Biomedical subjects

J G Muir

Publications and source records attributed to J G Muir.

At least 19 recordsLinked to original sources

PubMed2007

Review article: fructose malabsorption and the bigger picture.

Fructose is found widely in the diet as a free hexose, as the disaccharide, sucrose and in a polymerized form (fructans). Free fructose has limited absorption in the small intestine, with up to one half of the population unable to completely absorb a load of 25 g. Average daily intake of fructose varies from 11 to 54 g around the world. Fructans are not hydrolysed or absorbed in the small intestine. The physiological consequences of their malabsorption include increasing osmotic load, providing substrate for rapid bacterial fermentation, changing gastrointestinal motility, promoting mucosal biofilm and altering the profile of bacteria. These effects are additive with other short-chain poorly absorbed carbohydrates such as sorbitol. The clinical significance of these events depends upon the response of the bowel to such changes; they have a higher chance of inducing symptoms in patients with functional gut disorders than asymptomatic subjects. Restricting dietary intake of free fructose and/or fructans may have durable symptomatic benefits in a high proportion of patients with functional gut disorders, but high quality evidence is lacking. It is proposed that confusion over the clinical relevance of fructose malabsorption may be reduced by regarding it not as an abnormality but as a physiological process offering an opportunity to improve functional gastrointestinal symptoms by dietary change.

Adolescent↗

PubMed2005

Reinforcing the mucus: a new therapeutic approach for ulcerative colitis?

Luminal delivery of phosphatidyl rich phospholipids appears to reduce mucosal inflammatory activity in a high proportion of patients with chronically active ulcerative colitis. The simplicity and apparent safety of this therapeutic approach offers new insights into the importance of the mucus barrier in the pathogenesis and treatment of ulcerative colitis.

Colitis, Ulcerative↗

PubMed2004

Arabinoxylan fibre improves metabolic control in people with Type II diabetes.

OBJECTIVE: To determine whether diet supplementation with arabinoxylan-rich (AX)-fibre from wheat improves glycaemic control in Type II diabetes. DESIGN: Randomized, crossover intervention trial. SETTING: Monash Medical Centre. SUBJECTS: A total of 15 subjects with Type II diabetes. INTERVENTIONS: Over two 5-week periods, subjects supplemented their usual diet with control bread and muffins (50% whole wheat, 50% white flour) (control diet) or with AX-bread and muffins (50% whole wheat, 36% white flour, 14% AX fibre) (AX diet). Subjects completed a 7-day food diary. At 0 and 5 weeks, venous blood was collected for determination of fasting and 2 h glucose, insulin, fructosamine and blood lipids. Blood pressure, body weight and body fat were also determined. A 24 h faecal sample, from 12 subjects, was weighed and analysed for faecal polysaccharide as a marker for dietary compliance. RESULTS: Control and AX diets were similar except the AX diet supplied an additional 15.1 (12.0-18.5) (mean (95% confidence intervals)) g/day dietary fibre (P=0.000). Consumption of the AX diet increased faecal output by 61.5 (0.2-122.8) g/day (P=0.05) on a wet weight basis and significantly lowered fasting and 2 h plasma glucose, 2 h insulin and serum fructosamine (P=0.002, 0.000, 0.015, and 0.02, respectively). Blood lipids, body weight, fat mass and blood pressure remained unchanged. CONCLUSION: A supplement of 15 g/day of AX-rich fibre can significantly improve glycaemic control in people with Type II diabetes.

Blood Glucose↗

PubMed2003

Dietary fibre: a roughage guide.

The concept of dietary fibre is a complex one that incorporates the physical and physiological functions of fibre and its effects both systemically and local to the gastro-intestinal tract. Dietary fibre can be usefully classified according to its solubility and fermentability, which allows rational clinical application. Fibres may act in several ways including by gel-forming effects in the stomach and small intestine, by its fermentation by colonic bacteria, by a 'mop and sponge' effect, and via concomitant changes in other aspects of the diet. These actions lead to potentially beneficial effects in the gastro-intestinal tract and systemically, such as lowering serum cholesterol and improving glycaemic control. Dietary fibre has been implicated in multiple clinical situations but, although an extensive literature on putative actions and proposed physiological bases is available, high-level evidence of efficacy is limited. Nevertheless, encouraging the intake of a high-fibre diet is likely to have a range of health benefits and physicians are encouraged to follow simple practical guidelines in their everyday practice.

