A change in human faecal flora in response to inclusion of gum arabic in the diet

Abstract

1. Gum arabic is a water-soluble polysaccharide resistant to human gut enzymes and thus can be described as dietary fibre.2. Using a most-probable-number technique, estimates were made of total anaerobes and of gum-arabic fermenters in the faeces of a volunteer during a contro1 period and during addition of 10 g gum arabic/d to the diet. Using an enrichment technique, the principal bacteria able to utilize gum arabic as the only carbohydrate source were isolated and characterized. 3. Faecal samples were analysed for undegraded gum arabic and, following acid-hydrolysis, for total sugars. 4. The proportion of the faecal flora able to degrade the gum arabic polymer rose from an initial level of 6.5% to more than 50% during gum-arabic ingestion, and subsequently returned to the control level after ingestion ceased. The principal gum-arabic fermenters were species of Bucteroides and Bifdobucterium.5 . Undegraded gum arabic was not detected in any faecal sample nor were there significant differences in the level of total sugars in acid-hydrolysed faeces between gum arabic and control periods.6. The results presented indicate a direct and rapid change in faecal flora in response to a specific change in the diet of a human volunteer.Little change in human faecal flora has been detected following changes in diet (Moore et al. 198 1 ; Savage, 1982) and studies have been complicated by the differences in flora seen between individuals. It is possible, however, that although no gross changes in the species occur, the population may adapt to the presence of new substrates by a change in the biotypes present or in other ways.Dietary fibre, which has a marked effect on the function of the large intestine, increasing faecal weight and reducing transit time (Eastwood & Passmore, 1983), includes the plant gums widely used as thickening, gelling and emulsifying agents in the food industry. Previous work has shown that inclusion of guar gum in the diet of a human subject increased the total count of anaerobic bacteria in faeces (Bayliss & Houston, 1985).Gum arabic is the second most widely used gum in the food industry (Blenford, 1984) and as such forms part of the average Western diet, although at a low level. It is a highly water-soluble extract from Acacia senegal, and is a high-molecular-weight globular molecule with a backbone of D-galactopyranose units and complex side chains of D-galactose, L-arabinose, L-rhamnose and D-glucuronic acid. The in vivo effects of gum arabic in the diet have been demonstrated by McLean Ross et al. (1983), who showed that breath hydrogen increased in subjects who had eaten a diet containing gum arabic for 3 weeks but not in control subjects whose diet had not contained gum arabic. It seems likely that this increase reflected an adaptation of the microbial population of the human colon to the presence of the substrate. Therefore, the present study was carried out to determine whether a specific change in the diet of a human volunteer could lead to a change in faecal flora or in that part of the flo...

Nutritional and Digestive Challenges to Being a Gum-Feeding Primate

“…A longer retention time in the gut would aid gum digestion; thus larger animals should be better able to digest gum. Humans appear to completely digest gum arabic (McLean Ross et al 1983;Wyatt et al 1986). Thus, for large primate species the challenge gum presents as a food is likely more regarding the quantity that can be obtained and not its digestive difficulties.…”

Indigestible Components of Grape Seeds Modify Cecal Enzyme Activity in Rats

“…The end-fermentation products, the growth of the bacteria mass and the water-holding capacity of the nonfermented compounds could contribute to increasing the bulking in the intestine. Some studies [19,20] suggest that the cecum enlarges to accommodate the tendency of residual material to accumulate within it [19]. The microflora as a whole has a trophic effect on the epithelium which can lead to a faster turnover rate, and this effect may be increased by the action of short-chain fatty acids from colonic fermentation, in particular butyric acid, which are considered lumen trophic factors [20].…”

“…Some studies [19,20] suggest that the cecum enlarges to accommodate the tendency of residual material to accumulate within it [19]. The microflora as a whole has a trophic effect on the epithelium which can lead to a faster turnover rate, and this effect may be increased by the action of short-chain fatty acids from colonic fermentation, in particular butyric acid, which are considered lumen trophic factors [20]. GSIF affected intestinal tissue, leading to hyperplasia of the colonic mucosa and increased wall thickness in the cecum (table 2).…”

“…GSIF affected intestinal tissue, leading to hyperplasia of the colonic mucosa and increased wall thickness in the cecum (table 2). The accumulation of fermentation products as well as the increase in residual material reaching the large bowel play a role in regulating both cellular metabolism as well as cell proliferation [19,20].…”

Fermentation of green alga sea-lettuce (Ulva sp) and metabolism of its sulphate by human colonic microbiota in a semi-continuous culture system

“…In humans, when gum arabic was included in the diet for 18 days, the proportion of the faecal flora able to degrade this substrate progressively rose from 6.5 to more than 50%. After the fibre was withdrawn from the diet, the proportion of gum arabic fermenting bacteria returned to the level present before ingestion (Wyatt et al, 1986). More recently, the necessity of adaptation of human subjects to xanthan gum, for their faecal microflora to achieve maximum hydrogen and SCFA production, was also demonstrated (Daly et al, 1993).…”