Manipulation of starch bioaccessibility in wheat endosperm to regulate starch digestion, postprandial glycemia, insulinemia, and gut hormone responses: a randomized controlled trial in healthy ileostomy participants.
BACKGROUND
Cereal crops, particularly wheat, are a major dietary source of starch, and the bioaccessibility of starch has implications for postprandial glycemia. The structure and properties of plant foods have been identified as critical factors in influencing nutrient bioaccessibility; however, the physical and biochemical disassembly of cereal food during digestion has not been widely studied.


OBJECTIVE
The aims of this study were to compare the effects of 2 porridge meals prepared from wheat endosperm with different degrees of starch bioaccessibility on postprandial metabolism (e.g., glycemia) and to gain insight into the structural and biochemical breakdown of the test meals during gastroileal transit.


METHODS
A randomized crossover trial in 9 healthy ileostomy participants was designed to compare the effects of 55 g starch, provided as coarse (2-mm particles) or smooth (<0.2-mm particles) wheat porridge, on postprandial changes in blood glucose, insulin, C-peptide, lipids, and gut hormones and on the resistant starch (RS) content of ileal effluent. Undigested food in the ileal output was examined microscopically to identify cell walls and encapsulated starch.


RESULTS
Blood glucose, insulin, C-peptide, and glucose-dependent insulinotropic polypeptide concentrations were significantly lower (i.e., 33%, 43%, 40%, and 50% lower 120-min incremental AUC, respectively) after consumption of the coarse porridge than after the smooth porridge (P < 0.01). In vitro, starch digestion was slower in the coarse porridge than in the smooth porridge (33% less starch digested at 90 min, P < 0.05, paired t test). In vivo, the structural integrity of coarse particles (∼2 mm) of wheat endosperm was retained during gastroileal transit. Microscopic examination revealed a progressive loss of starch from the periphery toward the particle core. The structure of the test meal had no effect on the amount or pattern of RS output.


CONCLUSIONS
The structural integrity of wheat endosperm is largely retained during gastroileal digestion and has a primary role in influencing the rate of starch amylolysis and, consequently, postprandial metabolism. This trial was registered at isrctn.org as ISRCTN40517475.
Biopolymers Group, Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom;
Cathrina H
http://orcid.org/0000-0003-4952-0229
CH
Edwards
Biopolymers Group, Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom;
Myriam Ml
MM
Grundy
Biopolymers Group, Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom;
Terri
T
Grassby
Biopolymers Group, Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom;
Dafni
D
Vasilopoulou
Nutrition and Dietetic Research Group, Faculty of Medicine, Hammersmith Campus, Imperial College, London, United Kingdom.
Gary S
GS
Frost
Biopolymers Group, Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom;
Peter J
PJ
Butterworth
Biopolymers Group, Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom;
Sarah Ee
SE
Berry
Department of Gastroenterology, Guy's and St. Thomas' National Health Service Foundation Trust, London, United Kingdom; and.
Jeremy
J
Sanderson
Biopolymers Group, Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom; peter.r.ellis@kcl.ac.uk.
Peter R
PR
Ellis
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004063:Digestion; D056625:Endosperm / Q000737:chemistry*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000097:blood; D005768:Gastrointestinal Hormones; D064368:Healthy Volunteers; D006801:Humans; D007081:Ileostomy; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period; D013213:Starch / Q000737:chemistry*; D014280:Triglycerides / Q000097:blood; D014908:Triticum / Q000737:chemistry*; D055815:Young Adult
D001786:Blood Glucose; D002096:C-Peptide; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified; D005768:Gastrointestinal Hormones; D007328:Insulin; D014280:Triglycerides; D005749:Gastric Inhibitory Polypeptide; D013213:Starch
bioaccessibility; digestion; glycemia; ileostomy; postprandial; starch; structure