Nutrition · Plant compounds

Flavonoids and Bioflavonoids: Types, Top Foods and Benefits

What flavonoids and bioflavonoids are, the six families and the foods richest in each, how much a day the research points to, what human trials show for your blood vessels, blood sugar, veins and more, and where supplements fit.

By Dr. Josh Axe, DC, DNM, CNS·22-min read

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Evidence-based49 sources citedUpdated October 12, 2026

Published Oct 12, 2026Last updated Oct 12, 2026Editorial policyMedical review policyFact-checking policy

Citrus, dark chocolate, herbs and leafy greens each carry different families of flavonoids.

Flavonoids at a glance

Flavonoids, also called bioflavonoids, are the colorful plant compounds in berries, tea, cacao, citrus, onions and herbs, and the research points to about 500 milligrams a day from food.1 2 They come in six families, and a cup of blueberries or of brewed black tea carries more than 250 milligrams.3 4

Longer life: in Danish adults followed for 23 years, risk of death fell as intake rose to about 500 milligrams a day, then leveled off2
Variety: UK adults who ate the widest range of flavonoids had a 14% lower risk of death than those who ate the narrowest, at the same total amount5
Blood pressure: quercetin at 500 milligrams a day or more lowered systolic pressure by 4.45 mmHg across randomized trials6
Veins: flavonoid preparations lowered the risk of lasting hemorrhoid symptoms by 58% across 14 trials7
Safety: no adverse effects have been tied to high intakes from plant foods, and the few supplement cautions are in the safety section1

Slice a red cabbage and the purple runs across the cutting board. Brew a cup of tea and the water turns amber within a minute. Those colors come largely from flavonoids, the plant compounds that give berries, tea, cacao and red cabbage their deep hues.1 When you eat them, your gut bacteria and your blood vessels put them to work, and the research ties them to healthier arteries, steadier blood sugar and a longer life.8 9 10 2

You'll see them called bioflavonoids on supplement labels and in older books, and the two words name the same family of compounds.1 My approach is food first: color on every plate, a cup of berries most days, green tea, and onions and herbs in your cooking.11 12

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Flavonoids and anthocyanins are plant compounds that give foods their vibrant colors and distinct flavors, like the deep purple of blueberries, the sharp bite of onions, and the rich taste and dark hue of cacao. The rule of thumb is simple: The deeper the color, the stronger the healing potential.Dr. Josh Axe, DC, DNM, CNSFrom Heal Your Cells (2026), p. 172

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Did you know?

In USDA's analysis of the American diet, black tea supplied 88% of the flavan-3-ols people ate, and tea and onions together supplied more than half of the flavonols.13
Your gut bacteria shape what you get from soy. In a study of 1,044 Japanese adults, 44% were equol producers, whose gut bacteria turn daidzein, a soy isoflavone, into equol, a compound that binds estrogen receptors.14
Kale's leading flavonoid is kaempferol, at 46.8 milligrams per 100 grams, about twice its 22.6 milligrams of quercetin.3

What are flavonoids and bioflavonoids?

Quick answer

Flavonoids are a family of more than 5,000 plant compounds within the larger group called polyphenols, and bioflavonoids are the same compounds under an older name.1 They fall into six main families: flavonols, flavones, flavanones, flavan-3-ols, anthocyanidins and isoflavones.1

Plants make flavonoids for their own protection and survival. They help attract pollinating insects, help the plant cope with stresses such as microbial infection, and help regulate its growth.1 In food, flavonols such as quercetin usually come bound to sugars, and these sugar-bound flavonols are the most widely distributed flavonoids in the diet.1

On supplement labels, you'll often see "citrus bioflavonoids," the flavanone-rich extracts made from citrus fruit, covered in the supplement section below.1 Flavonoids are among the many phytonutrients in the foods below.

A short history of "vitamin P"

In 1936, the researchers Stefan Rusznyák and Albert Szent-Györgyi proposed in the journal Nature that plant flavonols be treated as a vitamin, which they called vitamin P.15 The name didn't last: in 1950, four American scientists recommended in Science that the term be discontinued,16 and flavonoids have no Recommended Dietary Allowance and no Daily Value on food labels today.17 Researchers now study them as plant compounds that support health, and the trials below show why they still earn a place on your plate every day.

What are the 6 types of flavonoids?