Australia↗

PubMed2000

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.

Adolescent↗

PubMed2000

Arabinoxylan fiber, a byproduct of wheat flour processing, reduces the postprandial glucose response in normoglycemic subjects.

BACKGROUND: Arabinoxylan (AX) is the major component of dietary fiber in the cereal grains that make up a large proportion of our diet. However, the physiologic effect of AX is unknown. OBJECTIVE: The objective of this study was to determine whether AX improves postprandial glucose and insulin responses in healthy humans. DESIGN: AX-rich fiber was extracted from the byproduct of wheat-flour processing. Three isoenergic breakfasts, comprising bread, margarine, and jam, had 75 g available carbohydrate, 10 g protein, and 14 g fat and contained 0, 6, and 12 g AX-rich fiber, respectively. Fourteen healthy subjects consumed the 3 breakfast meals in random order on 3 mornings >/=3 d apart after an overnight fast. Blood was taken from the subjects at regular intervals over 2 h and was analyzed for glucose and insulin. The palatability of bread containing AX-rich fiber was compared with that of a control bread. RESULTS: Compared with the control meal containing 0 g AX-rich fiber, the peak postprandial glucose concentration after meals containing 6 and 12 g AX-rich fiber was significantly lower (6. 3 +/- 1.3 compared with 7.2 +/- 1.0 mmol/L, P < 0.01; 5.9 +/- 0.9 compared with 7.2 +/- 1.0 mmol/L, P < 0.001, respectively). The incremental area under the curve (IAUC) for glucose was 20.2% (95% CI: 5.8%, 34.7%; P < 0.01) and 41.4% (25.9%, 56.8%; P < 0.001) lower, whereas IAUC for insulin was 17.0% (2.0%, 32.1%; P < 0.05) and 32. 7% (18.8%, 46.6%; P < 0.001) lower, respectively. Bread containing AX-rich fiber was as pala as 50% whole-wheat bread when evaluated with sensory analysis by 30 volunteers. CONCLUSIONS: Postprandial glucose and insulin responses were improved by ingestion of AX-rich fiber. Further research is required to determine whether AX-rich fiber is of benefit to people with type 2 diabetes.

Adult↗

PubMed2000

Arabinoxylan fiber from a by-product of wheat flour processing behaves physiologically like a soluble, fermentable fiber in the large bowel of rats.

Arabinoxylan is a major dietary fiber component of many cereals. Its physiological effects in the colon are largely unknown. This study examined the effects of an arabinoxylan-rich fiber (AX) extracted from a by-product of wheat flour processing in the rat colon compared with well-characterized soluble/rapidly fermentable and insoluble/slowly fermentable fibers. Rats were fed diets containing no fiber (NF) or 100 g/kg of total dietary fiber from AX, guar gum (GG) or wheat bran (WB) for 4 wk. Cecal mass and short-chain fatty acid (SCFA) pool were significantly higher while pH was significantly lower in the fiber-supplemented groups, particularly in the AX and GG groups. The pattern of SCFA production in the cecum was altered; AX fiber was a good source for acetate while GG and WB favored propionate and butyrate production, respectively. Fecal output was 7-, 6- and 5-fold higher, respectively, in the AX, GG and WB than in the NF groups (P < 0.01). All epithelial proliferation indices (crypt column height, number of mitotic cells/crypt column and mitotic index) differed significantly across the groups in a descending order of AX > GG > WB > NF. Distal mucosal dipeptidyl peptidase IV activities, which indicate cell differentiation status, were significantly lower in fiber-supplemented groups than in the NF groups. Distal mucosal alkaline phosphatase activities, induced as a response to injury or stress, were significantly higher for the AX and GG groups than for the NF or WB groups (P < 0.001). These results indicate that AX fiber behaves like a rapidly fermentable, soluble fiber in the rat colon.

