Table 1.
Baseline characteristics of the included trials.
| Author,year | Group | Sample size | Intervention | Dosage and composition | Singly-used flavonoids or mixtures | Principal subclasses of flavonoids | Route of Administr-ation | Duration | Mean age (year) | Sex(M/F) | BMI (kg/m2) | Study Population | IR measure |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Aubertin-leheudre, 2007 (13) | T | 25 | Isoflavone | Four capsules daily; each capsule contained 17.5 mg of isoflavones | Singly-used flavonoids | Isoflavones | Taking capsules | 12 m | 57.0 ± 5.0 | 0/25 | 30.0 ± 5.0 | Obese postmenopausal women | QUICKI |
| C | 25 | Placebo | A matched placebo | 58.0 ± 5.0 | 0/25 | 30.0 ± 2.0 | |||||||
| Aubertin-leheudre, 2008 (14) | T | 25 | Isoflavone | Four capsules daily; each capsule contained 17.5 mg of isoflavones | Singly-used flavonoids | Isoflavones | Taking capsules | 6 m | 57.1 ± 5.6 | 0/25 | 31.2 ± 4.5 | Obese postmenopausal women | HOMA-IR |
| C | 25 | Placebo | 57.7 ± 5.2 | 0/25 | 32.8 ± 4.8 | ||||||||
| Bell, 2011 (15) | T | 11 | Glavonoid™ | 300 mg/day (taken in 3 capsules with the evening meal); Glavonoid™ is standardized to 30% licorice glabra polyphenol and 3% glabridin | Mixtures | Isoflavones | Taking capsules | 8 w | 28.4 ± 2.8 | / | 29.4 ± 1.3 | Overweight and grade I-II obese subjects | HOMA-IR |
| C | 11 | Placebo | 25.7 ± 1.8 | / | 30.2 ± 1.2 | ||||||||
| Bogdanski, 2012 (16) | T | 28 | EGCG | One capsule with their morning meal; the capsules contained 379 mg of green tea extract (including 208 mg of EGCG) | Singly-used flavonoids | Flavan-3-ols | Taking capsules | 3 m | 49.2 ± 8.8 | 13/15 | 32.5 ± 3.3 | Obese hypertensive subjects | HOMA-IR |
| C | 28 | Placebo | One capsule of pure microcrystalline cellulose | 51.5 ± 7.4 | 15/13 | 33.9 ± 2.3 | |||||||
| Brown, 2009 (17) | T | 46 | EGCG | 400 mg bid daily | Singly-used flavonoids | Flavan-3-ols | Taking capsules | 8 w | 52.2 ± 6.4 | 46/0 | 31.2 ± 2.8 | Overweight and obese male subjects | HOMA-IR |
| C | 42 | Placebo | A matched placebo | 50.6 ± 6.5 | 42/0 | 31.0 ± 2.5 | |||||||
| Brüll, 2017 (18) | T | 68 | Quercetin | Three capsules per day (162 mg daily), one capsule with each principal meal | Singly-used flavonoids | Flavonols | Taking capsules | 18 w | 47.4 ± 10.5 | 34/34 | 31.1 ± 3.4 | Overweight−to−obese patients with (pre−) hypertension | HOMA-IR |
| C | 68 | Placebo | A matched placebo | 47.4 ± 10.5 | 34/34 | 31.1 ± 3.4 | |||||||
| Choquette, 2011 (19) | T | 23 | Isoflavones | The 70 mg daily dose of isoflavones contained 44 mg of daidzein, 16 mg of glycitein and 10 mg of genistein | Singly-used flavonoids | Isoflavones | Taking capsules | 6 m | 58.0 ± 5.0 | 0/23 | 29.2 ± 2.4 | Overweight-to-obese postmenopausal women | HOMA-IR |
| C | 22 | Placebo | The placebo capsules contained cellulose only | 59.0 ± 6.0 | 0/22 | 31.0 ± 2.9 | |||||||
| Cicero, 2019 (20) | T | 30 | Low-dose bergamot extract | Two pills at bedtime daily. The high‐dose group was given two boxes containing active treatment (bergamot extract (120mg flavonoids/pill)), and the low‐dose group was given one box containing active treatment and another one containing placebo | Mixtures | Multiple subclasses | Taking pills | 24 w | 43.0 ± 4.0 | 17/13 | 26.8 ± 1.7 | Overweight dyslipidemic subjects | HOMA-IR |
| T | 30 | High-dose bergamot extract | 45.0 ± 4.0 | 14/16 | 26.5 ± 1.9 | ||||||||
