Effects of resistant starch on the colon in healthy volunteers: possible implications for cancer prevention

Abstract

Recent evidence suggests that resistant starch (RS) is the single most important substrate for bacterial carbohydrate fermentation in the human colon. During two 4-wk periods. 12 healthy volunteers consumed a controlled basal diet enriched with either amylomaize starch (55.2 +/- 3.5 g RS/d; high-RS diet) or available cornstarch (7.7 +/- 0.3 g RS/d; low-RS diet). Approximately 90% of the RS consumed disappeared during intestinal passage; increased fermentation was verified by elevated breath-hydrogen excretion. During the high-RS diet, fecal wet and dry weight increased 49% and 56%, respectively (P < or = 0.005), whereas stool water content did not change significantly. Fecal concentrations and daily excretion of short-chain fatty acids were not different in the two study periods. During the high-RS diet, bacterial beta-glucosidase activity decreased by 26% (P < or = 0.05). Fecal concentrations of total and secondary bile acids were significantly lower during the high-RS than during the low-RS period [a decrease of 30% (P < or = 0.05) and 32% (P < or = 0.01), respectively, in total and secondary bile acids] whereas concentrations of primary bile acids were unaffected by RS consumption. During the high-RS diet, fecal concentrations of total neutral sterols decreased by 30% (P < or = 0.005) and fecal concentrations of 4-cholesten-3-one decreased by 36% (P < or = 0.05). These data suggest that RS has potentially important effects on bacterial metabolism in the human colon that may be relevant for cancer prevention.

Gastrointestinal responses following acute and medium term intake of retrograded resistant maltodextrins, classified as type 3 resistant starch

“…However, the results of the present study indicate an increased moisture content of the faeces with increasing RRM intake, which suggests that RRM moderately moisturizes faecal matter and affects bulk as has been shown in other studies (Phillips et al, 1995;Cummings et al, 1996). The latter has been identified as potentially beneficial for colonic mucosal health and the prevention of large bowel intestinal disorders, notably by reducing pH, increasing luminal contents of short-chainfatty acids, reducing luminal ammonia, secondary bile acids and faecal water toxicity (Tomlin and Read, 1990;Cummings et al, 1992;Van Munster and Nagengast, 1993;Birkett et al, 1997;Hylla et al, 1998;Topping and Clifton, 2001). …”

“…RS is supposed to contribute to colonic health through effects on gut flora, intestinal pH reduction, secondary bile acids reduction, elevated butyrate production and reductions in putrefactive protein fermentation as well as in luminal ammonia concentrations. Although these effects are generally supposed to beneficially impact on health, not all studies show a positive outcome on measured clinical endpoints (Edwards et al, 1995;Hylla et al, 1998;Topping and Clifton, 2001). Type 4 RS may differ in fermentation behaviour depending on its modified molecular structure.…”

Bioavailability of starch in bread rich in amylose: metabolic responses in healthy subjects and starch structure

“…However, the relationship of satiety to postprandial glycaemic response is not clear (Barkeling et al, 1995), and the satiating effect seems to be a complex process involving multiple factors . Escaping digestion in the small intestine, resistant starch fraction present in HAWB become a substrate for colonic fermentation with possible implication in cancer (Hylla et al, 1998). Resistant starch was suspected to produce a relative high production of butyrate (Martin et al, 1998), considered as a bene®cial substrate against colonic diseases.…”

Physiological aspects of energy metabolism and gastrointestinal effects of carbohydrates

“…Seven studies have reported accurate RS measurements in diet and have carried out adequate faecal collections (Table 6), from which it can be seen that the average increase in stool weight is 1.5 g/g RS fed. A meta-analysis including data from six of these seven studies (Tomlin and Read, 1990;van Munster et al, 1994;Phillips et al, 1995;Cummings et al, 1996;Silvester et al, 1997;Heijnen et al, 1998;Hylla et al, 1998) (excluding Tomlin and Read, 1990; because no error measurements are given in the paper) has been carried out and the results are given in Figure 6. This shows a highly significant overall increase in mean daily stool weight for the group of 41.1 g/day (75.4 g s.e.m.…”