Abstract
BackgroundLower post-prandial glucose (PPG) and insulin (PPI) responses to foods are associated with reduced diabetes risk and progression. Several plant extracts have been proposed to reduce PPG or PPI by inhibiting enzymes or transporters involved in carbohydrate digestion and uptake. This study evaluates a range of such extracts, consumed with a carbohydrate load, for their effects on PPG, PPI and indicators of (gastrointestinal) tolerance.MethodsInterventions were extracts of mulberry fruit (MFE, 1.5 g), mulberry leaf (MLE, 1.0 g), white bean (WBE, 3.0 g), apple (AE, 2.0 g), elderberry (EE, 2.0 g), turmeric (TE, 0.18 g), AE + TE, and EE + TE. Each of these 8 individual extracts or combinations were added to a rice porridge containing ~ 50 g available carbohydrate (control). In a within-subject (randomised, balanced incomplete block) design, individual subjects received the control and a subset of 4 of the 8 extracts or combinations. Participants were 72 apparently healthy adults (mean [SD] age 31.2 [5.5] yr, body mass index 22.1 [2.0] kg/m2). The primary outcome was the percentage change in 2-h PPG (positive incremental area under the curve) relative to control. Secondary measures were the 2-h PPI response, 7-h breath hydrogen, measures of gastrointestinal discomfort, and urine glucose.ResultsIn the 65 subjects who completed the control and at least one intervention treatment, additions of AE, MFE and MLE produced statistically significant reductions in PPG vs control (p < 0.05; mean effect − 24.1 to − 38.1%). All extracts and combinations except TE and WBE significantly reduced PPI (p < 0.01; mean effect − 17.3% to − 30.4%). Rises in breath hydrogen > 10 ppm were infrequent, but statistically more frequent than control only for MLE (p = 0.02). Scores for gastrointestinal discomfort were extremely low and not different from control for any treatment, and no glucosuria was observed.ConclusionsAdditions of AE, MFE and MLE to rice robustly reduced PPG and PPI. EE significantly reduced only PPI, while TE and WBE showed no significant efficacy for PPG or PPI. Breath hydrogen responses to MLE suggest possible carbohydrate malabsorption at the dose used, but there were no explicit indications of intolerance to any of the extracts.Trial registrationClinicalTrials.gov identifier NCT04258501. Registered 6 February 2020 - Retrospectively registered.
Highlights
Lower post-prandial blood glucose and insulin responses (PPG and Postprandial insulin (PPI), respectively) are associated with a lower risk of development and progression of diabetes and cardiovascular diseases in healthy populations as well as those withdiabetes [1,2,3,4]
Elderberry Extract 2.0 g (EE) significantly reduced only PPI, while Turmeric 0.18 g (TE) and WBE showed no significant efficacy for post-prandial glucose (PPG) or PPI
Breath hydrogen responses to MLE suggest possible carbohydrate malabsorption at the dose used, but there were no explicit indications of intolerance to any of the extracts
Summary
Lower post-prandial blood glucose and insulin responses (PPG and PPI, respectively) are associated with a lower risk of development and progression of diabetes and cardiovascular diseases in healthy populations as well as those with (pre-)diabetes [1,2,3,4]. An example would be ingredients that act preabsorptively, as natural sources of inhibitors of enzymes (α-amylase, α-glucosidase) or transporters (Sodium-glucose linked co-transporter 1 [SGLT1], Glucose transporter 2 [GLUT2]) involved in carbohydrate digestion and uptake These gut-based mechanisms have previously been proposed as potential intervention targets for managing rates of glucose availability from foods [7,8,9,10,11,12]. A variety of plant extracts or combinations have been reported to have in vitro activity against these (and other) targets, in some cases having data indicating clinical efficacy for glycemic control [13] Many of these may be available as supplements or used in traditional medicine. This study evaluates a range of such extracts, consumed with a carbohydrate load, for their effects on PPG, PPI and indicators of (gastrointestinal) tolerance
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