What are flavonoids?

Flavonoids are naturally occurring compounds found in vegetables, fruits and legumes and even in chocolate, coffee, tea and wine. They confer many health benefits due to their antioxidant, anti-inflammatory and anti-viral activity and offer protective effects on the cardiovascular and nervous systems.  You may have noticed them advertised with vitamin C as bioflavonoids or come across some of their subtypes, such as anthocyanidins, quercetin, rutin or hesperidin. But what are they and how do they help with our health?

What are flavonoids?

Flavonoids are compounds (polyphenols) found in the stems, flowers, grains, nuts and seeds of plants. They are mostly responsible for the colour and the taste of food and, in manufacturing, have been used in cosmetics, skin products and as natural dyes. They are also being applied in the field of medicine.

Flavonoids are from a large family known as polyphenolics. There are six major subclasses which are important in the human diet - anthocyanidins, flavan-3-ols, flavonols, flavanones, flavones, and isoflavones. They are classified into various types.

Anthocyanidins

Anthocyanidins (anthocyanidin, anthocyanosides) offer potent antioxidative, free-radical scavenging, anti-inflammatory and antimicrobial activity. They have been shown to improve visual and neurological health, offer a protective action beneficial in helping to prevent numerous diseases such as cardiovascular diseases, diabetes, metabolic diseases, and microbial infection.

Anthocyanidins are found in red, blue, and purple berries; red and purple grapes and red wine.

• Bilberry (Vaccinium myrtillus) extract contain contains anthocyanosides – supporting capillary and collagen function. They are beneficial for microcirculation particularly for eye health and healthy eye function.
   
• Grape Seeds supplements contain proanthocyanidins which can assist with blood and peripheral circulation, maintain healthy capillaries, collagen structure, eye health, cardiovascular system health and connective tissue health.

Flavan-3-Ols

Flavan-3-Ols include Catechins, Proanthocyanidins and Theaflavins.

• Catechins: include Epicatechin, Epigallocatechin and Gallocatechin, are found in teas, particularly white, green, and oolong; cocoa-based products; grapes, berries and apples.
• Proanthocyanidins are found in apples, berries, cocoa-based products, red grapes and red wines.
• Theaflavins are found in black tea.

Flavan-3-Ols health benefits include antioxidant, cardio-preventive, antimicrobial, anti-viral, and neuro-protective actions.

• Green tea (Camellia sinensis) dry leaf extract is available as a supplement for weight-loss. Green tea offers antioxidant, promotes energy production, enhances the process of thermogenesis, improves body metabolic rate and supports calorie burning.
   
• Cacao and cocoa are sold as supplements which can be added to food for their antioxidant value.

Flavonols

Flavonols – most studied are Fisetin, Kaempferol, Myricetin and Quercetin. Rich sources include onions, kale, lettuce, tomatoes, apples, grapes, berries, tea and red wine. Health benefits have been associated with its antioxidant potential and include a reduced risk if vascular disease.

• Quercetin is a flavone found in many foods and also supplemented as a therapeutic product. It is beneficial for allergies, cold viruses, inflammatory conditions and as antioxidant.

Flavones

Flavones – Apigenin, Luteolin, Baicalein and Chrysin, are one of the most important flavonoids. They are found in parsley, thyme, mint, chamomile, celery and red peppers and ginkgo biloba.

• Scutellaria baicalensis (Chinese skullcap) is a herb used in traditional Chinese medicine contains the flavone Baicalin, which has been shown to inhibit HIV-1 infection and replication.
   
• Ginkgo biloba (ginkgo) supports brain health, mental function and recall; supports cardiovascular and blood capillary health; maintains healthy blood circulation and is an antioxidant that reduces free radicals formed in the body.

Flavanones

Flavanones – Eriodictyol, Hesperetin and Naringenin, are another important class of flavonoids which is generally found in all types of citrus fruits - responsible also for the bitter taste of the peel. The health benefits obtained from flavanones are due to their free-radical scavenging properties, antioxidant, anti-inflammatory, blood-lipid lowering and cholesterol-lowering activity.