Scientists sort flavonoids into six families by their chemical structure, and each family favors different foods.1 The last column shows each family's share of what U.S. adults eat.1

Family	Main compounds	Where you find them	Share of U.S. intake
Flavan-3-ols	Catechins such as EGCG; theaflavins and thearubigins; proanthocyanidins	Green, white, oolong and black tea; cocoa; apples; grapes; berries	80%
Flavonols	Quercetin, kaempferol, myricetin, isorhamnetin	Onions, scallions, kale, broccoli, apples, berries, tea	8%
Flavanones	Hesperetin (from hesperidin), naringenin, eriodictyol	Oranges, grapefruit, lemons	6%
Anthocyanidins (anthocyanins)	Cyanidin, delphinidin, malvidin, pelargonidin and others	Red, blue and purple berries; red and purple grapes	5%
Flavones	Apigenin, luteolin	Parsley, thyme, celery, hot peppers	1% or less
Isoflavones	Genistein, daidzein, glycitein	Soybeans, soy foods and other legumes	1% or less

Anthocyanins are anthocyanidins with sugars attached, the form that colors berries and red cabbage.1 Rutin, a popular supplement, is quercetin bound to a sugar, and you may also see it called rutoside.1

Isoflavones have their own USDA database. Among fermented soy foods, natto carries 82.29 milligrams of isoflavones per 100 grams, tempeh 60.61 and miso 41.45.18 Fermented organic soy is the soy to choose, and the hot flash benefit below explains why it matters for women.

Which foods are highest in flavonoids?

Quick answer

Among everyday foods, USDA measurements put elderberries, unsweetened cocoa powder, fresh parsley, red cabbage, blueberries and blackberries near the top per 100 grams, and among the servings in the table below, a cup of brewed black tea or a cup of blueberries carries the most.3 4 Citrus, onions, kale, apples and dark chocolate add different families to the mix.3

Food	Main family	Serving	Flavonoids per serving	Per 100 g
Black tea, brewed	Flavan-3-ols	1 cup (237 g)	About 280 mg	118.4 mg
Blueberries	Anthocyanins	1 cup (148 g)	About 268 mg	180.8 mg
Blackberries	Anthocyanins, flavan-3-ols	1 cup (144 g)	About 213 mg	147.6 mg
Red cabbage, raw	Anthocyanins	1 cup chopped (89 g)	About 187 mg	210.7 mg
Orange	Flavanones	1 fruit (131 g)	About 57 mg	43.5 mg
Strawberries	Anthocyanins	1 cup (144 g)	About 48 mg	33.5 mg
Red onion, raw	Flavonols	½ cup chopped (80 g)	About 45 mg	56.6 mg
Parsley, fresh	Flavones	¼ cup chopped (15 g)	About 35 mg	233.2 mg
Dark chocolate	Flavan-3-ols	1 ounce (28.35 g)	About 31 mg	108.6 mg
Apple, with skin	Flavan-3-ols	1 medium (182 g)	About 28 mg	15.2 mg
Kale, raw	Flavonols	1 cup (21 g)	About 20 mg	93.0 mg
Cocoa powder, unsweetened	Flavan-3-ols	1 tablespoon (5.4 g)	About 15 mg	271.3 mg

Values from the USDA Flavonoid Database, Release 3.3, which measures five flavonoid families (isoflavones and proanthocyanidins have their own USDA databases); totals are the sum of the flavonoids USDA measured. Per-serving amounts are calculated from the per-100-gram values with USDA FoodData Central serving weights: a cup of blueberries weighs 148 grams, blackberries 144 grams, strawberries 144 grams, chopped red cabbage 89 grams and raw kale 21 grams; a cup of chopped fresh parsley weighs 60 grams; an orange 131 grams; a medium apple 182 grams; a cup of brewed tea 237 grams; and a tablespoon of cocoa powder 5.4 grams. Red onion uses USDA's chopped-onion weight of 160 grams a cup.3 4

Flavonoids in 10 everyday foods, per 100 grams

Source: USDA Database for the Flavonoid Content of Selected Foods, Release 3.3 (2018) [3]A longer bar means more flavonoids by weight.

Berries. Their blue, purple and red come from anthocyanins, and the darker berries lead: elderberries, the fruit behind elderberry syrup, carry 518.1 milligrams of flavonoids per 100 grams.3 Cook elderberries before you eat them, as in syrups and jams, because raw or unripe ones can cause nausea and vomiting.19 Choose organic berries when you can, and eat them whole, so their fiber comes along.

Color is a good first clue, and paler foods add other families too: the flavonols in onions, the flavanones in oranges and the flavones in parsley, one more reason to eat a variety.3

Tea. Brewed tea supplies the largest share of flavonoids in the American diet.13 Green tea is made without fermenting the leaves, which keeps its catechins from oxidizing, and EGCG is its key catechin.20 USDA researchers list green tea at 128 milligrams of flavan-3-ols per 100 grams.13 My Anti-Inflammatory Reset calls for two to three cups of green tea a day,11 and matcha, the powdered whole leaf, is the form I like best.21

Onions. Raw red onion carries 39.2 milligrams of quercetin per 100 grams, and USDA lists boiled onions at about the same flavonol level as raw onions, 24.7 against 26.0 milligrams per 100 grams.3 As I said on my show, "Onions are one of your richest common sources of quercetin."22 Onions were on the Israelites' minds in the wilderness, too: "We remember the fish, which we did eat in Egypt freely; the cucumbers, and the melons, and the leeks, and the onions, and the garlick" (Numbers 11:5).