| C | 30 | Placebo | Two boxes both containing placebo pills | 44.0 ± 2.0 | 14/16 | 27.0 ± 1.8 | |||||||
| Davison, 2008 (21) | T | 12 | High dose-flavanol | 902 mg flavanols daily | Singly-used flavonoids | Flavan-3-ols | Drinking beverage | 12 w | 45.3 ± 4.4 | 4/8 | 32.8 ± 1.1 | Overweight and obese subjects | HOMA-IR |
| C | 11 | Low dose-flavanol | 36 mg flavanols daily | 44.4 ± 4.4 | 3/8 | 34.5 ± 1.8 | |||||||
| Dostal, 2015 (22) | T | 117 | EGCG | Four green tea extract capsules containing 1315 ± 116 mg total catechins per day (843 ± 44 mg as EGCG) | Singly-used flavonoids | Flavan-3-ols | Taking capsules | 12 m | 60.9 ± 0.5 | 0/117 | 28.5 ± 0.3 | Overweight and obese postmenopausal women | HOMA-IR |
| C | 120 | Placebo | A matched placebo | 60.6 ± 0.5 | 0/120 | 27.9 ± 0.3 | |||||||
| Guevara-Cruz, 2020 (23) | T | 22 | Genistein | 50 mg/day | Singly-used flavonoids | Isoflavones | Taking capsules | 2 m | 42.6 ± 1.9 | / | 34.6 ± 0.9 | Obese subjects | HOMA-IR |
| C | 23 | Placebo | A matched placebo | 43.0 ± 2.28 | / | 34.5 ± 1.0 | |||||||
| Hsu, 2008 (24) | T | 41 | Green tea extract | One capsule (400 mg) three times daily | Singly-used flavonoids | Flavan-3-ols | Taking capsules | 12 w | 43.0 ± 11.1 | 0/41 | 31.2 ± 3.5 | Obese women | HOMA-IR |
| C | 37 | Placebo | 400 mg cellulose three times daily | 43.9 ± 12.6 | 0/37 | 30.5 ± 4.6 | |||||||
| Hsu, 2011 (25) | T | 35 | Green tea extract | One capsule 30 minutes after meals three times daily; capsules contained 500 mg decaffeinated green tea extract | Singly-used flavonoids | Flavan-3-ols | Taking capsules | 16 w | 50.5 ± 9.2 | 12/23 | 30.3 ± 4.3 | Obese type 2 diabetics | HOMA-IR |
| C | 33 | Placebo | Pure microcrystalline cellulose | 52.2 ± 9.1 | 12/21 | 29.2 ± 3.6 | |||||||
| Khorshidi, 2018 (26) | T | 39 | Quercetin | 1,000 mg daily | Singly-used flavonoids | Flavonols | Taking capsules | 12 w | 29.5 ± 4.2 | 0/39 | 29.6 ± 3.7 | Overweight or obese women with polycystic ovary syndrome | HOMA-IR |
| C | 39 | Placebo | A matched placebo | 30 ± 5.5 | 0/39 | 28.6 ± 4.1 | |||||||
| Kirch, 2018 (27) | T | 47 | (–)-epicatechin | 25 mg daily | Singly-used flavonoids | Flavan-3-ols | Taking capsules | 7 w | Males: 36.0 ± 12.0; Females: 35.0 ± 16.0 |
25/22 | Males: 34.3 ± 6.2; Females: 31.2 ± 4.8 |
Overweight or obese subjects with metabolic syndrome | HOMA-IR |
| C | 47 | Placebo | A matched placebo | Males: 36.0 ± 12.0; Females: 35.0 ± 16.0 |
25/22 | Males: 34.3 ± 6.2; Females: 31.2 ± 4.8 |
|||||||
| Martin, 2019 (28) | T | 26 | Tart cherry juice | 240 mL daily. Tart cherry juice contained 65 mg anthocyanins/L (15.6 mg/240 mL) and 33.6 g total phenolics/L (993.6 mg/240 mL) | Mixtures | Multiple subclasses | Drinking beverage | 12 w | 41.0 ± 11.0 | 8/18 | 31.3 ± 6.0 | Overweight and obese adults | HOMA-IR; QUICKI |
| C | 26 | Placebo | 240 mL/day; no concentrations of anthocyanins or phenolics | 41.0 ± 11.0 | 8/18 | 31.3 ± 6.0 | |||||||
| Mielgo-Ayuso, 2013 (29) | T | 43 | EGCG | 300 mg daily | Singly-used flavonoids | Flavan-3-ols | Taking capsules | 12 w | 19-49 | 0/43 | 33.7 ± 2.6 | Obese women | HOMA-IR |
| C | 40 | Placebo | A matched placebo | 0/40 | 34.3 ± 3.0 | ||||||||
| Most, 2016 (30) | T | 18 | EGCG and resveratrol | EGCG 282 mg daily and resveratrol 80 mg daily | Mixtures | Flavan-3-ols | Taking capsules | 12 w | 36.1 ± 2.2 | 18/20 | 29.9 ± 0.6 | Overweight and obese subjects | HOMA-IR |
