Digestion and physiological properties of resistant starch in the human large bowel

Abstract

The digestion of four sources of resistant starch (RS) has been studied in twelve healthy volunteers who ate controlled diets for 15d periods. RS from potato, banana, wheat and maize (17-30g/d) was compared with a starch-free diet, a diet containing wheat starch that was fully digested in the small intestine, and with 18.4 g NSP from bran/d. RS increased stool wet weight by 1.6 g/d per g RS fed for potato, 1.7 for banana, 2.5 for wheat and 2.7 for maize, but this was significantly less than bran NSP at 4.9 g/g. RS was extensively digested in twenty-seven of thirty-four diet periods but five subjects were unable to break down one or two of the RS sources. Faecal N and energy excretion were increased. RS decreased NSP breakdown and RS, (resistant starch granules) tended to prolong transit time. All forms of RS increased faecal total short-chain fatty acid excretion. RS, (from potato and banana) gave greater proportions of acetate in faeces, and RS, (retrograded starch from wheat and maize) more propionate. We have concluded that RS, and RS, are broken down in the human gut, probably in the colon although in 26% of cases this breakdown was impaired. RS exerts mild laxative properties, predominantly through stimulation of biomass excretion but also through some sparing of NSP breakdown.

Dietary intake and faecal excretion of carbohydrate by Australians: importance of achieving stool weights greater than 150 g to improve faecal markers relevant to colon cancer risk

“…Dietary ®bre intake was negatively correlated with transit time (Table 3). The effects of dietary ®bre on faecal bulking and transit time are well known (Burkitt et al, 1972;Cummings et al, 1978;Kelsay et al, 1978;Davies et al, 1986;Lupton et al, 1993). Dietary intake of NSP alone did not signi®cantly correlate with changes in transit time, but became signi®cant when combined with RS (Table 3).…”

“…In addition to NSP, the other major carbohydrate to reach the colon undigested is starch (Englyst & Cummings, 1990). Undigested starch, named resistant starch (RS), has been shown recently by us (Phillips et al, 1995;Birkett et al, 1996) and others (Scheppach et al, 1988a;Van Munster et al, 1994;Cummings et al, 1996) to impact signi®cantly upon colonic function.…”

Vinegar dressing and cold storage of potatoes lowers postprandial glycaemic and insulinaemic responses in healthy subjects

“…RS in the form of resistant potato starch has been shown to promote comparatively high yields of butyric acid upon colonic fermentation compared with other sources of indigestible carbohydrates, as judged from butyric acid analysis in human faeces and caecum and colon in pigs, respectively (Cummings et al, 1996;Martin et al, 1998). Cold storage and addition of vinegar also significantly lowered glycaemic and insulinaemic excursions to a potato meal.…”

A new look at dietary carbohydrate: chemistry, physiology and health

“…Intestinal bacteria are eventually excreted in faeces, and thus contribute to the laxative properties of high NSP diets. In fact, all carbohydrates which reach the large intestine will have a laxative effect, although some are better laxatives than others (Cummings, 1993;Cummings et al, 1996;Munster et al, 1994;Phillips et al, 1995).…”

“…The concentrations of glucose and fructose in blood are also important in determining protein glycosylation and possibly the process of ageing (Brownlee et al, 1988;Dills, 1993;McDonald, 1995). Some starches affect large bowl function (Cummings et al, 1996;Munster et al, 1994;Phillips et al, 1995) and the concept of resistant starch (RS) has been developed (Englyst et al, 1992). Recently the importance of a previously neglected group of carbohydrates, the oligosaccharides, has emerged with the demonstration that some are fermented in the colon and selectively stimulate the growth of speci®c intestinal bacteria thought to be bene®cial to health Gibson & Roberfroid, 1995;Hidaka et al, 1986).…”