Cacao. Unsweetened cocoa powder carries 271.3 milligrams of flavonoids per 100 grams, nearly all of them flavan-3-ols, and dark chocolate carries 108.6.3 I recommend one to two squares a day of dark chocolate that's 85% cacao or higher, for its cocoa flavanols, which support blood flow and your mitochondria.23

Citrus. Flavanones come mainly from citrus.13 An orange's flavonoids are mostly hesperetin and naringenin, 27.3 and 15.3 milligrams per 100 grams, and lemons and limes carry similar amounts by weight, 53.4 and 46.8.3 Eat the whole fruit rather than the juice, which leaves the fiber behind.

Herbs. As I said on my show, "Gram for gram, dried herbs and spices are the most antioxidant-dense foods on the entire earth."12 Fresh parsley carries 233.2 milligrams of flavonoids per 100 grams, nearly all of it the flavone apigenin, so a quarter cup chopped into a salad adds about 35 milligrams.3 4 Dried parsley is far more concentrated by weight, at 4,854.5 milligrams per 100 grams, though a teaspoon weighs only about half a gram.3 For more, see healing herbs and spices.

How do flavonoids work in your body?

Flavonoids start working in your gut, where bacteria transform them, and the compounds that result reach the lining of your blood vessels, which responds by relaxing.8 24

1They arrive in color

Berries, tea, onions, citrus, cacao and herbs deliver them, each with its own mix of flavonoid families.3

2Your gut bacteria transform them

Gut bacteria break flavonoids into smaller compounds, and those compounds in turn influence which microbes thrive.8 What you get depends partly on your bacteria, as the equol finding above shows.14

3They reach your blood vessels

In lab tests, hesperetin, the form hesperidin takes in the body, switched on nitric oxide production in the cells that line blood vessels; nitric oxide is the signal that lets vessel walls relax.24

4Arteries widen more easily

In people, a cup's worth of blueberries a day and 500 mg of hesperidin both improved flow-mediated dilation, a measure of how well arteries widen. The numbers are in the first benefit below.9 24

5Blood pressure eases

Quercetin supplements and green tea lowered blood pressure across randomized trials, with larger drops at quercetin doses of 500 mg a day or more.6 25

The gut lining may benefit in return. In the MaPLE trial, 66 adults aged 60 and older with signs of a leaky gut lining each tried both an eight-week polyphenol-rich diet, built around foods such as berries, cocoa, green tea and apples, and a control diet, and 51 finished.26 On the polyphenol-rich diet, zonulin, a blood marker of gut leakiness, fell, diastolic blood pressure fell, and fiber-fermenting bacteria that make butyrate became more plentiful.26

How many flavonoids do you need a day?

Quick answer

About 500 milligrams of flavonoids a day: in a 23-year Danish study, the lower risk of death leveled off at about that intake, and an expert guideline recommends 400 to 600 milligrams a day of flavan-3-ols, the family in tea, cocoa, apples and berries.2 27 There's no official daily target, and U.S. adults average 200 to 250 milligrams.17 1

The best guide to how much comes from long-term studies of what people eat. The Danish Diet, Cancer and Health study followed 56,048 adults for 23 years, and 14,083 of them died during that time. Compared with people whose intake was a median 173 milligrams a day, the risk of death was 12% lower at 320 milligrams and 17% lower at 494 milligrams (hazard ratios of 0.88 and 0.83), and it stayed at that level at 726 and 1,201 milligrams.2 Deaths from heart and blood vessel disease and from cancer were lower too, and the link held, though it was smaller, when the researchers also accounted for fish, meat, fiber and fat in the diet.2

Risk of death fell as flavonoid intake rose to about 500 mg a day, then leveled off

Source: Bondonno et al. · Nature Communications, 2019 [2]Lower is better. Each point is the median intake of one fifth of the group, compared with the lowest fifth, after adjusting for smoking, alcohol, body weight, activity, blood pressure, cholesterol, income and other factors.

A pooled analysis of prospective cohort studies points the same way: each extra 100 milligrams of flavonoids a day went with a 6% lower risk of death and a 4% lower risk of dying of heart and blood vessel disease.28 These are population studies, which show links rather than proof, and they line up with the trials later in this guide.

