Table 1.
Select human studies of flavonoids and colorectal cancer.
| Type of Food/Flavonoid | Subjects | Type of Study | No. of Subjects | Dose | Length of Study | Outcome | Reference |
|---|---|---|---|---|---|---|---|
| Anthocyanidin-rich bilberry extract | Ulcerative colitis | Intervention | 13 | 10 mg/mL | 6 weeks; 9 weeks follow-up | Reduced NF-κB activation and production of pro-inflammatory mediators in colon biopsies | [137,138] |
| Anthocyanidin-rich bilberry extract | Colorectal cancer | Intervention | 25 | 0.5–2.0 g | 7 days | Reduced cellular proliferation in tumors | [139] |
| Black raspberry powder | Colorectal cancer | Intervention | 20 | 60 g | 1–9 weeks | Decreased methylation of various tumor suppressor gene promoters, increased apoptosis, and decreased surrogate markers of cellular proliferation in colorectal cancer and normal adjacent tissue biopsies | [140] |
| Apigenin/(-)-epigallocatechin gallate (EGCG) | Polypectomy and resected CRC patients | 2-arm intervention | 87 | 20 mg apigenin, 20 mg EGCG | 304 years | Decreased recurrence rate of neoplasia (adenoma or CRC) | [141] |
| Quercetin | Healthy versus CRC patients | Case–control | 2664 | Quercetin intake estimated based on food frequency questionnaires | Inverse association between proximal, but not distal colon cancer risk and quercetin intake | [186] | |
| Flavonoids/quercetin, myricetin, kaempferol | Healthy | Observational | 71,976 women, 35,425 men | Total flavonoid and individual flavonol intake based on food frequency questionnaire | No association between flavonoid intake CRC risk | [185] | |
| Flavonols | History of adenomatous polyp | Randomized intervention trial | 1905 | Low-fat, high fiber, high vegetable and fruit intake vs. no intervention control questionnaire | 4 years | High intake of flavonols was associated with significantly decreased risk of advanced adenoma recurrence | [142] |
| EGCG | Polypectomy patients | Randomized intervention trial | 136 | 1.5 g green tea extract tablets (52.5 mg EGCG) | 1 years | Reduced incidence of adenoma recurrence | [192] |
| Green tea | Healthy | Intervention | 400 mL green tea liquid | 2 weeks | Alterations in the gut microbiome, including increased short-chain fatty acid-producing bacteria and decreased pro-inflammatory bacteria | [207] | |
| Flavonoid | Healthy | Observational | 477,312 | Flavonoid intake based on food frequency questionnaires | Mean follow-up 11 years | No association between total flavonoid intake and risk of CRC or any CRC subtype | [209] |
NF-κB: nuclear factor kappa light chain enhancer of activated B cells; CRC: Colorectal cancer.