Complete Guide to Flavonoids: Expert Insights and Practical Solutions

Written by Salma Younas | Last updated on August 4, 2023

Flavonoids are organic substances that possess many medicinal benefits and boost your body’s health. 

Flavonoids are now acknowledged as crucial components in a variety of nutraceutical, pharmaceutical, medical and cosmetic applications.

Flavonoids are used for vegetable growth and defense against dental plaque. Flavonoids are also ample in plant-based foods and beverages such as fruits, vegetables, tea, cocoa, and wine. They are therefore called dietary flavonoids. 

They are known for their antioxidant properties and help protect cells from free radical damage. 

Anti-inflammatory, anti-cancer, and antiviral effects have also been attributed to flavonoids. They may help reduce the risk of stroke and 

other cardiovascular diseases.

This article will cover the vast topic of flavonoids from all aspects in the best way possible. It will include its description, benefits, and side effects on one’s body in detail.

What are Flavonoids?

flavonoids food


Flavonoids also known as bioflavonoids are polyphenolic secondary metabolites found in natural food resources. 

Types of Flavonoids

There are hundreds of types of flavonoids, approximately 600. However, six types are the most important ones which are classified on the basis of their chemical structures. 

  1. Flavonols: Onions, leeks, Brussels sprouts, kale, broccoli, tea, berries, beans and apples are food sources rich in flavonoids. It has anti-inflammatory and antioxidant properties that diminish the risk of chronic and cardiac. 
  2. Flavan-3-ols: Food sources rich with this type are white tea, green tea, black tea, apples and grapes. . Flavanols work well in diminishing chronic fatigue syndrome and improve neurological health.
  3. Flavones: These play an important role in maintaining our body’s cholesterol and weight. They also play an important role in the prevention of prostate cancer. 
  4. Anthocyanins: These play the role of antioxidants in the body. They are mainly found in berries, pomegranates, and grapes. Anthocyanins decrease the risk for lung cancer. 

Chemical structure of flavonoids

flavonoids chemical structure

Chemically, flavonoids have the structure of a 15-carbon skeleton, which consists of two phenyl rings (A and B) and a heterocyclic ring (C, the ring containing the embedded oxygen).

The functional hydroxyl groups in flavonoids can donate electrons through resonance to stabilize free radicals. 

Sources of flavonoids 

food source of flavonoids

Flavonoids are compounds found in natural substances like vegetables and fruits. Many plants also contain dietary bioflavonoids. They are widely responsible for the pigmentation and coloration of plants. 

A variety of flavonoids are found in citrus fruits. Foods like cocoa, berries, parsley, bananas, wine, and green tea are rich sources of flavonoids. 

Tea and onions have the highest content of flavonoids i.e. about over one-half of the intake. Orange juice, wine, canned kale, kaempferol, and soybean oil are major sources of flavonoids. 

Despite the great intake of all the organic sources of flavonoids, their availability to one’s body is generally low. They are rapidly and extensively metabolized and excreted from the body which gives it less time to be absorbed by the target tissues. 

Also, the bioavailability of each type of flavonoid differs based on its chemical structure. Isoflavones are the most bioavailable while anthocyanins and catechins are readily absorbed in the body.

Factors affecting flavonoids content 

Environmental conditions and many other factors affect the growth of plants - plants containing flavonoids in this case.


The amount of sunlight, water, and soil nutrients can affect the flavonoid content of a plant.


Ripeness affects flavonoid content in a variety of ways. As fruits and vegetables ripen, their flavonoid content increases. This is because ripening increases the production of enzymes that break down cell walls, allowing the flavonoids to be released. 

Additionally, the sugar content of fruits and vegetables increases as they ripen, which can also increase the flavonoid content. 

However, over-ripening can lead to a decrease in flavonoid content, as the enzymes that break down cell walls can also break down the flavonoids.

Processing and cooking 

Processing methods such as drying, roasting, and brewing can affect the flavonoid content of a plant. Boiling and steaming can cause loss of flavonoids whereas baking can increase the content.

Hence, it can be concluded that the longer the food is cooked, the more the flavonoid content is lost.

Plant variety

Different varieties of plants contain different levels of flavonoids. For instance, parsley contains a larger amount of flavonoids than any other American food.

