Flavonoids: Flavanols, Anthocyanins, Flavanones and Isoflavones Explained
The six flavonoid subclasses explained in plain words, with common food sources and what trials of flavanol, anthocyanin and isoflavone supplements have found.
Content last updated . This page has not been medically reviewed.
Evidence labels used here are explained on Antioxidants Explained.
The six subclasses
| Subclass | Common food sources (Linus Pauling Institute) |
|---|---|
| Anthocyanidins (anthocyanins are the sugar-attached forms) | Red, blue and purple berries, red and purple grapes, red wine. [1] |
| Flavan-3-ols (flavanols), including catechins | Teas (particularly white, green and oolong), cocoa-based products, grapes, berries, apples. [1] |
| Flavonols, including quercetin | Onions, scallions, kale, broccoli, apples, berries, teas. [1] |
| Flavones | Parsley, thyme, celery, hot peppers. [1] |
| Flavanones | Citrus fruit and juices such as oranges, grapefruits and lemons. [1] |
| Isoflavones | Soybeans, soy foods, legumes. [1] |
Food sources are covered on the antioxidant-rich foods and polyphenol-rich foods and drinks pages and in the Functional Foods section, for example citrus fruits, blueberries and soy foods.
What trials of supplements found
Results below are for the specific supplement type, group of people and outcome named. They should not be applied to the food or to other flavonoids.| Subclass | What the source found | Label |
|---|---|---|
| Flavanols (cocoa extract) | The COSMOS trial gave 21,442 US older adults a cocoa extract (500 mg flavanols a day, including 80 mg epicatechin; a study amount, not advice) or placebo. Total cardiovascular events were not significantly reduced, though cardiovascular death was 27% lower, and the authors called for more research. [3] | Mixed |
| Flavanols (green tea) | See green tea and green tea extract and liver safety. | Covered elsewhere |
| Anthocyanins | A meta-analysis of 19 trials found no significant effect on weight, waist size or blood pressure, but an improvement in an insulin-resistance score (HOMA-IR). Fasting glucose and insulin did not change significantly. [4] | Promising but limited (marker only) |
| Flavonols (quercetin) | See quercetin evidence. | Promising but limited |
| Flavanones and flavones | Proper evidence not found. We read no trials of flavanone or flavone supplements this round. | Insufficient evidence |
| Isoflavones (soy) | NCCIH says soy isoflavone supplements or soy protein may help reduce the frequency and severity of menopausal hot flashes, but the effect may be small and results have not been completely consistent. [5] | Promising but limited |
Population studies of flavonoid intake have been inconclusive: some suggest protection from heart disease and cancer, others no effect, and a few possible harm. [2]
Isoflavones need extra care
Isoflavones are compounds similar in structure to the hormone estrogen, according to NCCIH. [5] The Linus Pauling Institute describes them as flavonoids with estrogenic activity. [1] NCCIH says soy use during pregnancy may be unsafe in amounts greater than those found in foods, and that some people are allergic to soy. [5] Because of this estrogen-like structure, people with hormone-related conditions or who take hormone-related medicine should ask a clinician or pharmacist first; see medication interactions.Official intake levels
No recommended intake, adequate intake or upper limit for flavonoids is described in the sources we read.Frequently asked questions
What is the difference between a flavonoid and a polyphenol?
Flavonoids are one class of polyphenols. [1]
Are anthocyanins and flavanols the same thing?
No. They are separate subclasses, found in different foods: berries and red grapes for anthocyanins; tea and cocoa for flavanols. [1]
Does cocoa extract protect the heart?
In COSMOS, it did not significantly reduce total cardiovascular events, though it lowered cardiovascular death, and the researchers said more research is warranted. [3]
Are isoflavones the same as estrogen?
No. NCCIH describes them as similar in structure to estrogen. [5]
Do flavonoid supplements interact with medicines?
They may. The Linus Pauling Institute describes possible interactions, so ask a pharmacist. [1]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety
References
- Linus Pauling Institute, Oregon State University. Flavonoids (reviewed 2016). Read 2026-10-23.
- Ross JA, Kasum CM. Dietary flavonoids: bioavailability, metabolic effects, and safety. Annu Rev Nutr 2002. Read 2026-10-23.
- Cocoa flavanol supplementation and cardiovascular disease events: the COSMOS randomized trial. Am J Clin Nutr 2022. Read 2026-10-23.
- Anthocyanin supplementation and cardio-metabolic biomarkers: systematic review and meta-analysis. Clin Nutr 2019. Read 2026-10-23.
- NCCIH. Soy (updated April 2025). Read 2026-10-23.