Apple polyphenol-rich drinks dose-dependently decrease early-phase postprandial glucose concentrations following a...

Area of Science:

• Nutrition Science
• Human Physiology
• Pharmacology

Background:

• Previous studies indicated high-dose phlorizin-rich apple extract (AE) inhibits postprandial glycemia.
• The efficacy of lower AE doses on early-phase glycemia remained unclear.

Purpose of the Study:

• To evaluate the effect of lower doses of phlorizin-rich AE on early-phase postprandial glycemia in healthy adults.
• To investigate the underlying mechanisms of AE's action on glucose metabolism.

Main Methods:

• A randomized, controlled, double-blinded, cross-over trial involving healthy adults.
• Administration of drinks with varying doses of AE (0, 0.9, 1.35, 1.8 g) before a starch/sucrose meal.
• Measurement of postprandial glucose, insulin, C-peptide, GIP, and polyphenol metabolites; assessment of gastric emptying and urinary glucose excretion; in vitro intestinal glucose transport assays.

Main Results:

• All AE doses significantly reduced early plasma glucose incremental area under the curve (iAUC 0-30 min) compared to control.
• AE administration delayed the time to maximum glucose concentration (Tmax) but did not affect peak concentration (Cmax).
• Dose-dependent effects were observed for insulin, C-peptide, and GIP; in vitro studies showed reduced glucose uptake by AE.

Conclusions:

• Phlorizin-rich AE, even at low doses, demonstrates a capacity to slightly delay early-phase postprandial glycemia.
• The extract influences early glucose absorption and hormonal responses without altering peak or total glycemic outcomes.
• AE's effects are mediated by polyphenol metabolites and direct impact on intestinal glucose transport.