Flavonoids or bioflavonoids: what they are, what they are for, where to find them, when to take supplements

Flavonoids or bioflavonoids: what they are, what they are for, where to find them, when to take supplements

Flavonoids are a class of natural molecules that belong to the plant world and have a typical polyphenolic structure.

These substances, present in numerous foods such as fruit, vegetables, tea, cocoa and wine, are associated with a broad spectrum of beneficial effects on health and fall within a wide variety of nutraceutical, pharmaceutical and cosmetic applications.

Specifically, flavonoids have antioxidant, anti-inflammatory, antimutagenic and anticarcinogenic action and for this reason they are widely studied for their beneficial purposes on the human body.

Flavonoids possess several molecular subgroups, which include chalcones, flavones, flavonols and isoflavones, each with its own specific characteristics.

What are Flavonoids?

Flavonoids or bioflavonoids (the term is completely interchangeable) are pigmented molecules that are easily found in the flowers, fruits and leaves of many plant species, including legumes and cereals. There are more than 4,000 types of flavonoids present in nature and united by a chemical structure of the phenolic type or, better, polyphenolic.

Some substances can be found free and not aggregated in phenolic complexes (such as quercitin), or they can be found in the form of dimers and polymers (procyanidins), or even esterified in even more complex structures.

In the same plant, very often, it is possible to find different types of flavonoids, which differ according to the botanical species, the part of the plant that is used and according to the extraction technique.

Small differences in the chemical structure give rise to these subgroups of molecules, identified with the name of flavones, flavonols, flavanones, flavanones, flavanols or catechins, anthocyanins and chalcones.

Inside plants, bioflavonoids perform various functions and, in fact, are responsible for the color and odor essential for pollination, but they also protect plants from biotic and abiotic stresses.

When these substances enter the human body, through food or the intake of pharmaceutical products, they perform completely different activities and beneficial properties.

Properties of bioflavonoids

The studies conducted so far on flavonoids have led to the belief that these molecules are an excellent source of antioxidant and anti-aging power, capable of counteracting the harmful action of free radicals.

Oxidative stress, which affects the human body every day, can overwhelm the antioxidant defenses put in place by cells and tissues, and therefore the integration of foods and products that are rich in flavonoids can be an excellent solution to assist the protection body antioxidant. Furthermore, flavonoids seem capable of:

  • Positively intervene on blood and lymphatic microcirculation, favoring the protection of small venous vessels and reducing stasis and the accumulation of liquids and waste metabolites.
  • Help the liver stay healthy and protect the skin from harmful UV rays.
  • Support the well-being of the immune system.
  • Help in the loss of visceral fat and allow the maintenance of good physical shape.
  • Being involved in the prevention of many multifactorial diseases, such as cardiovascular, inflammatory and above all neoplastic ones.

Although rich in beneficial properties, flavonoids do not have specific claims authorized by EFSA (the European Food Safety Authority) for particular pathologies or therapeutic indications.

Proposals for indications, combined with the benefits described above, were rejected due to the lack of sufficient scientific studies to justify rational use. This does not prevent pharmaceutical companies from producing supplements, nutraceuticals and health products that have flavonoids among the ingredients.

What are flavonoids used for? All benefits

The first thing to remember, as regards indications and benefits, is the fact that the Ministry of Health has not confirmed any of them (following the indications of EFSA), but has included these molecules in the section “Other nutrients and other substances with a nutritional or physiological effect”.

What the Ministry has gone to report are the maximum daily doses for flavonoid complexes and for each flavonoid subcategory.

Specifically, it officially reported that the maximum permissible daily dose relating to the intake of flavonoids as a multi-molecular complex is 1 gram (1000 mg) per day, while as regards individual flavonoids, the maximum permissible daily doses are:

  • Quercetin 200 mg.
  • Quercitrin 300 mg.
  • Rutina 300 mg.
  • Spireoside o spireina 300 mg.
  • Esperidina 600 mg.
  • Hesperitin 300 mg.

