Effect of a gum arabic supplement on the nitrogen excretion and serum urea nitrogen concentration of chronic renal failure patients on a low-protein diet
In chronic renal failure (CRF), urinary excretion of the products of protein metabolism, mainly urea, is markedly reduced due to a decrease in the glomerular filtration rate. Retention of these nitrogen metabolites has been associated with adverse clinical symptoms and may hasten the progression of CRF. Consequently, CRF patients are treated with a low protein diet (LPD). An alternate route of urea nitrogen excretion is via fecal bacteria which utilize nitrogen for growth. Fermentation of dietary fiber by colonic bacteria promotes their growth and nitrogen incorporation. The purpose of this study was to determine whether supplementing a LPD with a highly fermentable fiber, gum arabic, would increase fecal bacterial mass and fecal nitrogen excretion and thus lower serum urea nitrogen (BUN) levels in CRF patients. Sixteen CRF patients supplemented their LPD with 50g of gum arabic/day and 1g of pectin/day, used as a placebo fiber, for 28 days each in a randomized, single-blind, cross-over design. Fecal bacterial mass, fecal and urinary nitrogen content, BUN and dietary protein intake (for nitrogen balance) were measured using methods of stool fractionation, Kjeldahl analysis, colorimetric spectrophotometry, and computerized dietary record analysis, respectively. Results showed that, during the gum arabic supplement, fecal bacterial mass and the nitrogen content of the stool bacterial fraction were significantly greater than during the baseline LPD or pectin supplement. BUN levels were significantly lower during the gum arabic supplement than during the baseline LPD or pectin supplement. The weights of wet stool, total dry stool solids and the stool fractions containing water-soluble substances and undigested dietary fiber were significantly greater during the gum arabic supplement than during the baseline LPD or pectin supplement. The nitrogen contents of total dry stool solids and the water-soluble fraction were significantly greater during the gum arabic supplement than during the baseline LPD or pectin supplement. There was no significant difference in urinary nitrogen or nitrogen balance among the study periods. The results suggest that supplementing a LPD with gum arabic may benefit CRF patients by increasing fecal nitrogen excretion and lowering BUN levels
