Effects of the type and level of dietary fibre supplements on nitrogen retention and excretion patterns

• Published in: British journal of nutrition Vol. 75; no. 3; pp. 461 - 469
• Main Authors: Tetens, Inge, Livesey, G., Eggum, B. O.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.03.1996
• Subjects: Animals; Biological and medical sciences; Cellulose - administration & dosage; Dietary Fiber - administration & dosage; Dietary Fiber - pharmacology; Dietary fibre; dietary fibre supplements and nitrogen metabolism; Feces - chemistry; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; Glycine max; Male; Nitrogen - analysis; Nitrogen - metabolism; Nitrogen - urine; Nitrogen excretion; Nitrogen retention; Pectins - administration & dosage; Rats; Rats, Wistar; Regression Analysis; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Zea mays; Nitrogen retention; Nitrogen excretion; Dietary fibre; Vertebrata; Excretion; Mammalia; Rat; Diet; Rodentia; Metabolism; Nitrogen; Dietary fiber; Retention; Source; Feeding
• ISSN: 0007-1145; 1475-2662
• DOI: 10.1079/BJN19960147

The hypothesls was tested that fermentable dietary fibre (DF) sources elevate faecal N excretion at the expense of urinary N without affecting N retention. DF that substantially increase fermentation (pectin, Sugarbeet and soya bran) or are poorly fermented (crystalline cellulose and maize bran) were fed as supplements to a basal DF-free diet a t three dose levels: 0,50 and 100 g supplement/kg basal diet. The diets were fed to juvenile male Wistar rats for 2 weeks before a 7 d period when faeces and urine were collected. Faecal excretion of N was significantly increased, dose-dependently, by all DF supplements and was positively correlated to faecal bulking. Urinary excretion of N was lower at the high doses of the DF supplements but reached significance only with the highly fermentable (0·68) sugarbeet- supplementeddiets. Regression analysis showed that the major part (0·75) of the increase in faecal N excretion due to DF supplementation was balanced by a reduction in urinary excretion; N retention was therefore, at the dose levels used, only affected to a small extent. Only in the maize-bran-supplemented diets were the reductions in N retention significant. The shift in N excretion from urine to faeces can be explained largely by the degree of microbial fermentation in the large intestine caused by the addition of DF supplements and emphasizes the modifying role that certain DF supplements may have on the enterohepatic cycle of N. Possible implications of these findings for patients with liver or renal failure or for conditions when the intake of dietary protein is marginal are discussed.