Table A2.

Preclinical studies mentioned in the manuscript, study design, main objectives, and findings.

	Design	Main Objectives	Main Findings
Shamloo M et al. [30]	Experimental on cellular cultures.	Effects of Phenolic acids extracted from whole grains on glucose uptake in human Caco-2E cells	Glucose uptake inhibition was positively associated with the phenolic acids content.
Castro-Acosta ML et al. [35]	Double blind, crossover trial in 25 healthy subjects and in vitro study of possible mechanism.	Evaluate the effects of Apple and blackcurrant polyphenols rich drinks versus placebo on post-prandial glucose and incretin response to meal in humans.	Apple Polyphenols reduce postprandial insulin, C-Peptide and insulin area under the curve at 30 min.
Prpa E J et al. [36]	Double blind, crossover acute trial in 34 healthy subjects an in vitro study of possible mechanism.	Evaluate the effect of Apple Extract (with different content of polyphenols and phlorizin) vs. placebo on post-prandial glucose. Test the capacity of Apple Extract to inhibit cellular glucose transport	Polyphenol enriched apple extract reduced plasma glucose and insulin area under the curve at 30 min. In vitro model apple extract inhibits cellular glucose uptake in a dose dependent manner.
Xiao D. et al. [39]	Controlled three arm single-blinded, crossover randomized clinical trial in 32 adults with obesity and insulin resistance.	Evaluate the effect of red raspberry intake versus placebo on meal induced metabolic responses.	Compared to placebo Red raspberry reduced insulin area under the curve, peak glucose, peak insulin ad 2 h glucose area under the curve.
Paquette M, et al. [40]	Parallel double blind controlled and randomized trial in 41 overweight subjects	Evaluate the effect of strawberry and cranberry polyphenols consumption on insulin sensitivity, glucose tolerance and insulin secretion using the euglycemic iperinsulinemic clamp technique.	6 weeks consumption of strawberry and cranberry extract was associated to significant improvement in insulin sensitivity and insulin secretion.
Hsia DS, et al. [41]	Parallel double blind controlled and randomized trial in 35 overweight subjects	Evaluate the effect of cranberry consumption on insulin sensitivity, glucose tolerance and insulin secretion using the euglycemic iperinsulinemic clamp technique.	8 weeks consumption of cranberry extract has no effects on insulin sensitivity and insulin secretion.
Kerimi A. et al. [42]	double blind randomized, crossover, controlled trial in 16 healthy subjects	Evaluate versus placebo the acute effect of pomegranate juice and polyphenol rich extract from pomegranate on the bread derived postprandial blood glucose concentration.	Pomegranate polyphenols in beverage reduced post-prandial response to bread.
Ebrahimi-Mamaghani M et al. [49]	randomized controlled trial in 53 overweight woman with polycystic ovarian syndrome	Evaluate the effect of 8-week consumption of raw red onion consumption on metabolic features.	No effects of fasting glucose, modest cholesterol lowering activity.
Jafarpour-Sadegh F et al. [50]	parallel, triple blind controlled and randomized trial in 56 woman with breast cancer treated with doxorubicin.	Evaluate the effect of 8-week consumption of fresh yellow onion consumption on glucose metabolism.	Higher consumption of fresh yellow onion was associated with reduced fasting glucose and decreased insulin resistance.
Carnevale R et al. [58]	randomized, crossover, controlled trial in 30 subjects with prediabetes	Effects of 10 g extravirgin olive oil on post-prandial glucose and incretins	Extravirgin olive oil improved postprandial glucose an was associated with reduced activity of dipeptidyl-peptidase 4 and increased postprandial concentration of Glucagon Like Peptide 1
Chiva-Blanch G. et al. [60]	randomized, crossover, controlled trial in 67 subjects with high cardiovascular risk	Effects of 4 week consumption of dealcoholized red wine on glucose metabolism.	Consumption of dealcoholized red wine (with main content of polyphenols) reduced insulin resistance and fasting insulin.
Alves Ferreira M et al. [65]	double blind randomized, crossover, controlled trial in 120 non diabetic overweight woman	Evaluate effect of 12 week consumption of green tea versus 1 g metformin on glycemic control	Green tea consumption had similar effects to metformin on glycemic control.