Animals↗

PubMed1999

Wheat bran affects the site of fermentation of resistant starch and luminal indexes related to colon cancer risk: a study in pigs.

BACKGROUND: Recent studies suggest that resistant starch (effective in producing butyrate and lowering possibly toxic ammonia) is rapidly fermented in the proximal colon; the distal colon especially would, however, benefit from these properties of resistant starch. AIMS: To determine whether wheat bran (a rich source of insoluble non-starch polysaccharides), known to hasten gastrointestinal transit, could carry resistant starch through to the distal colon and thus shift its site of fermentation. METHODS: Twenty four pigs were fed four human type diets: a control diet, or control diet supplemented with resistant starch, wheat bran, or both. Intestinal contents and faeces were collected after two weeks. RESULTS: Without wheat bran, resistant starch was rapidly fermented in the caecum and proximal colon. Supplementation with wheat bran inhibited the caecal fermentation of resistant starch, resulting in an almost twofold increase (from 12.9 (2.5) to 20.5 (2.1) g/day, p<0.05) in resistant starch being fermented between the proximal colon and faeces. This resulted in higher butyrate (133%, p<0.05) and lower ammonia (81%, p<0.05) concentrations in the distal colonic regions. CONCLUSIONS: Wheat bran can shift the fermentation of resistant starch further distally, thereby improving the luminal conditions in the distal colonic regions where tumours most commonly occur. Therefore, the combined consumption of resistant starch and insoluble non-starch polysaccharides may contribute to the dietary modulation of colon cancer risk.

Ammonia↗

PubMed1998

Modulation of fecal markers relevant to colon cancer risk: a high-starch Chinese diet did not generate expected beneficial changes relative to a Western-type diet.

In a randomized, crossover dietary intervention study, 12 Australians (of white descent) consumed a diet typical of low-income communities in China and an average Australian diet so that effects on fecal markers thought to be relevant to colon cancer risk could be compared. The Chinese diet contained 35.3 g starch/MJ daily [including 2 g resistant starch (RS)/MJ and 1.5 g nonstarch polysaccharides (NSPs)/MJ]; the Australian diet contained 12 g starch/MJ daily (including 0.8 g RS and 2.7 g NSPs/MJ). Subjects followed each diet for 3 wk. Serum cholesterol concentrations were significantly lower after the low-fat, high-starch Chinese diet than after the Australian diet (mean +/- SEM: 4.17 +/- 0.30 compared with 5.04 +/- 0.28 mmol/L, respectively, P < 0.05), a difference indicative of dietary compliance. Fecal pH was lower after the Chinese diet (6.51 +/- 0.04) than after the Australian diet (6.63 +/- 0.05; P < 0.05). For all other fecal markers examined, however, the Chinese diet produced less favorable changes, including lower fecal bulk (86 +/- 11 compared with 141 +/- 20 g wet wt/d, P < 0.01), slower transit through the gut (69 +/- 6 compared with 56 +/- 7 h, P = 0.06), lower fecal concentrations of short-chain fatty acids [72.8 +/- 7.3 compared with 98 +/- 7.6 mmol/L (including butyrate: 12.2 +/- 1.3 compared with 18.4 +/- 2.3 mmol/L), P < 0.05], and higher fecal concentrations of potentially damaging ammonia (540 +/- 50 compared with 450 +/- 40 mg/L, P < 0.01) and phenols (109.2 +/- 13.2 compared with 68.5 +/- 12.9 mg/L, P < 0.01). These results suggest that consumption of a high-starch diet alone is insufficient to reduce the risk of developing colon cancer.

Adult↗

PubMed1997

Detecting wakefulness in anaesthetised children.

