Changes to the quantity and processing of starchy foods in a western diet can increase polysaccharides escaping digestion and improve in vitro fermentation variables.

This study investigated how readily achievable changes to the quantity and processing of starchy foods in a typical Western diet: (1) were reflected in levels of resistant starch (RS) and NSP excreted from the small intestine; and (2) more favourable profiles of butyrate, NH3 and phenol production. Two diets, a low-starch diet (LSD) and a high-starch, low-fat diet (HSLFD) were compared. The LSD with 20% total energy (%E) from starch was based on a 'typical' Australian diet, while the HSLFD (40%E as starch) was the same Australian diet modified by an increased content of legumes, starchy foods and coarsely-ground cereals and by a reduced fat content. Four subjects with iliostomies consumed each diet for 2 d, with ileal effluent collection on the second day. On the HSLFD compared with the LSD, RS in ileal effluent increased from from 0.49 to 1.7 g/MJ per d (P < 0.005) while ileal NSP excretion increased from 2.0 to 3.3 g/MJ per d (P < 0.05). Ileal effluents obtained after each diet were incubated for 24 h in vitro with a human faecal innoculum. After fermentation, ileal effluent from the HSLFD produced more butyrate relative to other short-chain fatty acids (17.5 v. 15.8 molar %, P < 0.005) and less phenol (2.3 v. 5.7 mg/l, P < 0.05) and NH3 (20.3 v. 23.1 mmol/l, P < 0.005) than the LSD diet. The HSLFD also generated a lower pH (6.15 v. 6.27, P < 0.05). On a wt/wt basis, RS was 2.3-fold higher in the HSLFD effluent while NSP did not increase, suggesting that the change in RS largely contributed to the fermentation effects. Changes in in vitro variables when the HSLFD ileal effluent was ground before fermentation indicated the importance of physical structure in determining ileal excretion of RS. We conclude that: (1) readily achievable modifications to the amount and processing of starchy foods in an Australian diet would produce potential benefits for in vitro fermentation variables; and (2) the physical structure of grains and cereals is important in determining access by colonic bacteria to a carbohydrate substrate.

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.

OBJECTIVES: This study investigated, on 53 Australians consuming a typical Western diet, the relationship between dietary intake, faecal excretion of carbohydrate and changes in faecal markers believed to be relevant to colon cancer risk, for example faecal output, transit time and concentrations of phenols, ammonia and butyrate. DESIGN: Fifty-three subjects consuming their usual diet were asked to record and weigh all food consumed for a seven day period, and to collect faeces for three days during this period. SETTING: Geelong, Victoria, Australia. SUBJECTS: All volunteers were either staff and students of the university, or associates of the authors. INTERVENTIONS: None. RESULTS: Volunteers had the following dietary intakes of carbohydrate (g/d; mean +/- s.d.); starch 131 +/- 41 (including resistant starch (RS), 5 +/- 2), sugar 108 +/- 37 and non-starch polysaccharides (NSP) 14 +/- 7. Daily faecal output was 127 +/- 70 g and transit time 47 +/- 19 h. Analysis of faecal samples found 0.8 +/- 1.2 g RS and significant relationship with the concentration (mmol/L) of butyrate excreted n faeces (r = 0.34, P < 0.05). Dietary intake of RS was associated with higher concentrations of faecal ammonia (r = 0.34, P < 0.05), but this association was reversed when RS was combined with NSP in the diet (r = 0.07, NS). In contrast to dietary intake, the faecal excretion of RS was negatively related to faecal ammonia concentration (r = -0.40, P < 0.01) and positively related to faecal output (r = 0.64, P < 0.01). Individuals who consumed more NSP in their diet (19 +/- 7 g/d) excreted more than 150 g faeces per day and had higher quantities of faecal-RS and -NSP; faster transit times; higher concentrations of short chain fatty acids and lower concentrations of potentially harmful ammonia and phenols. CONCLUSIONS: The combination of RS and NSP in the colon may be required to achieve an optimal luminal environment conducive to 'colonic health'. The results also support the suggestion that faecal output (< or > 150 g/d) may provide a useful index of colon cancer risk. High faecal outputs are achieved through higher intakes of NSP (the major component of dietary fibre).

Simple high-performance liquid chromatographic analysis of phenol and p-cresol in urine and feces.

Previous reports which present methods of analysis of phenol and p-cresol by HPLC are usually designed for the detection of these compounds in urine, can be complicated by the use of uncommon equipment or additional techniques such as steam distillation or derivatisation, or concentrate on the detection of phenol rather than p-cresol. In this paper we report a simple method suitable for the analysis of phenol and p-cresol in both urine and feces, based upon extraction into ether following acid hydrolysis and UV detection.