. 2020 Oct 16;12(10):3169. doi: 10.3390/nu12103169

Table 7.

Clinical studies with flavonoids effect in diabetes and diabetic retinopathy (DR).

Study	Participants	Dose	Duration	Results	Reference
Contribution of flavonoid intake for decreasing the risk of development chronic diseases	n = 10,054, of which 546 were addressed to measure the risk of developing diabetes	N/A	1 year	↓ risk of developing T2DM associated with higher quercetin and myricetin intake	[127]
Green tea catechins impact, with or without caffeine, on glycemic control markers	n = 1584 out of twenty-two eligible trials	N/A	N/A	↓ FBG levels	[128]
	n = 1584 out of twenty-two eligible trials	N/A	N/A	No significant difference in FBI, HbA1c and HOMA-IR	[128]
Orally administered combination of flavonoids with Centella asiatica and Melilotus effect for the treatment of CME without macular thickening	n = 70 with T2DM and CME without macular thickening	Oral combination of 300 mg diosmin, 15 mg C. asiatica and 160 mg Melilotus per day	36 months	↑ retina sensitivity	[129]
	n = 70 with T2DM and CME without macular thickening		36 months	No differences in visual acuity, mean central retinal thickness, stability fixation, HbA1c percentage, microalbuminuria and blood pressure	[129]
Purified anthocyanins effect to increase serum adiponectin	n = 160 prediabetic or newly diagnosed diabetic	2 × 320 mg per day	12 weeks	Anthocyanins supplementation increased serum adiponectin and decreased fasting glucose in newly diagnosed diabetics but not in prediabetic patients	[130]
Chinese green tea consumption and the risk of diabetic retinopathy	n = 100 with DR	Drink Chinese green tea for at least once a week	1 year	↓ 50% risk of developing DR in people who regularly drink green tea than those who do not	[132]
	n = 100 diabetic without DR	Drink Chinese green tea for at least once a week	1 year		[132]
Pycnogenol^® effect on the progression of visual acuity	n = 1169 with T1DM and T2DM that presented DR	60–120 mg per day	6 months	↓ progression of visual loss	[133,134]
Pycnogenol^® effect on the progression of visual acuity	n = 1169 with T1DM and T2DM that presented DR	60–120 mg per day	6 months	No significant improvements in patients’ sight	[133,134]
Effect of Pycnogenol^® in early stages of DR	n = 46 diagnosed with moderate degree of diabetic macular edema	150 mg daily	2 months	Visual and baseline improvement	[134]
Flavonoid-rich diet impact on DR and diabetes-related biomarkers	n = 381 diabetic patient from NHANES 2003–2006	N/A	N/A	↓ risk of developing DR by 30%	[131]
	n = 381 diabetic patient from NHANES 2003–2006	N/A	N/A	↓ C-reactive protein levels, HbA1C and glucose	[131]
Effects of antioxidant supplementation in ROS circulating levels and in changes in CMT	n = 68 with NPDR	One tablet containing 50 mg of pycnogenol, 30 mg of Vitamin E and 20 mg of CoQ per day	6 months	↓ ROS levels and CMT	[135]

CME: cystoid macular edema, CMT: central macular thickness, CoQ, coenzyme Q10, DR: diabetic retinopathy, FBG: fasting blood glucose, FBI: fasting blood insulin, HbA1c: glycated hemoglobin, HOMA-IR: homeostatic model assessment of insulin resistance, N/A: not applicable, NHANES: National Health and Nutrition Examination Survey, NPDR: non-proliferative diabetic retinopathy, ROS: reactive oxygen species, T1DM: type 1 diabetes mellitus, T2DM: type 2 diabetes mellitus, ↑: increase, ↓ decrease.