Soil conditions

Soil diversity can influence flavonoid levels in plants in different ways. Different soil types provide different amounts of nutrients, which can affect the amount of flavonoids produced by plants. 

Soils with high levels of nitrogen, phosphorus, and potassium have higher levels of flavonoids in plants. In addition, soil pH can also affect flavonoid levels, as acidic soils tend to produce higher levels of flavonoids than neutral or alkaline soils. 

Plants grown in dry soil tend to produce higher levels of flavonoids than plants grown in moist soil

Health benefits of flavonoids

Anti-inflammatory properties 

It has been proved that flavonoids have properties that reduce inflammation.

This is done by modulating the activity of specific enzymes involved in inflammation which are cyclooxygenase-2, and lipoxygenase, production of proinflammatory cytokines, and by oxidative stress reduction.

Antioxidant properties

Flavonoids have the ability to reduce oxidative stress on our bodies. 

Now what is oxidative stress? It is a state in which there is an excess of unstable molecules called free radicals. These free radicals produced during metabolic processes can damage body cells, DNA, and protein and enhance tissue damage. 

Flavonoids reduce this oxidative stress by scavenging these free radicals and diminishing reactive oxygen species that cause oxidative damage.

Cardiovascular Health

Flavonoids reduce the risk of heart disease, and atherosclerosis by preventing plaque buildup, stroke, and other cardiovascular diseases and improve vascular function.

Flavonoids improve circulation by increasing the production of nitric oxide, which helps relax and dilate blood vessels. They also help reduce the risk of blood clots that can cause heart attacks and strokes.

Cancer Prevention 

It has been discovered that flavonoids inhibit the growth of cancer cells. Plus, it also reduces the adverse effects of chemotherapeutic agents and radiotherapy.

Brain Health

Flavonoids protect brain cells from damage. They help improve cognitive function and memory.

Anti-diabetic effect

Flavonoids improve the pathogenesis of diabetes and regulate carbohydrate digestion. It also reduces the risk of type 2 diabetes by improving insulin sensitivity and reducing inflammation.

Neuroprotective properties   

Flavonoids prove to have potential neuroprotective effects. It reduces the risk of neurodegenerative diseases like Alzheimer's and Parkinson's improves cognitive function, and protects neurons from damage by oxidative stress.

Anti-aging effects

Flavonoids can delay aging and enable a healthy lifespan. It helps reduce oxidative damage which has an anti-aging effect on one's body. 

It improves skin elasticity, protects skin from UV damage, and lightens skin tone. It also reduces age-related diseases like cancer, cardiovascular problems, and brain cognition disorders.

Flavonoids and skin health 

Flavonoids can do wonders on the skin if the intake and dosage are appropriate. 

It delays the aging process and enables a healthy lifespan and maintains metabolic homeostasis. 

Senescence is a process by which the cell ages and these flavonoids play a role in slowing this down by inhibiting senescent cells. 

It tightens skin, reduces wrinkles, lightens skin tone, and protects against aging. It minimizes UV-induced oxidative damage and boosts photoprotection.  

It reduces inflammation and serves as a great antioxidizing agent for the skin. Skin care products that contain flavonoids greatly improve skin quality and appearance. It can provide protection against skin cancer.

Potential side effects of flavonoids

Flavonoids are generally considered safe but can cause some side effects when taken in high doses. 

These side effects include stomach ache, headache, allergic reactions, interaction with certain drugs, increased risk of bleeding, Low blood pressure, diarrhea, skin rash, Malaise, and Insomnia.

Drug interaction with flavonoids

The high risk of herbal medicine-drug interactions caused by flavonoid-rich herbal medicines and dietary supplements is becoming very common in our daily life.

The presence of nutrients in food affects the bioavailability of co-ingested flavonoids. The binding affinities and possible (non)covalent interactions of flavonoids with food proteins, carbohydrates, and fats are directly related to the physicochemical properties of flavonoids. 

Proteins in milk reduce the absorption of polyphenols from cocoa and tea. The presence of flavonoid-bound milk proteins has been shown to attenuate the antioxidant capacity of flavonoids in vitro. 

Some carbohydrate-rich foods may increase flavonoid deglycosylation and absorption by stimulating gastrointestinal motility and mucosal blood flow. Dietary flavonoids have been shown to interfere with carbohydrate digestion and absorption. 