For the flavan-3-ols, an expert panel that reviewed 157 randomized trials and 15 cohort studies issued the first dietary guideline for a bioactive plant compound: 400 to 600 milligrams a day for heart and metabolic health. Its evidence was strongest for systolic blood pressure, cholesterol and blood sugar control, and the panel wrote it as a food-based guideline rather than a recommendation for supplements.27

How many kinds you eat matters too. In a population study of 124,805 UK adults, the people who ate the widest variety of flavonoids, nearly seven more types a day, had a 14% lower risk of death, a 20% lower risk of type 2 diabetes, a 10% lower risk of heart and blood vessel disease and an 8% lower risk of respiratory disease than those with the narrowest variety, with total intake held the same.5 For neurodegenerative disease, the link was with how much people ate: those with the highest intake, a median of about 1,400 milligrams a day, had a 20% lower risk than those who ate the least.5

Eating more kinds of flavonoids went with lower risk across five outcomes

Source: Parmenter et al. · Nature Food, 2025 [5]The most varied fifth compared with the least varied fifth.

Flavonoid-rich diets also go with lower cancer risk. Green tea on its own has given mixed results in a Cochrane review of 142 studies,29 but the Danish cohort had fewer cancer deaths with higher intake2 and the UK adults with the most variety had an 8% lower risk of cancer.5

Here's what about 500 milligrams looks like on a plate:3 4

A cup of blueberries: about 268 milligrams
A cup of chopped red cabbage in a slaw: about 187 milligrams
An orange: about 57 milligrams
Half a cup of chopped red onion: about 45 milligrams

Together that's about 557 milligrams, and a cup of brewed black tea adds about 280 more. In my Anti-Inflammatory Reset, I recommend at least five colors of plants a day, with berries every day,11 which covers the variety finding above as well.

What are flavonoids good for?

Quick answer

Flavonoids' best human evidence is for blood vessels and blood pressure: across randomized trials, quercetin at 500 milligrams a day or more and green tea both lowered blood pressure, and blueberries and hesperidin helped arteries widen.6 25 9 24 Trials and pooled analyses also support benefits for blood sugar, inflammation, hemorrhoids and leg veins, and hot flashes, with promising findings for memory and allergies.30 31 7 32 33 34

Where the research stands

This guide draws on randomized trials, pooled analyses of trials and long-term population studies of flavonoid-rich foods and of single flavonoids taken as supplements. Many trials tested extracts or isolated compounds at doses above what a day of food supplies, so each result names what was studied, and funding by a food or supplement maker is noted where it applies.

Flavonoid benefits, graded by evidence (updated October 2026). Evidence labels are editorial judgments that compare these uses with each other; they aren't formal certainty ratings.
Use	Evidence	What was studied	What the research shows
Blood vessels and blood pressure	Strong	Quercetin, green tea, blueberry powder, hesperidin, cocoa extract	Systolic pressure down 4.45 mmHg on quercetin at 500 mg a day or more; arteries widened more easily6 9 24
Longer life	Moderate	Flavonoids in everyday diets	Risk of death lowest from about 500 mg a day; 6% lower for each extra 100 mg2 28
Blood sugar	Moderate	Anthocyanin extracts and foods; flavonoid-rich diets	Lower fasting blood sugar and HbA1c; 26% lower risk of type 2 diabetes30 10
Inflammation and exercise recovery	Moderate	Quercetin; tart cherry	CRP down 0.33 mg/L on quercetin; faster recovery of strength after hard exercise31 35
Hemorrhoids and leg veins	Moderate	Flavonoid preparations, including rutosides and diosmin	58% lower risk of lasting hemorrhoid symptoms; less leg swelling7 36
Hot flashes	Moderate	Soy isoflavone supplements, a median 54 mg a day	About 21% fewer hot flashes32
Memory and brain aging	Emerging	Flavonol- and flavanol-rich diets; cocoa extract	48% lower risk of Alzheimer's dementia with the most flavonols; memory improved in people who ate few flavanols37 33
Seasonal allergies and colds	Emerging	Quercetin, 200 and 1,000 mg a day	Fewer pollen-allergy symptoms; fewer colds after hard training34 38
Gut lining	Emerging	A polyphenol-rich diet	Zonulin, a marker of gut leakiness, fell26

Flavonoid benefits, ranked by evidence

The benefits below run in order of how strong the human research is. Longer life and the gut lining are covered in the sections above.

