Last updated: September 9, 2021

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Flavonoids are natural compounds essential to our health. Nowadays, their antioxidant properties make them fundamental for the prevention of many common diseases. Flavonoids are found in plants (fruits, vegetables, seeds, soybean) and certain alcoholic (beer, red wine) and non-alcoholic beverages (green tea, black tea).

While the daily flavonoid needs of an adult are relatively small, diets that are poor in plant-based foods won't meet these requirements. This is why flavonoid supplements are valuable to prevent heart disease, atherosclerosis and brain pathologies associated with aging.

Key Facts

  • Flavonoids belong to the class of phytochemicals (or phytonutrients). Needed in small amounts, these nutrients offer protective effects against various diseases.
  • From a health perspective, the antioxidant activity of flavonoids is their most recognized and interesting property. However, they can also act as anti-inflammatories, antimicrobials or anticarcinogens. Each type of flavonoid has specific attributes.
  • Before making your purchase, you should consider a series of key criteria. These include the dosage form, the presence of other added nutrients, the type of flavonoid (quercetin, rutin, anthocyanin), and the concentration of the active ingredient.

Our Selection: The Best Flavonoid Products

Flavonoids are a very heterogeneous group of compounds, with each variety offering different health properties. For this reason, the benefits and indications of any flavonoid product will depend on the specific compound it contains. We've selected some of the best supplements available right now for you:

Shopping Guide: Everything You Should Know About Flavonoids

There are over 5,000 flavonoid compounds in the plant kingdom, hence why we cannot include them all in this article. However, we have selected those that most influence human health and we will tell you about their properties, indications, and recommended consumption.

Mujer con batido

You need to dissolve powdered extracts of green tea, cranberries, and other berries in water or another liquid before consumption.
(Source: Alena Haurylik: 43066860/

What are flavonoids exactly?

Flavonoids are compounds that belong to the class of polyphenols. These small, non-energy (free of calories) molecules have important functions in the human body. These include reducing oxidative damage and inflammation, minimizing the risk of blood clot formation, and strengthening blood vessels.

The metabolism of plants produces flavonoids. This is why they are found in fruits, leafy greens, vegetables, leaves of Camellia sinensis (green and black tea), seeds, and legumes. As we mentioned earlier, we have identified over 5,000 flavonoids; the most studied for their health benefits are the following:

  • Quercetin
  • Kaempferol
  • Rutin (or rutoside)
  • Naringenin
  • Apigenin
  • Silymarin
  • Hesperidin
  • Luteolin
  • Cyanidin
  • Catechin (epigallocatechin gallate)
  • Daidzein
  • Genistein

What are the health properties of flavonoids?

While the antioxidant activity of flavonoids is their most recognized benefit, these phenolic compounds possess various other attributes. Each type of flavonoids has its own chemical structure and food sources, but also different effects on the body. The properties of flavonoids are:

  • Antioxidant: They neutralize compounds called free radicals, responsible for the oxidative damage at the cellular level and, consequently, various diseases (heart disease, atherosclerosis, type II diabetes, cataracts) and an acceleration of aging.
  • Anti-inflammatory: They reduce or inhibit the activity of compounds associated with the inflammatory response. Flavonoids are recommended to complement the treatment of arthritis, inflammatory bowel disease, and sports injuries associated with inflammation.
  • Neuroprotector: They prevent neurodegenerative diseases, especially those related to age, such as Alzheimer's and dementia. Flavonoids also promote learning and improve our cognitive performance.
  • Antithrombotic: They reduce the risk of platelets forming clots that can cause ischemia (cardiac, intestinal, cerebral), myocardial infarction (heart) or thrombosis in the leg veins.
  • Antimicrobial: Certain flavonoids help prevent bacterial infections, while others are useful for alleviating viral conditions.
  • Hepatoprotector: They support the detoxification carried out by the liver and protect it from damages caused by certain toxins and drugs, as well as excessive amounts of alcohol.
  • Anticarcinogen: This is closely related to the antioxidant properties of flavonoids since oxidative stress has been linked to an increased risk of cancer and mutations in the genetic material.
  • Venotonic: They promote blood circulation in veins and capillaries while strengthening the walls of these blood vessels and preventing capillary fragility.
  • Vasodilator: They increase the diameter of blood vessels and decrease blood pressure.


