Fluid balance and acid load (see a great article by JB on this can make a difference. The box in the text below is a +/- symbol that did not transfer.
In the meantime, here is a synopsis of a study we published a few years back:
Abstract #631.14- Experimental Biology(FASEB) March 31-April 4, 2001. Orlando, FL.
The Effects of a High Protein Intake on Markers of Health in Weight Trained Athletes.
D. Kalman1, J. Antonio2. 1Miami Research Associates, Miami, FL 2University of Delaware, Newark, DE.
The purpose of this study was to evaluate the effects of a high protein intake on markers of safety (leukocytes, liver and renal function, urinary ketones and protein) in 20 healthy resistance-trained males. At baseline, subjects? average macronutrient intake consisted of 27% protein (1.5 g/kg), 47% carbohydrate and 26% fat. Protein intake was increased to 40% (2.88 g/kg) of total calories, which resulted in CHO intake decreasing to 37% and fat intake to 23% for 28 days. Each subject was allowed to follow their normal exercise routines (weight-training, 4-days per week, split body workouts). At baseline, day 14, and day 28, each subject underwent anthropometric testing, urinalysis, and full blood chemistry analysis. Baseline characteristics: age 32.32 11.1 yr, height 180.55.1 cm, weight 87.4912.4 kg. Data was analyzed via the Signed Rank Test for significant changes over time (p<0.05). Pre weight 87.49-Post 88.05 kg:NS; Pre urinary ketones 3.95-Post 1.58:NS; Pre urinary protein 11.58-post 11.68:NS; Pre WBC 7.78-post 7.83x10x9/L:NS; Pre BUN 18.21-post 21.05 mg/dl:p=0.02; Pre creatinine 1.12-post 1.21mg/dl:p=0.006; Pre AST 27.21-post 29 U/L:NS; Pre ALT 28-post 29.89 U/L:NS; Pre GGT 27.21-post 25.37U/L:NS and dietary protein intake 27 to 40%:p=0.0001. Although still remaining within normal limits, the significant changes observed in the BUN and creatinine over the 28 days were due to normal healthy renal adaptation to a higher protein load. In conclusion, the daily high protein intake (3.6x RDI) had no untoward or negative effects on the immune system, renal and hepatic function nor did it induce ketosis or dehydration, thus it appears safe for short-term daily intake.