Polyphenol- and fibre-rich dried fruits with green tea attenuate starch-derived postprandial blood glucose and insulin: a randomised, controlled, single-blind, cross-over intervention.
Polyphenol- and fibre-rich foods (PFRF) have the potential to affect postprandial glycaemic responses by reducing glucose absorption, and thus decreasing the glycaemic response of foods when consumed together. A randomised, single-blind, cross-over study was conducted on sixteen healthy volunteers to test whether PFRF could attenuate postprandial blood glucose in healthy volunteers when added to a source of carbohydrate (starch in bread). This is the first study to examine the effects of a meal comprised of components to inhibit each stage of the biochemical pathway, leading up to the appearance of glucose in the blood. The volunteers were fasted and attended four visits: two control visits (bread, water, balancing sugars) and two test visits (single and double dose of PFRF) where they consumed bread, water and PFRF. Blood samples were collected at 0 (fasted), 15, 30, 45, 60, 90, 120, 150 and 180 min after consumption. The PFRF components were tested for α-amylase and α-glucosidase inhibitory potential in vitro. Plasma glucose was lower after consumption of both doses compared with controls: lower dose, change in mean incremental areas under the glucose curves (IAUC)=-27·4 (sd 7·5) %, P<0·001; higher dose, IAUC=-49·0 (sd 15·3) %, P<0·001; insulin IAUC was also attenuated by-46·9 (sd 13·4) %, P<0·01. Consistent with this, the polyphenol components of the PFRF inhibited α-amylase (green tea, strawberry, blackberry and blackcurrant) and α-glucosidase (green tea) activities in vitro. The PFRF have a pronounced and significant lowering effect on postprandial blood glucose and insulin response in humans, due in part to inhibition of α-amylase and α-glucosidase, as well as glucose transport.
School of Food Science and Nutrition,University of Leeds,Leeds LS2 9JT,UK.
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H
Nyambe-Silavwe
School of Food Science and Nutrition,University of Leeds,Leeds LS2 9JT,UK.
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G
Williamson
D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism*; D001939:Bread; D028241:Camellia sinensis / Q000737:chemistry*; D018592:Cross-Over Studies; D004043:Dietary Fiber / Q000494:pharmacology*; D031985:Fragaria / Q000737:chemistry; D005638:Fruit / Q000737:chemistry*; D064368:Healthy Volunteers; D006801:Humans; D007328:Insulin / Q000097:blood*; D010936:Plant Extracts / Q000494:pharmacology; D059808:Polyphenols / Q000494:pharmacology*; D019518:Postprandial Period; D031965:Ribes / Q000737:chemistry; D065856:Rubus / Q000737:chemistry; D016037:Single-Blind Method; D013213:Starch / Q000097:blood; D013662:Tea / Q000737:chemistry; D000516:alpha-Amylases / Q000378:metabolism; D000520:alpha-Glucosidases / Q000378:metabolism
D001786:Blood Glucose; D004043:Dietary Fiber; D007328:Insulin; D010936:Plant Extracts; D059808:Polyphenols; D013662:Tea; D013213:Starch; D000516:alpha-Amylases; D000520:alpha-Glucosidases
   α-Amylase;  α-Glucosidase; Diabetes; Fibre; GI glycaemic index; IAUC incremental areas under the glucose curves; IC50
                concentration required for 50 % inhibition; PFRF polyphenol- and fibre-rich food; Polyphenols; Postprandial glucose