Blood vessels and blood pressure

Strong evidenceHuman studyMeta-analyses of 7 and 13 RCTs · RCTs of 24, 115 and 21,442 adults

In a six-month trial of 115 adults with metabolic syndrome, in which neither the people nor the researchers knew who got what, a freeze-dried blueberry powder equal to a cup of blueberries a day improved flow-mediated dilation, how well arteries widen, by 1.45 percentage points and made arteries less stiff; the benefit showed up at a full cup rather than half a cup, and insulin resistance, the trial's main measure, held steady. A blueberry growers' council helped fund it.9 In 24 adults with metabolic syndrome who each tried both, 500 mg of hesperidin a day for three weeks raised flow-mediated dilation to 10.26%, against 7.78% on placebo, and lowered inflammation markers, including hs-CRP.24

Across seven placebo-controlled trials with 587 people, quercetin supplements lowered blood pressure by 3.04/2.63 mmHg, and by 4.45/2.98 mmHg in the trials that used 500 mg a day or more,6 and across 13 randomized trials, green tea and its catechins lowered it by 2.08/1.71 mmHg, with bigger drops in people whose systolic pressure started at 130 or higher.25 In COSMOS, a placebo-controlled trial of 21,442 older U.S. adults, those who took cocoa-extract capsules with 500 mg of flavanols a day for a median 3.6 years had 27% fewer deaths from heart and blood vessel disease, a secondary measure; total cardiovascular events, the trial's main measure, weren't significantly lower, and a chocolate maker's nutrition arm funded the trial and donated the capsules.39 Among 93,600 young and middle-aged women followed for 18 years, those who ate the most anthocyanins had a 32% lower risk of heart attack.40 For the full plan, see natural ways to lower blood pressure.

Study takeaway: blueberries, hesperidin, quercetin and green tea helped arteries widen or lowered blood pressure in randomized trials.

Blood sugar and type 2 diabetes

Moderate evidenceHuman studyMeta-analysis of 32 RCTs · cohort of 113,097 adults

Across 32 randomized trials with 1,491 people, anthocyanins from berry extracts and foods lowered fasting blood sugar, after-meal blood sugar and HbA1c, along with total and LDL cholesterol; results varied from trial to trial and held up when the trials at higher risk of bias were set aside.30 In 113,097 UK adults followed for 12 years, those whose diets were richest in flavonoid foods, about six servings a day, had a 26% lower risk of type 2 diabetes, and tea, berries and apples were each linked with lower risk, by 21%, 15% and 12%.10

Study takeaway: anthocyanins lowered blood sugar and HbA1c across 32 trials, and flavonoid-rich diets went with 26% lower diabetes risk.

Inflammation and exercise recovery

Moderate evidenceHuman studyMeta-analyses of 7 RCTs and 14 studies · RCT of 10 adults

Across seven randomized trials, quercetin supplements lowered C-reactive protein (CRP), the main blood marker of inflammation, by 0.33 mg/L.31 Tart cherries, rich in anthocyanins, show the same pattern. In a placebo-controlled trial of 10 healthy adults who each tried both, 500 mg of tart cherry extract a day for four weeks lowered CRP by 23.0% and uric acid by 37.4%; three of the authors work in the supplement-ingredient industry.41 I've pointed to this trial on my show.12 After hard exercise, tart cherry products helped muscle strength recover and eased soreness across 14 studies.35

In our house, tart cherries are for athletic recovery. My daughter, who started swimming, snacks on unsweetened tart cherries, and when I work out, I add tart cherry juice to a shake of protein powder and creatine; it's the only time I drink fruit juice.12 For more, see anti-inflammatory foods.

Study takeaway: quercetin lowered CRP across seven trials, and tart cherry helped strength recover after hard exercise.

Three markers for your inflammation and blood sugar picture

These markers give you a baseline to track as berries, tea, onions and herbs become a bigger part of your day. They show how your body is doing overall; they can't single out what flavonoids are doing. Go over your numbers with your practitioner.

hs-CRP: Low-grade inflammation anywhere in the body, the marker quercetin and tart cherry lowered in trials.
HbA1c: Your average blood sugar over about three months, which anthocyanins lowered across 32 trials.
Fasting glucose: Your blood sugar first thing in the morning.

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Hemorrhoids and leg veins

Moderate evidenceHuman studyMeta-analysis of 14 RCTs · Cochrane review of 56 RCTs

Across 14 randomized trials with 1,514 people with hemorrhoids, flavonoid preparations lowered the risk of lasting symptoms by 58% and reduced bleeding, pain, itching and recurrence, though the authors noted uneven trial quality.7 For leg veins, a Cochrane review of 56 placebo-controlled trials of oral vein remedies, 39 of them testing rutosides or diosmin-type flavonoids, found they probably ease leg swelling slightly, with about a 30% lower risk of swelling than on placebo, and trim ankle circumference by 4.27 mm, with little change in quality of life.36 See how to get rid of hemorrhoids and varicose veins for the rest of the plan.

Study takeaway: flavonoid preparations lowered the risk of lasting hemorrhoid symptoms by 58% and eased leg swelling.

