Composition, intake, and excretion of fiber constituents

Extract: The role of fiber in human diet in preventing a number of chronic diseases has been a widely debated topic in recent years. The claim that populations at low risk for colon cancer generally consume a more fiber-rich diet than those at high risk, has been used to postulate a protective role for this group of substances. In this study, the question whether populations leading different dietary lifestyles and who are at varying risks for colon cancer show marked differences in their dietary and fecal profiles of various fiber components was asked. Four study groups consisting of Seventh-day Adventist (SDA) pure vegetarians, SDA lacto-ovo vegetarians, SDA nonvegetarians, and a group of general population nonvegetarians were selected from the greater Los Angeles Basin area. Three-day composite diets and stools were analyzed for neutral detergent fiber (NDF), hemi-cellulose, lignin, cellulose, cutin plus silica, and pectin. The percentage composition and the daily intake and output of each of these components were computed for each population group. The dietary profile revealed a trend (not statistically significant) toward generally higher daily intake values among the vegetarian subgroups, neutral detergent fiber values in g/day: SDA pure vegetarians, 63.0; SDA-lacto-ovo vegetarians, 55.8; SDA nonvegetarians, 57.2; general population nonvegetarians, 52.5; lignin, cellulose, and pectin being the major contributors to this difference. In sharp contrast, in the stools, 24-hour excretion values for NDF decreased steadily in the order, SDA-pure vegetarians, SDA-lacto-ovo vegetarians, SDA-nonvegetarians, and general population nonvegetarians (NDF values in stools in g/day: SDA-pure vegetarians, 13.8; SDA-lacto-ovo vegetarians, 10.5; SDA-nonvegetarians, 8.19; and general population nonvegetarians, 5.05). This decrease paralleled a similar drop in dry stool weight (bulk) of stools. The observations generally indicate that introduction of meat into the daily diet significantly enhances the ability of intestinal microorganisms to degrade fiber components, as reflected by the lower excretion of NDF and its constituents. From the results of the present study it is concluded that under conditions of comparable intake of NDF the differences in fecal output of fiber components among the SDA and general population are a reflection of qualitative differences in the sources of plant fiber in the diet together with similar changes in microbial metabolism. (author)