The intake of foods rich in polyphenols and/or supplements that contain a mix of flavonoids or a single molecule can bring benefits to the general state of health of the organism.

Particular attention should be paid to their antioxidant capacity, which is the basis of all other beneficial activities for the human body. In fact, by preserving cells and tissues altered and damaged by free radicals and oxidative stress, numerous diseases that afflict the human body today can be prevented.

If you are interested in the topic, discover our in-depth study on quercetin.

Flavonoids: where are they found?

In order to correctly talk about the presence of these molecules within the main food groups, it is necessary to deal with the main subcategories of flavonoids.


It is one of the most abundant and most important flavonoid subgroups. These molecules are present as glucosides in leaves, flowers and fruits.

Celery, parsley, red peppers, chamomile, mint and ginkgo biloba are among the main sources of flavones.

Within this category, it is possible to find molecules such as luteolin, apigenin and mandarinitin, while citrus peels are rich in flavones such as polymethoxylates, tagerin, nobiletin and sinensetin.


Molecules that enter the constitution of other polyphenols, such as proanthocyans.

Flavonols are also abundant in fruits and vegetables (onions, cabbage, lettuce, tomatoes, apples, grapes and berries) and among the most studied are kaempferol, quercetin, myricetin and fisetin.

In addition to classic vegetables, tea and red wine are also important sources of flavonols and have health benefits, which include antioxidant potential and prevention of the risk of cardiovascular disease.


Isoflavonoids are a very large subgroup of flavonoids, but enjoy a limited diffusion in the plant world and are found mainly in soybeans and other legumes.

Isoflavonoids have enormous potential to fight a number of diseases affecting the body, but need further study. Specifically, genistein and daidzein are considered phytoestrogens due to their estrogenic activity in some animal models.


They are the molecules responsible for the colors in plants, flowers and fruits and in fact they accumulate mainly in the external cellular layers of various fruits such as cranberries, black currants, red grapes, raspberries, strawberries, blueberries, blueberries and blackberries.

The stability combined with the potential health benefits of these compounds facilitate their use in the food and pharmaceutical industries.

Foods rich in flavonoids

Below is a table showing the main classes of flavonoids, the food sources in which they are present and the presumed benefits on human health.

FlavonoidsFood sourceHealth benefits
AnthocyaninsCherries, red grapes, red onions and various red berriesAntioxidant action and beneficial effects on the microcirculation
FlavanonesCitrus fruitsAntioxidant and strengthening action for the immune system
Flavonols (among which there is Quercetin)Tea, melee, broccoli, cavaloAntioxidant action and prevention of cardiovascular and metabolic diseases (such as diabetes)
FlavoniChilli, celery and thymeThey have effects on the regulation of estrogen hormones
IsoflavonoidsSoybeans and other legumesAction against some metabolic diseases
ProantocianidineGreen tea, red grapes and wine, blueberries and cocoaMild anti-inflammatory, with beneficial action on blood vessels and urinary tract.

Flavonoid supplements: when to take them and which ones to choose

There are many supplements and nutraceuticals that use flavonoids as active ingredients for the well-being of the organism, or that enrich formulations with specific therapeutic indications.

As already expressed by Aifa and the Ministry of Health, flavonoid-based supplements do not have pharmaceutical indications confirmed by Claims, yet there are many specialties used to assist or prevent various pathologies that can afflict the human body.

The area that concerns the treatment of fragile capillaries presents diosmin-based supplements, such as Venosimine, useful for assisting the treatment of varicose veins and phlebitic complications, and supplements such as Venoruton, very famous for counteracting all diseases caused by increased capillary fragility.

Formulations such as PentavenFast 500 are also used to counteract circulatory disorders and are ideal for leg heaviness and swelling. There are many other supplements that contribute to the well-being of the body, exploiting the antioxidant power of flavonoids such as Quercetin.

Solgar Quercitina Complex, for example, has an antioxidant, supportive and tonic action, but above all it helps to reduce tiredness and fatigue, thanks to its mix of nutrients.

All flavonoid supplements, like most supplements in…