| C | 20 | Placebo | A matched placebo | 38.7 ± 2.2 | 29.5 ± 0.7 | ||||||||
| Rangel-Huerta, 2015 (31) | T | 100 | High polyphenol concentration | A daily dose of 582.5 mg hesperidin, 125 mg narirutin, and 34 mg didymin | Mixtures | Flavanones | Drinking beverage | 31 w | / | / | 33.2 ± 0.5 | Obese and overweight adults | HOMA-IR |
| C | 100 | Normal polyphenol concentration | 237 mg hesperidin, 45 mg narirutin, and 17 mg didymin daily | / | / | 33.1 ± 0.6 | |||||||
| Rondanelli, 2009 (32) | T | 71 | N-oleyl-phosphatidylethanolamine and EGCG | One capsule twice daily, 85 mg N-oleyl-phosphatidylethanolamine and 50 mg EGCG per capsule | Mixtures | Flavan-3-ols | Taking capsules | 2 m | 38.0 ± 10.0 | 18/53 | / | Overweight subjects | HOMA-IR; QUICKI |
| C | 67 | Placebo | A matched placebo | 41.0 ± 11.0 | 14/53 | / | |||||||
| Rondanelli, 2020 (33) | T | 27 | Cynara | 500 mg bid daily. Tablets containing 500 mg of artichoke extract (triple standardized to contain caffeoylquinic acids ≥ 5.0%; flavonoids ≥ 1.5%; cynaropicrin ≥ 1.0%) | Mixtures | Multiple subclasses | Taking capsules | 8 w | 51.4 ± 6.6 | 28/26 | 29.0 ± 3.6 | Overweight and obese with impaired fasting glycemia | HOMA-IR |
| C | 27 | Placebo | A matched placebo | 51.6 ± 6.0 | 29.7 ± 2.5 | ||||||||
| Salden, 2016 (34) | T | 34 | Hesperidin 2S | Two capsules each morning before the consumption of breakfast; each of capsules contained 250 mg hesperidin 2S | Singly-used flavonoids | Flavanones | Taking capsules | 6 w | 54.0 ± 15.0 | 17/17 | 28.2 ± 2.2 | Healthy overweight subjects | QUICKI |
| C | 34 | Placebo | A matched placebo | 53.0 ± 14.0 | 12/22 | 29.7 ± 2.8 | |||||||
| Stendell-Hollis, 2010 (35) | T | 23 | Catechin and EGCG | 960 mL of decaffeinated green tea daily. The green tea bags comprised between 550–700 mg tea solids, providing an average catechin dose of 58.91 mg bag and 32.21 mg EGCG per bag |
Singly-used flavonoids | Flavan-3-ols | Drinking beverage | 6 m | 56.6 ± 8.1 | 0/23 | 31.0 ± 4.3 | Overweight breast cancer survivors | HOMA-IR |
| C | 16 | Placebo | 960 mL daily. The placebo tea was specifically manufactured for use in tea intervention trials of this nature and contained no EGCG | 57.8 ± 8.5 | 0/16 | 28.7 ± 3.8 | |||||||
| West, 2014 (36) | T | 30 | Cocoa/chocolate | 37 g daily of dark chocolate and a sugar-free cocoa beverage (total cocoa = 22 g/d, total flavanols = 814 mg daily) | Mixtures | Flavan-3-ols | Drinking beverage | 10 w | 51.7 ± 1.2 | 15/15 | 27.8 ± 0.6 | Overweight and moderately obese subjects | HOMA-IR |
| C | 30 | Colour-matched controls | A low-flavanol chocolate bar and a cocoa-free beverage with no added sugar (total flavanols = 3 mg daily) | 51.7 ± 1.2 | 15/15 | 27.8 ± 0.6 | |||||||
| Xue, 2016 (37) | T | 29 | Trans-resveratrol-hesperetin co-formulation | One capsule daily contained trans-resveratrol (90 mg) and hesperetin (120 mg) | Mixtures | Flavanones | Taking capsules | 22 w | 45.0 ± 13.0 | 8/21 | 30.0 ± 3.8 | Overweight and obese subjects | HOMA-IR |
| C | 29 | Placebo | One capsule daily with starch in place of bioactives in hard gelatin capsules | 45.0 ± 13.0 | 8/21 | 30.0 ± 3.8 |
M/F, male/female; BMI, body mass index; IR, insulin resistance; T, treatment group; C, control group; d, day; m, month; w, week. EGCG, epigallocatechin-3-gallate; QUICKI, quantitative insulin sensitivity check index; HOMA-IR, homeostasis model assessment of insulin resistance.