Long-term high intake of whole proteins results in renal damage in pigs

Despite evidence of potential antiobesity effects of high-protein (HP) diets, the impact of consuming diets with protein levels at the upper limit of the acceptable macronutrient distribution range (AMDR) on kidney health is unknown. To test whether HP diets affect renal health, whole plant and animal proteins in proportions that mimicked human diets were given to pigs, because their kidneys have a similar anatomy and function to those of humans. Adult female pigs received either normal-protein (NP) or HP (15 or 35% of energy from protein, respectively) isocaloric diets for either 4 or 8 mo. The higher protein in the HP diet was achieved by increasing egg and dairy proteins. Although there were initial differences in body weight and composition, after 8 mo these were similar in pigs consuming the NP and HP diets. The HP compared with NP diet, however, resulted in enlarged kidneys at both 4 and 8 mo. Renal and glomerular volumes were 60-70% higher by the end of the study. These enlarged kidneys had greater evidence of histological damage, with 55% more fibrosis and 30% more glomerulosclerosis. Renal monocyte chemoattractant protein-1 levels also were 22% higher in pigs given the HP diet. Plasma homocysteine levels were higher in the HP pigs at 4 mo and continued to be elevated by 35% at 8 mo of feeding. These findings suggest that long-term intakes of protein at the upper limit of the AMDR from whole protein sources may compromise renal health.