Hot flashes

Moderate evidenceHuman studyMeta-analyses of 13 and 9 RCTs · women around and after menopause

Across 13 placebo-controlled trials, soy isoflavone supplements, extracted from soybeans or made in a lab, a median 54 mg a day for six weeks to a year, made hot flashes about 21% less frequent than placebo, and across 9 trials, 26.2% less severe.32 For food, fermented organic soy is the form I recommend. As I said on my show, "I like natto, tempeh and miso, where it's fermented organic soy. Especially for women who are postmenopausal, I think that is amazing for their health."42 The isoflavone amounts in each are in the six types section above, and menopause relief covers more natural steps.

Study takeaway: soy isoflavones made hot flashes about 21% less frequent across 13 trials.

Memory and brain aging

Emerging evidenceHuman studyCohorts of 921 and 77,335 adults · RCT of 3,562 older adults

In a population study of 921 older adults in the Chicago area, those who ate the most flavonols had a 48% lower risk of Alzheimer's dementia than those who ate the least.37 In two long-running U.S. studies of 49,493 women and 27,842 men, those with the highest flavonoid intake had 19% lower odds of a 3-point rise on a scale of memory and thinking complaints they reported themselves.43 In COSMOS-Web, 3,562 older adults took cocoa extract with 500 mg of flavanols a day or a placebo for three years. Memory improved in the people whose diets were lowest in flavanols or poorest in quality, though not across the whole group; two of the authors work for, and two were funded by, the company that supplied the extract.33 As I've written, "For anyone concerned with maintaining mental sharpness and resilience with age, berries are daily brain food."21 See brain foods for more.

Study takeaway: people who ate the most flavonols had 48% lower risk of Alzheimer's dementia, and flavanols improved memory in people who ate few.

Seasonal allergies and colds

Emerging evidenceHuman studyRCTs of 66 and 40 adults

In a trial of 66 Japanese adults with pollen allergies, in which neither the people nor the researchers knew who got what, 200 mg a day of a lecithin-bound quercetin for four weeks eased sneezing and improved sleep and daily-life scores against placebo in the 60 who were analyzed, and eye itching eased in the first week; the ingredient's maker paid for the trial.34 In 40 trained male cyclists, 1,000 mg of quercetin a day, taken for three weeks before, during and for two weeks after three days of hard riding, cut colds in those two weeks to 1 of 20, against 9 of 20 on placebo, though the immune measures the researchers tracked didn't change.38 For more food-first steps, see natural allergy relief.

Study takeaway: quercetin eased pollen-allergy symptoms in one trial and cut colds after hard training in another.

Flavonoid and bioflavonoid supplements: what to know

Quick answer

Start with food, and use a flavonoid supplement for a specific goal: in randomized trials, quercetin at 500 milligrams a day or more lowered blood pressure and C-reactive protein.6 31 Flavonoid preparations such as rutosides and diosmin have their best record for hemorrhoids and leg swelling.7 36

Food comes first. A cup of berries brings fiber and hundreds of other compounds along with its flavonoids, and your gut bacteria do much of the work of transforming them. As I said on my show, "You cannot supplement your way out of an inflammatory diet, but you can eat your way out of one."12 I put whole foods first as often as possible, and I'm also in favor of smart supplementation when targeted support is needed.21

When a supplement makes sense, here's how the main options line up:

A whole-food powder for general support: As I said on my show, "If you want to take a longevity superfood supplement, don't just take the extract, take the entire food."44 A powder made from whole berries brings the full food.
Quercetin: The quercetin dose in my Anti-Inflammatory Reset is 500 mg a day,11 the amount at which trials saw blood pressure and CRP fall.6 31
Green tea extract: On my show, I've called green tea extract another amazing longevity supplement.44 Read its liver-safety note in the safety section before you start.
Fisetin with quercetin: In my Mitochondrial Longevity Protocol, the two are taken together as a monthly pulse, an approach drawn from research on aging, worn-out senescent cells.23
Citrus bioflavonoids, rutosides or diosmin: These have their best human record for hemorrhoids and leg swelling, covered in the benefits above.7 36

What are citrus bioflavonoids?

Citrus bioflavonoid supplements carry the flavanones of citrus fruit, mainly hesperidin, naringin and eriocitrin, and some add quercetin, rutin or the flavones from citrus peel.1 Hesperidin-complex supplements are sold in daily doses of 500 mg to 2 grams.1 At 500 mg a day, hesperidin improved how well arteries widen in the trial described in the first benefit above.24 For whole-food sources, see the citrus foods above.

Is vitamin C with bioflavonoids better?

A single dose of vitamin C may be absorbed better. In a study of eight fasting adults, a single 500 mg dose of vitamin C in a citrus extract with bioflavonoids was absorbed 35% better than plain vitamin C, though more slowly.45 With regular daily use, a review of human studies found no difference between food-derived and synthetic vitamin C,46 so the bioflavonoids earn their place through their own benefits.

Which forms absorb best?

