Biography
Biography: John A Monro
Abstract
The glycaemic response to ingested carbohydrate foods is governed partly by gut-level processes of digestion that may be affected by digestion-resistant food remnants. Such processes include gastric emptying, luminal mixing, diffusion,
and enzymic depolarisation. Freed from the constraint of fruit structure, after in vitro digestion of kiwi fruit flesh the settled volume of dispersed kiwifruit debris was four times the flesh volume before digesting, and enough to occupy a large proportion of the free space within the foregut. The impact of kiwifruit remnants on gut processes involved in the glycaemic response to co-ingested carbohydrate foods was tested in vitro by measuring glucose diffusion, mixing, and pancreatic digestion of carbohydrate staples within the settled dispersion of kiwifruit remnants. The additional effect of introduced hydrocolloid on
mixing in the presence of kiwi fruit remnants was also measured. Within the settled dispersion of kiwifruit debris glucose diffusion was reduced by about 40%, simulated intraluminal mixing was reduced by about 50%, and digestion was retarded. Hydrocolloid substantially accentuated the retardation of mixing by kiwifruit remnants. In a subsequent clinical trial meals were formulated to be equal in carbohydrate content and type, but contain cereal plus kiwifruit, or cereal plus kiwifruit sugars, so any differences in meal effects could be attributed to non-available carbohydrate components of the kiwifruit. The meals containing kiwifruit suppressed the glycaemic response to co-ingested wheaten cereal, averted hyperglycaemia, and maintained satiety. The results suggest that dietary fibre from kiwifruit may significantly suppress the glycaemic response to co-ingested carbohydrate through its effects on physical processes in the gut that are part of digestion, and indicate a need for further research to clarify its role.