Psyllium shifts the fermentation site of high-amylose cornstarch toward the distal colon and increases fecal butyrate concentration in rats

We examined the combination effects of psyllium (PS) and resistant starch o n large bowel short-chain fatty acids (SCFA): Rats were fed one of the foll owing four diets: low amylose (LAS) or high amylose cornstarch diets (HAS, 50 g/kg diet) with or without 15 g PS/kg diet (LAS/PS and HAS/PS diets). HA S and/or PS were substituted for the same amounts of LAS in diets. Cecal bu tyrate concentrations were significantly higher in rats fed the HAS and HAS /PS diets than in those fed the LAS and LAS/PS diets. However, butyrate and total SCFA concentrations in rats fed the HAS diet decreased along the len gth of the colon and fecal butyrate concentration was reduced to one-third of that in the cecum. In contrast, the HAS/PS diet maintained higher butyra te concentrations throughout the large bowel. Fecal butyrate concentration in the HAS/PS diet-fed group significantly exceeded the sum of the concentr ations in rats fed the LAS/PS and HAS diets. PS supplementation to the HAS diet significantly increased fecal starch excretion by 10 fold compared wit h that of rats fed the HAS diet. There was a positive correlation between f ecal butyrate concentration and fecal starch excretion (r = 0.709, P < 0.00 01). In a further experiment, ileorectostomized rats were fed the HAS and H AS/PS diets. From the difference in fecal starch excretion between normal a nd ileorectostomized rats, starch degradation by large bowel microflora in rats fed the HAS and HAS/PS diets was deduced to be 96% and 63%, respective ly. These findings support the hypothesis that PS may delay the fermentatio n rate of HAS in the cecum and shift the fermentation site of HAS toward th e distal colon, leading to the higher butyrate concentration in the distal colon and feces.