Blueberries are a source of cyanidin and pelargonidin (anthocyanins).
(Source: Corinna Gissemann: 20042389/

Why is the antioxidant activity of flavonoids so important?

Flavonoids are called antioxidants because these molecules are capable of reducing oxidative damage caused by free radicals. Free radicals are generated as a result of the metabolism of nutrients, but certain habits can stimulate their production:

  • Smoking
  • Excessive sun exposure
  • Psychoemotional stress
  • Alcohol abuse
  • Environmental pollution

High levels of free radicals and, therefore, oxidative damage, are related to increased risk of developing very common diseases: type II diabetes, chronic kidney disease, heart disease, atherosclerosis, cataracts, Alzheimer's, and cancer. Antioxidant flavonoids help block free radicals and reduce their harmful effects.

Saul Ruiz Cruz et al.In Flavonoids: From Biosynthesis to Human Health
"Nowadays, flavonoids are major bioactive compounds known for their potential health benefits, which have been used against many chronic diseases such as cancer, antiviral, inflammation, cardiovascular and neurodegenerative disorders; it is widely assumed that active dietary constituents are antioxidant nutrients present in fruits and vegetables."

What types of flavonoids are there?

There are thousands of flavonoids, each with distinct chemical structures and biological functions. For this reason, these compounds have been classified into several groups. From a medical and nutritional perspective, the most important are flavones, isoflavones, flavonols, flavanones, flavanols, and anthocyanidins.

Blueberries are a source of cyanidin and pelargonidin (anthocyanins), while onions provide significant amounts of quercetin (flavonol). Ginkgo biloba provides luteolin (flavone), quercetin, and kaempferol (both flavonols). The following table includes the flavonoid groups and examples of compounds and food sources:

Flavonoid group Example of compounds Food sources
Flavones Apigenin, luteolin Celery, thyme, parsley, mint, green pepper, chamomile, dandelion
Isoflavones Daidzein, genistein, glycitein Soy and soy derivatives: soybean, tofu, tempeh, miso, soy flour, textured soy protein, soy drinks (soy milk)
Flavonols  Quercetin, kaempferol, silymarin, and rutin Onions, apples, milk thistle, Ginkgo biloba, kale, leek, green tea, berries, broccoli, red wine, black grapes
Flavanones Hesperidin (orange), narangenin (grapefruit) Citrus (lemon, lime, orange, grapefruit, mandarin), mint, tomato
Flavanols  Catechins and tannins Green tea, cocoa, apricot, peach, red wine, coffee, grape seeds, berries, pomegranate
Anthocyanins Cyanidin, petunidin, malvidin, pelargonidin Blueberries, blackberries, red cabbage, red onion, purple corn, black grape, red wine, strawberries, raspberries

What types of flavonoid supplements are there?

Flavonoid products tend to come in capsule and tablet form because these compounds often taste bitter or are found in inedible parts of foods. That being said, certain powdered supplements are excellent sources of flavonoids and present very pleasant tastes.

  • Capsules/tablets: They contain various types of flavonoids and may also have added nutrients (vitamin C, vitamin E, calcium). The capsule shell can be made from animal gelatin or modified cellulose (hydroxypropylmethylcellulose). The taste is neutral, and they should be taken during meals with a sip of water.
  • Powder: While you cannot find powder supplements containing 100% flavonoids (for example, pure hesperidin or quercetin), certain dry extracts of fruits and leaves are very high in these phytonutrients. This is the case, for instance, of blueberry, green tea, açai, and Ginkgo biloba. You will need to dissolve this powder in water, milk, or any other liquid before consuming it.

Do vegans need to supplement with flavonoids?

No. In fact, people who follow a vegan or vegetarian diet are often the least in need of flavonoid supplements. As we have discussed earlier, flavonoids are naturally found in plant-based foods and those who follow this type of diet consume a variety of fruits, vegetables, and seeds in large quantities.

Mujer comiendo ensalada y tomando jugo

Produced by the metabolism of plants, flavonoids are found in fruits, vegetables, and leafy greens, among others.
(Source: Kachmar: 76174549/

Are there contraindications for flavonoid supplements?