The form a flavonoid comes in changes how much reaches your blood. A review of 31 human studies found that quercetin bound to a chain of glucose molecules was absorbed about 20 times better than plain quercetin, the form sold in many supplements, and quercetin wrapped in lecithin also absorbed about 20 times better.47 1 Taking quercetin with a meal that contains fat and fiber roughly doubled absorption.47 Food delivers quercetin already bound to sugars, together with the fat and fiber of a real meal.1

Want help adding more flavonoids to your day?

Ask Dr. Axe AI. Answers are grounded in this library, with sources shown.

Are flavonoids safe? Side effects and interactions

Quick answer

Flavonoids from food are safe: no adverse effects have been tied to high intakes from plant foods.1 With supplements, keep green tea extract well below 800 milligrams of EGCG a day and take it with food, review quercetin with your prescriber if you take a blood thinner, and skip high-dose flavonoid supplements during pregnancy and breastfeeding.20 48 1

Your body absorbs relatively little of most flavonoids and clears them quickly, which may explain why food amounts cause no problems.1 Supplements deliver far more at once, so a few situations call for care. Interaction check: moderate for flavonoid supplements, mainly with blood thinners, and low for flavonoid foods.48 1

Before you take a flavonoid supplement

Quercetin at supplement doses: In clinical studies, quercetin glycosides at 3 to 1,000 mg a day for up to three months caused no significant side effects.1
Green tea extract: In trials, extracts supplying 800 mg or more of EGCG a day raised liver enzymes, and Europe's food safety authority couldn't identify a lower extract dose it could call safe, while green tea brewed the traditional way is generally considered safe.20 If you take an extract, stay well below that line and take it with a meal, since an empty stomach raises how much EGCG reaches your blood,20 and stop and get checked if you notice yellowing skin or eyes or dark urine.
Warfarin and other blood thinners: In one documented case, a 79-year-old man on warfarin, who also took the heart-rhythm drug amiodarone, started a supplement with 250 mg of quercetin and 500 mg of vitamin C, and his INR, the clotting test, rose from 2.5 to 7.5 within days; it was back to 2.5 five days after he stopped.48 High supplement intakes could, in theory, raise bleeding risk with blood thinners and antiplatelet drugs.1 If you take one, review any flavonoid supplement with your prescriber before starting, and don't change the prescription on your own.
Pregnancy and breastfeeding: The safety of flavonoid supplements in pregnancy and while nursing hasn't been established.1 Enjoy flavonoid foods freely, and save high-dose flavonoid supplements for after you've weaned.
Grapefruit and medications: Grapefruit's best-known drug interactions come from compounds called furanocoumarins.49 If a prescription label warns about grapefruit, follow it for grapefruit and its juice.
Vein remedies: In the Cochrane review, people taking vein remedies reported slightly more side effects than on placebo, mostly stomach upset.36

The bottom line

Are flavonoids good for you?

Yes. Flavonoids are the colorful compounds that make berries, tea, cacao, citrus, onions and herbs some of the most valuable foods you can eat, and the research ties them to healthier blood vessels, steadier blood sugar, calmer inflammation and a longer life. People have prized these foods for thousands of years, and I take that long record seriously. The blood vessel and blood pressure evidence is the strongest, and the memory and allergy findings are promising.

Aim for about 500 milligrams a day from as many kinds of colorful plants as you can: a cup of berries most days, green tea, onions and herbs in your cooking, citrus, and a square or two of dark chocolate. Use supplements for a specific goal, and read the safety section before you start one. Your body knows how to heal, and every colorful meal gives it more to work with.

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Flavonoids: frequently asked questions

What are flavonoids?

Flavonoids are a family of more than 5,000 plant compounds, part of the larger group called polyphenols, that give many fruits, vegetables, teas and herbs their color.1 21 They come in six main families: flavonols, flavones, flavanones, flavan-3-ols, anthocyanidins and isoflavones.1

What are bioflavonoids?

Bioflavonoids are flavonoids under an older name, which you'll still see on supplement labels, as in citrus bioflavonoids.1 In the 1930s, researchers proposed calling them vitamin P, a term dropped in 1950.15 16

Are flavonoids the same as polyphenols?

Flavonoids are one family within the larger group of plant compounds called polyphenols.1 Every flavonoid is a polyphenol, though not every polyphenol is a flavonoid.

What foods are highest in flavonoids?

Elderberries, unsweetened cocoa powder, fresh parsley, red cabbage, blueberries and blackberries are among the richest everyday foods per 100 grams, by USDA data.3 By the serving, a cup of brewed black tea carries about 280 milligrams and a cup of blueberries about 268.3 4

How many flavonoids do you need a day?

About 500 milligrams a day from food is a good target: in a 23-year study of 56,048 Danish adults, the lower risk of death leveled off at about that intake.2 There's no official daily requirement, and U.S. adults average 200 to 250 milligrams.17 1

What are citrus bioflavonoids?

