Effect of dietary fiber components on fecal nitrogen excretion and protein utilization in growing rats

Determinants and consequences of colonic luminal pH: implications for colon cancer

Epidemiological data suggest that increased risk of colon cancer is correlated with a higher fecal pH. Although some experimental studies have shown a protective effect against experimentally induced colon cancer by acidifying colonic contents, others have shown that a more acidified colonic content is associated with increased cell proliferation and enhanced tumorigenesis. It is now clear that simply acidifying colonic contents will not consistently result in decreased tumorigenesis. Perhaps the key is how colonic contents are acidified--a decrease in base production or an increase in acid production. Or, more important than luminal pH itself, may be a factor affected by changes in hydrogen ion concentration. This paper reviews the determinants of colonic luminal pH and their dietary sources and discusses important physiological consequences of modifying the pH of colonic contents.

Effect of dietary fiber on proteolytic pancreatic enzymes in vitro

Chymotrypsin, trypsin, carboxypeptidase A and B, elastase and enterokinase activities were measured in buffer solutions and in human duodenal juice after incubation with wheat bran, cellulose, guar gum, pectin, psyllium and lignin. The different types of dietary fiber led to inhibition of enzymatic activity in most experiments, e.g., lignin could totally ablish the activity of isolated trypsin and chymotrypsin. Only in enterokinase was there no influence. Inhibition depended on incubation time; the effect was proportional to fiber concentration and inversely related to enzyme level. Treatment of fiber with hydrochloric acid (pH 1.5) and heat (95 degrees C) destroyed inhibitory activity in some experiments. The effect of lignin on one enzyme (trypsin) was reduced by the addition of another enzyme (chymotrypsin). It is concluded that dietary fiber could affect digestion by inhibiting proteolytic pancreatic enzymes.

Comparison of the effect of cell wall and hull fiber from canola and soybean on the bioavailability for rats of minerals, protein and lipid

Hull or cell wall material, isolated from canola (Brassica napus cv. Regent) or soybean (Glycine max) or cellulose was added to a basal, semipurified diet at a level of 12% and fed to growing male Wistar rats. The apparent availability of Cu, Fe, Ca, P and protein were lower when the fiber-containing diets were fed compared to the control diet. The availability of Mg was lower when the canola hull (CH) and cellulose (CE) diets were fed, whereas Zn availability was lower when the canola cell wall (CCW) and CE diets were fed, compared to the control diet. Determination of the feed transit time, by using the unabsorbable marker Cr2O3, demonstrated that the CE and soybean cell wall (SCW) diets had the fastest transit rates, followed by the CH, soybean hull (SH), CCW and control diets. Determination of the in vitro binding of the various fibers to metal ions demonstrated that CH was the strongest chelator, whereas CE had the lowest binding affinity for any of the minerals tested. At the termination of the trial, intestinal segments were removed and the in vitro mucosal transport of Cu, Fe, Mn and Zn were compared. The CCW diet consistently demonstrated lower transport for the four minerals, especially in the ileal segment.

Dietary fibers and supplementary iron in a milk replacer for veal calves

Thirty 1-wk-old male Holstein calves were allotted randomly to six groups into a 3 X 2 factorial design. The control diet was skim milk, whey, tallow, vitamins, and minerals. Either Alpha-Floc or pectin was added at 5% dry matter. Supplementary iron was added at 30 and 50 ppm (dry basis). The six diets were fed for 14 wk. Calves without supplementary iron were mildly anemic at 6 wk and severely at 14 wk (7 and 5 g/dl hemoglobin). At 14 wk, both fibers had decreased blood hemoglobin in calves given supplementary iron. Feed refusal began at 8 wk with the appearance of anemia for calves unsupplemented with iron, but both Alpha-Floc and pectin decreased feed refusal. Supplementary iron practically eliminated feed refusal. Supplementary iron improved average daily gain and feed conversion, but dietary fibers had no effect. Adding Alpha-Floc and pectin to the diets reduced frequency of diarrheic feces. Mean carcass weight of calves fed supplementary iron was 11.6% higher than that of unsupplemented calves. Supplementary iron decreased liver lipids and increased glutamic oxaloacetic transaminase activity in blood plasma.