Since these phytonutrients are naturally present in foods, they only present certain contraindications when used in the form of dietary supplements – capsules (or tablets) or dry extract. The use of flavonoid supplements is contraindicated in the following situations:

  • Pregnancy, breastfeeding, and childhood. Consumption during these stages of life has not been proven to be safe.
  • People with blood coagulation disorders, since flavonoids act as anticoagulants.
  • Hypotensive individuals or with a tendency to hypotension because flavonoids are vasodilators and can decrease tension.
  • Isoflavone supplements (soy and derivatives) are not recommended for diabetic individuals who use insulin. They may interfere with the action of this hormone.

Anyone suffering from a chronic disease or taking medication (permanent or transient) should consult their physician before taking flavonoid supplements so as to prevent side effects. Taken in high dose, flavonoids may interact with antibiotics and their use should be discontinued while taking these drugs.


Daidzein (isoflavone) relieves certain symptoms of menopause (hot flashes and night sweats).
(Source: Monticello: 20483481/

What side effects can flavonoid supplements cause?

Flavonoid supplements are not toxic, but there have been reports of side effects – mainly for the skin and digestive system. Flavonoids can cause rashes, dermatitis, hives, abdominal pain, diarrhea, flatulence, headache, and stomach upset.

Buyer's Guide

You should now be familiar with the various benefits that flavonoid supplements can have on your health. If you already know which type is the most appropriate for your needs, all that's left is for you to evaluate specific criteria to choose the best quality product on the market. In the following section, we will discuss the following factors:

Dosage Form

Capsules and tablets are the most practical way to take flavonoid supplements. They can be easily carried around and all you need is a sip of water to ingest them. On the other hand, you will need to dissolve powdered extracts of green tea, blueberries, and other berries in water or any other liquid before consumption.

Mujer comiendo

Capsules and tablets are the easiest way to take flavonoid supplements.
(Source: Rido: 35534676/

Concentration of the Active Ingredient

As we mentioned earlier, flavonoids offer very healthy properties. However, they can cause damage to the body when taken excessively. While powder extracts rarely provide excessive amounts of flavonoids, certain tablet manufacturers may over-concentrate their products. The ideal portion should provide you with 300 to 600 mg of the active ingredient.

Added Nutrients

As you now know, flavonoid supplements often contain other ingredients (vitamin C and E, bromelain, calcium). These compounds are added to enhance the effects of the flavonoids or to enrich the therapeutic properties of the product you are using. Here are the most beneficial associations of flavonoids and nutrients:

  • Quercetin and bromelain. The latter is an enzyme naturally found in pineapple and is beneficial in improving blood circulation. Quercetin strengthens blood vessel walls.
  • Isoflavones (daidzein, genistein) and calcium. Isoflavones are recommended during menopause to reduce the risk of osteoporosis, while calcium is a mineral that is key for bone health.

Tomate y lechuga

Flavonoids are compounds that belong to the class of polyphenols.
(Source: Subbotina: 21976952/


Individuals suffering from food (peanut, sesame, soy, seafood, milk) or additive (tartrazine) allergies should carefully read the nutrition label for their safety. Gluten and lactose-intolerant people should look for the seals that guarantee that a product is respectively gluten and lactose-free.

Chelsey SchneiderClinical Nutrition Supervisor at Mount Sinai Beth Israel Cancer Center (NY)
"Green tea's potential health benefits derive from catechins, which are powerful antioxidant compounds known as flavonoids."


While they do not provide calories, flavonoids are very interesting phytonutrients from a nutritional point of view due to their antioxidant, venotonic, anti-inflammatory, and hepatoprotective properties. They are commonly found in vegetables, leafy greens, spices, fruits, cocoa, soya, and certain drinks (tea, wine, coffee).

Many people have a diet low in flavonoids because of poor plant food intake or dietary monotony. This is why flavonoid supplements have been created in the form of capsules or powder extracts. When consumed in appropriate doses, they can protect our body from oxidative damage and improve various aspects of our health.

If you found our guide on flavonoids interesting, feel free to leave us a comment in the section below. You can also share this article on your social media!

(Source of featured image: Nitr: 46654564/