Flavonoids are found in a wide range of plant foods, from berries and citrus fruits to tea, dark chocolate, and soybeans. There are six major subclasses of flavonoids, each concentrated in different foods. Knowing which foods belong to which group can help you build a more varied, flavonoid-rich diet.
The Six Subclasses of Flavonoids
Flavonoids are a large family of plant compounds that share a similar chemical backbone but differ enough to split into six main groups: flavonols, flavones, flavanones, flavan-3-ols, anthocyanins, and isoflavones. Each subclass tends to cluster in certain foods, so eating a variety of fruits, vegetables, and plant-based drinks is the simplest way to cover all six.
Flavonols: Onions, Kale, Apples, and Tea
Flavonols are the most widely distributed subclass in the diet. The standout compound is quercetin, and red onions are one of the richest sources at roughly 33 mg per 100 g. Regular yellow onions still deliver about 21 mg per 100 g. Kale comes in at nearly 8 mg per 100 g, and a Red Delicious apple with the peel provides close to 5 mg per 100 g.
Beyond those top sources, you’ll find meaningful amounts of flavonols in lettuce, tomatoes, grapes, berries, broccoli, tea, and red wine. The peel or outer leaves of fruits and vegetables tend to concentrate the most flavonols, so eating apples unpeeled and using the dark outer leaves of lettuce makes a difference.
Flavones: Parsley, Celery, and Peppers
Flavones are less common in the average diet, but a few foods pack them in high concentrations. Fresh parsley is in a league of its own, with apigenin levels that can reach hundreds of milligrams per 100 g depending on the variety and growing conditions. Celery hearts contain about 19 mg of apigenin per 100 g, and Chinese celery is even higher at around 24 mg. Bell peppers contribute smaller amounts, mostly as luteolin, up to about 13 mg per 100 g.
Chamomile tea and fresh mint are also notable sources. Because parsley and celery are often used as garnishes in small amounts, adding a generous handful to salads, soups, or smoothies is a practical way to boost your flavone intake.
Flavanones: Citrus Fruits
Flavanones are almost exclusively a citrus story. Grapefruit is the richest source of naringin, averaging about 17 mg per 100 g of fresh fruit, with white grapefruit slightly edging out pink and red varieties. Lemons lead for hesperidin at roughly 16 mg per 100 g. Oranges, limes, and tangerines round out the group.
The white pith and membranes between citrus segments contain more flavanones than the juice alone. Eating whole citrus segments rather than just drinking the juice gives you a substantially higher dose.
Flavan-3-ols: Tea, Dark Chocolate, and Grapes
Green and black tea are the primary dietary sources of flavan-3-ols (also called catechins). Green tea is particularly rich because the leaves undergo minimal processing, which preserves the compounds.
Dark chocolate is another meaningful source. A 40 g serving of 70% cocoa dark chocolate provides roughly 8 mg of catechin and 29 mg of epicatechin. Higher cocoa percentages don’t always mean more flavonoids; a 70% bar can actually deliver more epicatechin than an 85% or 90% bar, depending on the brand and how the cocoa was processed. Red grapes, red wine, and certain tree fruits like peaches also contribute flavan-3-ols, though in smaller amounts.
Anthocyanins: Berries and Dark-Colored Fruits
Anthocyanins are the pigments responsible for red, purple, and blue colors in fruit, and the darker the fruit, the more it contains. Black raspberries are exceptionally rich, with one cultivar measured at 627 mg per 100 g. Black currants come in at about 411 mg per 100 g. Blueberries are more modest, typically around 119 mg per 100 g for highbush varieties, though this varies with ripeness and cultivar.
Cranberries, blackberries, strawberries, red grapes, and cherries are all solid sources. Even red cabbage, eggplant skin, and purple sweet potatoes contribute anthocyanins. If you see a deep red or purple color in a whole food, anthocyanins are almost certainly present.
Isoflavones: Soy and Legumes
Isoflavones are concentrated almost entirely in soybeans and soy products. Tempeh is the richest common source, with about 36 mg of genistein and 23 mg of daidzein per 100 g. Firm tofu provides roughly 16 mg of genistein and 12 mg of daidzein per 100 g. Regular soy milk is considerably lower, around 6 mg of genistein per 100 g, and reduced-fat versions can dip below 2 mg.
Other legumes like chickpeas and fava beans contain trace amounts, but soy foods dominate this category by a wide margin. Fermented soy products like tempeh and miso may also offer better absorption because fermentation partially breaks down the compounds into forms your body can use more easily.
Why Flavonoids Matter for Health
Flavonoids act as antioxidants by neutralizing reactive oxygen species, unstable molecules that damage cells and contribute to aging and chronic disease. They also reduce inflammation by dialing down key signaling pathways that trigger the body’s inflammatory response. Quercetin, for example, suppresses the production of inflammatory proteins and blocks enzymes involved in pain and swelling. Luteolin works through a similar but distinct route, reducing oxidative stress and calming immune overactivation.
These aren’t marginal effects. Population studies consistently link higher flavonoid intake to lower rates of heart disease, type 2 diabetes, and certain cancers. The benefits appear strongest when people eat a diverse mix of flavonoid-rich foods rather than relying on a single source, which makes sense given that each subclass works through slightly different biological mechanisms.
How Cooking Affects Flavonoid Content
The way you prepare vegetables can dramatically change how many flavonoids end up on your plate. Boiling is the most destructive method because flavonoids leach into the cooking water. In broccoli, boiling retains only about 45% of total flavonoids. Steaming is far gentler, preserving around 88%. Microwaving actually retained the most in one study, with levels near or slightly above 100%, likely because the short cooking time and minimal water prevent leaching.
If you do boil vegetables, using the cooking liquid in soups or sauces recaptures much of what would otherwise be lost. For maximum retention, steaming, microwaving, or eating produce raw are your best options. Stir-frying with a small amount of fat also tends to preserve flavonoids well, and the fat can help your body absorb certain compounds more efficiently.
Building a Flavonoid-Rich Diet
You don’t need exotic ingredients or supplements to get a broad spectrum of flavonoids. A practical daily approach might include a cup of green or black tea (flavan-3-ols), a serving of berries or red grapes (anthocyanins), a citrus fruit (flavanones), onions or leafy greens in a meal (flavonols), and a handful of fresh parsley or celery added to a dish (flavones). If you eat soy products, those cover isoflavones. A few squares of dark chocolate with at least 60% cocoa add another layer of flavan-3-ols.
Color is a useful shortcut. A plate with a variety of reds, purples, greens, yellows, and oranges from whole plant foods will naturally cover most flavonoid subclasses. The compounds are concentrated in skins, peels, and outer leaves, so minimizing peeling and choosing whole fruits over juices preserves the most benefit.