Citrus bioflavonoids are the flavonoids of citrus fruit, mainly hesperidin, naringin and eriocitrin, sold as supplements that sometimes add quercetin, rutin or citrus-peel flavones.1 In a trial of 24 adults with metabolic syndrome, 500 mg of hesperidin a day for three weeks improved how well arteries widen.24

Is vitamin C with bioflavonoids better?

A single dose can be absorbed better: in eight fasting adults, a single 500 mg dose of vitamin C in a citrus extract with bioflavonoids was absorbed 35% better than plain vitamin C, though more slowly.45 With regular daily use, a review found food-derived and synthetic vitamin C were absorbed equally well.46

Do flavonoids lower blood pressure?

Yes, modestly. In placebo-controlled trials, quercetin at 500 mg a day or more lowered blood pressure by 4.45/2.98 mmHg, and across 13 randomized trials, green tea and its catechins lowered it by 2.08/1.71 mmHg.6 25

Are flavonoids anti-inflammatory?

Yes. Across seven randomized trials, quercetin lowered C-reactive protein, the main blood marker of inflammation, by 0.33 mg/L, and in a 10-person trial in which each person tried both, tart cherry extract lowered it by 23%.31 41

Does dark chocolate have flavonoids?

Yes. Dark chocolate carries 108.6 milligrams of flavonoids per 100 grams, about 31 milligrams an ounce, and unsweetened cocoa powder carries 271.3 per 100 grams.3 4 Dr. Axe recommends one to two squares a day of 85% or darker chocolate.23

Does green tea have flavonoids?

Yes. USDA researchers list green tea at 128 milligrams of flavan-3-ols per 100 grams, and its key catechin is EGCG.13 20 Dr. Axe's Anti-Inflammatory Reset calls for two to three cups of green tea a day.11

Does coffee have flavonoids?

Very few: USDA lists brewed coffee at 0.18 milligrams of flavonoids per 100 grams.3 Dr. Axe's Anti-Inflammatory Reset still counts coffee as rich in polyphenols, the larger family flavonoids belong to, at one or two cups a day without sugar.11 1

Is soy a good source of flavonoids?

Fermented organic soy is a good source of isoflavones: natto carries 82.29 milligrams per 100 grams, tempeh 60.61 and miso 41.45.18 Across 13 placebo-controlled trials, soy isoflavone supplements made hot flashes about 21% less frequent.32

Can flavonoids help with allergies?

They may. In a trial of 66 adults with pollen allergies, 200 mg a day of a lecithin-bound quercetin for four weeks eased sneezing and improved sleep and daily-life scores against placebo.34

Are flavonoid supplements safe?

Generally, yes: in clinical studies, quercetin glycosides at up to 1,000 mg a day for up to three months caused no significant side effects.1 Keep green tea extract well below 800 mg of EGCG a day and take it with food, review supplements with your prescriber if you take a blood thinner, and skip them during pregnancy.20 48 1

Do flavonoids help you live longer?

They're linked with a longer life: each extra 100 milligrams a day went with a 6% lower risk of death in a pooled analysis of cohort studies, and the widest variety went with a 14% lower risk in UK adults.28 5

Freshness & method note

October 12, 2026 — Rewrote the page in full under Dr. Axe's byline. Added the six flavonoid families with their foods and share of U.S. intake; USDA Flavonoid Database Release 3.3 values per 100 grams and per serving, and USDA isoflavone values for natto, tempeh and miso; how much a day the research supports, from the Danish cohort's plateau near 500 milligrams, the 400 to 600 milligram flavan-3-ol guideline and the UK Biobank variety finding; human trials with their numbers for blood vessels and blood pressure, blood sugar, inflammation and exercise recovery, hemorrhoids and leg veins, hot flashes, memory, and allergies and colds; how flavonoids work in the body; the "vitamin P" history; supplement forms and absorption; three charts; and an FAQ. Replaced the claim that bioflavonoids keep vitamin C from breaking down with the absorption studies, and the general risks list with specific guidance on green tea extract, warfarin, pregnancy and grapefruit. Corrected the statement that bioflavonoids are best absorbed from raw foods. Removed the catechin dose for hepatitis, the cold sore and purpura claims, the comparison of quercetin with allergy medications, and red wine as a flavonoid source.

Originally published January 31, 2024. —

References

Dr. Josh Axe, DC, DNM, CNS

Doctor of Natural Medicine · Founder, DrAxe.com

Dr. Axe is a certified doctor of natural medicine, clinical nutritionist, and multiple New York Times bestselling author. He has spent 20+ years in clinical practice helping people heal at the root cause and founded one of the most-visited natural-health platforms in the world.

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