% body fat, 70.6 +/- 0.1 VO(2)max) participated in a randomized, crossover design diet intervention where they consumed either a low-protein (LP; 0.8 g/kg), moderate-protein (MP; 1.8 g/kg), or high-protein (HP; 3.6 g/kg) diet for 3 weeks. Whole body protein turnover (Ra, leucine rate of appearance; NOLD, nonoxidative leucine disposal; and Ox, leucine oxidation), nitrogen balance, and substrate oxidation were assessed at rest following each dietary intervention period. The HP diet increased leucine Ra (indicator of protein breakdown; 136.7 +/- 9.3, 129.1 +/- 7.4, and 107.8 +/- 3.1 micromol/[kg . h] for HP, MP, and LP diets, respectively) and leucine Ox (31.0 +/- 3.6, 26.2 +/- 4.3, and 18.3 +/- 0.6 micromol/[kg . h] for HP, MP, and LP diets, respectively) compared with LP diet (P < .05). No differences were noted in nonoxidative leucine disposal (an indicator of protein synthesis) across diets. Nitrogen balance was greater for HP diet than for MP and LP diets (10.2 +/- 0.7, 1.8 +/- 0.6, and -0.3 +/- 0.5 for HP, MP, and LP diets, respectively). Protein oxidation increased with increasing protein intake (54% +/- 6%, 25% +/- 1%, and 14% +/- 2% for HP, MP, and LP diets, respectively). Findings from this study show that variations in protein intake can modulate WBPTO and that protein intake approximating the current recommended dietary allowance was not sufficient to achieve nitrogen balance in the endurance-trained males in this investigation. Our results suggest that a protein intake of 1.2 g/kg or 10% of total energy intake is needed to achieve a positive nitrogen balance. This is not a concern for most endurance athletes who routinely consume protein at or above this level."

For your information only 1.2 g/kg equals to o.55 g/LB. As the study suggests you will need more than that to achieve a positive nitrogen balance (one of the most important factors for muscle anabolism to occur). I mentioned several times what my recommendations are - 1 g/LB, which will surely put you in the "zone" (understand positive nitrogen balance and not the Barry Sears's zone:). More than that might place unnecessary stress on your system. The long effects of very high protein intake are still not well studied and documented. So, be on the safe side.