• Citrus flavonoids are sometimes found combined with vitamin C in supplements. They help improve the bioavailability of Vitamin C along with their own health value.
• Citrus aurantium (Bergamot) extract is an example of a supplement containing citrus polyphenols shown to support healthy cholesterol, cardiovascular system health, artery health, healthy blood circulation and healthy blood lipids.

Isoflavones

Isoflavones – (Daidzein, Genistein, Glycitein, Biochanin A, Formononetin) – found in Soybeans, soy foods and legumes offer an immense potential to fight many diseases.

Daidzein and genistein offer oestrogenic activity and are regarded as phyto-oestrogens. Genistein possesses well-known preventive activity for cardiovascular diseases and post-menopausal problems. It was shown to help with the reduction of body fat whilst on a reduced food intake diet. Genistein shown effects on hormones, lipid metabolism and supports transport of glucose into cells.

• Red clover (Trifolium pratense) isoflavones available as a supplement for the relief of symptoms of menopause including night sweats, hot flushes, and mild anxiety in post-menopausal women.

Increased intake of foods high in flavonoids can be beneficial for health.

Therapeutic value of Flavonoids

Antioxidants

Many health benefits have been attributed to a diet rich in fruit, vegetables, tea and wine - abundant with naturally-occurring flavonoids. Many of the health-promoting benefits are due to the high content of antioxidant flavonoids found in these foods. Antioxidants provide the body with natural immune protection from daily environmental and endogenous toxins created from free radicals (these guys can do some damage).

Flavonoids may offer protective effect against many diseases such as bacterial and viral disease, cardiovascular disease, diabetes, cognitive decline such as Alzheimer’s and dementia, and other age-related diseases. Flavonoids have shown to reduce the risk of coronary heart disease, offer an anti-inflammatory action, and are protective of the liver.

What foods to choose?

Including different types of flavonoids in the daily diet is highly recommended to reduce the risk of disease. A diet high in fruits and vegetables, legumes, nuts, seeds, and wholegrains is associated with many health benefits.

Suggestions of foods high in health supporting flavonoids include:

• berries, apples and citrus
• vegetables – particularly onions, kale, broccoli, peppers, celery, soybeans, soy foods and legumes
• teas - especially white, green and oolong
• cocoa-based products including chocolate, cacao and  cocoa
• white and red grapes, and red wine

The bottom line - if you want to benefit from the potential of flavonoids, add more fruits and vegetables to your diet. Supplements are available for increased health benefits. 

References

1. Flavonoids: an overview https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5465813/
2. Chemistry and Biological Activities of Flavonoids: An Overview https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3891543/
3. Important Flavonoids and Their Role as a Therapeutic Agent https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7697716/
4. Flavonoids in food and their health benefits https://pubmed.ncbi.nlm.nih.gov/15678717/
5. Flavonoid-rich foods (FRF): A promising nutraceutical approach against lifespan-shortening diseases https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7211351/
6. Flavan-3-ols: nature, occurrence and biological activity https://pubmed.ncbi.nlm.nih.gov/18081206/#
7. https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids#subclasses
8. Anthocyanidins and anthocyanins: colored pigments as food, pharmaceutical ingredients, and the potential health benefits https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613902/
9. Genistein--a dietary compound inducing hormonal and metabolic changes https://pubmed.ncbi.nlm.nih.gov/17588743/
10. The Therapeutic Potential of Apigenin https://pubmed.ncbi.nlm.nih.gov/30875872/
11. Grape Seeds Proanthocyanidins: An Overview of In Vivo Bioactivity in Animal Models https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835351/
12. Anthocyanosides of Vaccinium myrtillus (bilberry) for night vision--a systematic review of placebo-controlled trials https://pubmed.ncbi.nlm.nih.gov/14711439/
13. https://bergamet.com.au/
14. https://bergamet.com.au/clinical-studies/