PURPOSE: To investigate the suitability of the isolated forearm technique in detecting wakefulness in children aged 8 to 16 yr. METHODS: Forty-one healthy English speaking children were enrolled. Following intravenous induction of anaesthesia with 5-7 mg.kg-1 thiopentone iv, but before administration of 1-1.5 mg.kg-1 succinylcholine a pneumatic tourniquet was inflated to 50 mmHg above systolic pressure in order to isolate the non-cannulated forearm. Thereafter, anaesthesia was maintained with halothane 1.5-2.5% in nitrous oxide and oxygen. Following the muscle relaxant the patient was instructed to move the unparalyzed arm. Movement was checked at 30 sec intervals and if present on command, identified as wakefulness. RESULTS: Movement of the isolated forearm to command was observed in 19.5% of children. The youngest child to respond was five years old. CONCLUSION: The isolated forearm technique can be used to detect wakefulness during and immediately following tracheal intubation in children from the age of five years.

Adolescent↗

PubMed1997

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).

Adolescent↗

PubMed1996

Wheat bran suppresses potato starch--potentiated colorectal tumorigenesis at the aberrant crypt stage in a rat model.

BACKGROUND & AIMS: Starch that escapes digestion in the small intestine (resistant starch [RS]) may act similarly to nonstarch polysaccharides in the colon. The aim of this study was to examine the effect of raw potato starch alone and in combination with wheat bran on tumor development and precancer events in a rat model of colorectal cancer. METHODS: Three groups of rats received either a low-RS/low-fiber ("basic") diet, the basic diet containing raw potato starch as 20% of carbohydrate content, or the potato starch diet plus 10% of "wheat bran" fiber. Epithelial proliferation, aberrant crypt foci (ACF), and tumors were measured 6 and 20 weeks after a 10-week course of dimethylhydrazine. RESULTS: Rats on the potato starch diet had tumors more frequently and had larger tumors than rats consuming the wheat bran or basic diets. Parallel effects on the density of ACF were found 6 weeks after the carcinogen. Although epithelial proliferation was significantly enhanced by potato starch compared with the basic diet, the addition of wheat bran did not suppress this enhancement. CONCLUSIONS: This type-2 RS enhances epithelial proliferation, ACF density, and tumor formation. The addition of wheat bran to an RS-containing diet suppresses tumorigenesis, acting on events responsible for the formation of ACF but not the events controlling the hyperproliferative phase.

Analysis of Variance↗

PubMed1996

Body fat distribution and non-insulin-dependent diabetes: comparison of a fiber-rich, high-carbohydrate, low-fat (23%) diet and a 35% fat diet high in monounsaturated fat.

The effects of a fiber-rich, high-carbohydrate, low-fat (HCLF) diet and a modified-fat (MF) diet high in monounsaturated fat on body fat distribution were examined by dual-energy X-ray absorptiometry (DXA) in 16 subjects with non-insulin-dependent diabetes (NIDDM) during a randomized crossover study. Subjects lost similar amounts of body fat consuming the HCLF and MF diets (-0.83 +/- 0.37 and -0.87 +/- 0.40 kg, respectively) despite a marked difference in total fat consumption. With the MF diet, the ratio of upper- to lower-body fat (UF:LF) remained unchanged because fat was lost proportionately from the upper and lower body. In contrast, with the HCLF diet, a disproportionate loss of lower-body fat caused the UF:LF to increase. The effects of diet on regional body fat loss were significant (P < 0.05, two-factor repeated-measures ANOVA).

Absorptiometry, Photon↗

PubMed1995

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.

Chromatography, High Pressure Liquid↗

PubMed1995

Food processing and maize variety affects amounts of starch escaping digestion in the small intestine.

Two meals which differed greatly in resistant starch (RS) concentration, but otherwise had similar macronutrient composition (including nonstarch polysaccharides), were fed for breakfast to five subjects with ileostomies. The high-RS meal included bread made from high-amylose maize, uncooked green banana flour, and coarsely ground uncooked wheat. The low-RS meal contained bread made from low-amylose maize, cooked green banana flour, and cooked wheat. The effluent produced over 14 h was analyzed for the total amount of starch escaping digestion. In the low-RS meal 51.8 +/- 6.2 g (mean +/- SD) starch was consumed and 2.4 +/- 0.6 g recovered in the effluent, while for the high-RS meal a total of 52.7 +/- 8.8 g starch was fed and 19.9 +/- 5.2 g recovered in the effluent. The ileostomy results provided additional validation of an in vitro resistant starch assay. Scanning electron micrographs of effluent from one subject who consumed the high-amylose bread revealed that many intact starch granules escaped digestion in the small intestine.