Flavonoids dosage and safety guideline

Flavonoids are generally considered safe to consume. The recommended daily intake of flavonoids has not been established, but the average intake of flavonoids in the United States is estimated at 20-50 milligrams per day.

It’s important to keep in mind that flavonoids can interact with certain medications and herbs. Therefore, it is important to consult your doctor before taking dietary supplements containing flavonoids. 

Flavonoids can also be the cause of allergic reactions in some people. Therefore, one should be aware of the possible side effects.

Hence, it’s better to get flavonoids through your diet instead of supplements. One should not take flavonoids without a physician’s prescription. When taking flavonoid supplements, it is important to follow label directions and not exceed recommended dosages.

Future research on flavonoids

Area of interest

There is an increased interest in flavonoids from plant sources as they are involved in various health benefits. 

The area of interest in future research on flavonoids is based on the isolation, identification, characterization, and function of flavonoids. Their future research is based on their application of health benefits. 

Furthermore, the research is based on a prediction of flavonoids as a potential drug in the prevention of chronic diseases, cancer, stroke, and coronary heart diseases. 

The future model of flavonoids includes the processing effect, dietary and bioavailable dose, absorption, metabolism, and the relationship between flavonoids and subclasses. 

The future of flavonoids requires a multi-disciplinary approach that should involve human intervention, epidemiology, and cellular study.

Limitation of current research

The following are considered limitations in flavonoids research

  • It Is a low yield product as we get from plants the average amount we can have is in milligrams .
  • Extraction of flavonoids material is somehow an expensive procedure and requires numerous steps by the individual to perform.
  • Another limitation of flavonoids extraction is that they are extremely liable, so there is a high chance of their degradation and change of their chemical composition which can lead to loss of their action and function.
  • They need a significant amount of time for their therapeutic effect to be visible to the person who is using it.
  • Flavonoids research has a high study cost which may make it questionable to put work on.
  • Low solubility and stability are other concerns for flavonoids.
  • They may show their interaction with other chemical drugs in the body which will show diverse effects.
  • Their metabolism procedure is extensive and time-consuming.

Frequently Asked Questions

What do flavonoids do for the body

Flavonoids are health-promoting and disease-preventing supplements. Flavonoids have a number of benefits for your body. They protect your body against the harmful effects of free radicals. They also include anti-inflammatory, antioxidant, anticancer, and antiviral properties.

Are flavonoids good or bad for you?

Flavonoids are generally good for your health as they have several health benefits. They have anti-inflammatory anti cancer and antiviral properties.  Besides that, if flavonoids are taken in high doses they can result in nausea, headache, and tingling of the extremities.

What are flavonoids in vitamins?

Flavonoids also known as vitamin P are found in several fruits, vegetables, grains, and herbs. They have strong neuroprotective and cardioprotective effects. They also help remove toxins from our bodies through their antioxidant effects.

When should I take flavonoids?

It is best recommended to consult your physician before taking any flavonoid supplements. 

They can be taken when needed to improve cognitive function and delay the process of aging, reduce the risk of some skin conditions, and reduce the risk of type 2 diabetes. They can also be taken by cardiac patients to boost their cardiovascular conditions.

It is best to avoid flavonoid supplements during pregnancy and lactation.


Despite a few adverse effects that flavonoids have and that are mentioned above, it is still pretty evident that their pros outweigh the cons. It is a plant-based compound. 

Flavonoid intake along with our diet is the best and the most natural way to gain all the benefits that it has. This is the reason it is recommended to increase the amount of fruits and vegetables in our diets. 

This article must be a motivation for everyone to eat healthy and healthier every day to slow their aging. This is one of the many ways to show self-care and affection to yourself.


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  2. Flavonoids. Retrieved from
  3. Flavonoids: an overview. Retrieved from
  4. Top Foods High in Flavonoids. Retrieved from
  5. How does oxidative stress affect the body? Retrieved from
  6. Flavonoids—Natural Gifts to Promote Health and Longevity. Retrieved from

About the author 

Salma is an experienced community pharmacist who's worked at multiple well-known pharmaceutical companies including Dynatis Limited and Medipak Limited

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