Adult↗

PubMed1995

Resistant starch in the diet increases breath hydrogen and serum acetate in human subjects.

The colonic fermentation of two diets differing in amounts of resistant starch (RS) was studied. High- and low-RS diets were fed to eight healthy subjects in three meals for 1 d. Breath hydrogen and two blood samples were collected over a 28-h period. The high-RS diet provided 59.1 +/- 4.7 g (mean +/- SE) RS and the low-RS diet provided 5.2 +/- 0.4 g RS. Breath hydrogen and the average total serum acetate were significantly higher during the high-RS diet than during the low-RS diet: 34.1 +/- 4.7 and 23.9 +/- 3.9 ppm (P < 0.001) and 169.1 +/- 12.8 and 118 +/- 6.6 mumol/L (P < 0.01), respectively. Butyrate and propionate were also detected in serum samples. Although not statistically significant, there was a trend (P = 0.087) for butyrate to increase with the high-RS diet. Subjects reported greater gastrointestinal symptoms during the high-RS diet. These results suggest that RS may have effects comparable with those of some fermentable dietary fibers.

Acetates↗

PubMed1995

Effect of resistant starch on fecal bulk and fermentation-dependent events in humans.

This study investigated the effect of two diets, which differed in resistant starch (RS) concentration, on fecal bulk and fermentation-dependent events in 11 humans. Amounts of RS consumed were 5.0 +/- 0.4 and 39.0 +/- 3.0 g/d (mean +/- SEM) for the low- and high-RS diets, respectively. The two diets were fed for 3 wk each in a randomized crossover design. Fecal collections were made in the third week of each study period. The high-RS diet produced an increase (P < 0.01) in total fecal output (from 138 +/- 22 to 197 +/- 37 g/d) and lowered fecal pH (6.9 +/- 0.1 to 6.3 +/- 0.1). There were significant increases (P < 0.05) in the fecal concentrations and daily excretion of butyrate (+38% and +100%, respectively) and acetate (+26% and +72%, respectively) during the high-RS period. The fecal excretion (g/d) of nonstarch polysaccharides (NSP) also rose by 50% during the high-RS diet, suggesting that the presence of starch in the colon may affect the fermentation of NSP. Subjects reported an increase in flatulence and easier defecation. These results demonstrate that RS has a significant impact on putative markers of colonic health in humans.

Acetates↗

PubMed1995

Dietary composition, body weight, and NIDDM. Comparison of high-fiber, high-carbohydrate, and modified-fat diets.

OBJECTIVE: To examine the effects of a high-carbohydrate low-fat (HCLF) and a modified-fat (MF) diet on body weight and metabolic control in subjects with non-insulin-dependent diabetes mellitus (NIDDM) living at home. RESEARCH DESIGN AND METHODS: Twenty-four NIDDM patients followed HCLF and MF diets alternately and in random order for a 3-month period while at home, with a 1-month baseline and washout between diets. Before and after each diet, fasting glucose and lipids, HbA1c, blood pressure, and body weight were measured. Dietary preferences were assessed by questionnaire. RESULTS: Subjects consumed 50% of energy as carbohydrate and 23% as fat on the HCLF diet and 40% of energy as carbohydrate and 36% as fat (over half of which was monounsaturated fat) on the MF diet. Subjects lost weight on both HCLF and MF diets (mean loss 0.7 and 1.3 kg, respectively). Although the MF diet resulted in a small decrease in fasting glucose levels, there was no significant change in HbA1c. Similarly, there was no significant difference between the diets in changes in blood pressure or fasting blood lipids. Most subjects (65%) preferred the MF diet. CONCLUSIONS: Although the MF diet is not a low-fat diet, it did not appear to facilitate weight gain in subjects with NIDDM living at home. The MF diet provides an alternative for individuals unable to comply with HCLF diets.

Blood Glucose↗