WHAT ARE THE FLAVONOIDS?
The flavonoids (also known as bioflavonoids, polyphenols or vitamin P) are probably the most well known group of phytonutrients (a group of chemical compounds which occur naturally in plants and have numerous health benefits but are not considered essential nutrients). The flavonoid group is comprised of 9 separate sub-groups:
– Anthocyanins (which include cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin).
– Coumestans (which include coumestrol).
– Flavanones (which include hesperidin, naringenin and silymarin).
– Flavanonols (which include taxifolin).
– Flavan-3-ols (which include catechin, epicatechin, gallocatechol, epigallocatechin gallate, epicatechin gallate, theaflavin and thearubigins).
– Flavones (which include apigenin, luteolin and tangeretin).
– Flavonols (which include gingerol, isorhamnetin, kaempferol, myricetin, rutin and quercetin).
– Isoflavones (which include daidzein and genistein).
The flavonoids were first discovered and isolated in 1938 by the Hungarian biochemist Albert Szent-Györgi. He initially believed that the flavonoids were a vitamin (as they possess vitamin like properties) and so named them vitamin P. However, it was later discovered that flavonoids are not essential to human health and therefore not technically vitamins (although they are still sometimes unofficially classified as water soluble vitamins today).
Although the flavonoids are not believed to be essential in humans, there is a growing body of evidence which suggests consuming these plant based nutrients can provide significant health benefits. Most notably they are highly potent antioxidants which can protect your body’s cells from damaging free radicals (harmful by-product that are released during oxygen related reactions) and indirectly offer further protection against a variety of diseases and health conditions.
In this article I will be discussing the 9 flavonoid sub-groups in greater detail:
Functions:- The anthocyanins act as powerful anti-inflammatories (substances which prevent unnecessary inflammation within the human body), antioxidants and antitoxics (substances which fight harmful toxins within the body). They also have cancer fighting properties and can prevent colon cancer, lung cancer, prostate cancer and skin cancer. Additionally, the anthocyanins can assist in the treatment of type 2 diabetes (by reducing blood glucose levels and increasing insulin sensitivity within the body) and prevent atherosclerosis (a condition where hard plaques form in your artery walls and restrict the flow of blood).
Recommended Daily Allowance (RDA):- There is currently no RDA for the anthocyanins.
Food Sources:- Berries are often the best source of anthocyanins. Blueberries in particular are an excellent source and contain 16.97 milligrams (mg) of cyanidin, 47.4mg of delphinidin, 61.35mg of malvidin, 23.49mg of peonidin and 26.42mg of petunidin per 100 grams (g).
Overdose Symptoms:- There are no reported overdose symptoms associated with anthocyanin consumption.
Deficiency Symptoms:- There are no reported deficiency symptoms associated with anthocyanin consumption.
Functions:- The chalconoids are powerful antibacterials (substances which kill or slow the growth of bacteria), antifungals (substances which treat fungal infections), antimicrobials (substances which kill or slow down the growth of microorganisms) and antioxidants. Additionally, they prevent a variety of diseases and disorders including acne, Alzheimer’s disease (a mental disorder which leads to the loss of memory, thought and speech), cancer, diabetes and heart disease.
RDA:- There is currently no RDA for the chalconoids.
Food Sources:- There is little information available on the exact amounts of chalconoids in specific foods. However, they can be found in the leaves of ashitaba, eucalyptus and liquorice plants.
Overdose Symptoms:- There are no reported overdose symptoms associated with chalconoid consumption.
Deficiency Symptoms:- There are no reported deficiency symptoms associated with chalconoid consumption.
Functions:- Comestans act as phytoestrogens (compounds which regulate estrogen levels in the body and help prevent cancer, heart disease, osteoporosis (reduced bone mineral density) and negative menopausal symptoms) and also prevent cancer.
RDA:- There is currently no RDA for coumestans.
Food Sources:- Alfalfa, peas, soya beans and red clover are all great sources of coumestans. Green peas are a particularly rich source of coumestrol and contain 6.25mg per 100g.
Overdose Symptoms:- There are no reported overdose symptoms associated with coumestan consumption.
Deficiency Symptoms:- There are no reported deficiency symptoms associated with coumestan consumption.
Functions:- The flavanones are powerful antioxidants which also protect against cancer, treat diabetes and strengthen the immune system. In addition to this, they keep your blood and blood vessels healthy by acting as a hypolipidemic (a substance which lowers the levels of lipids in the blood) and reducing blood levels of low density lipoprotein (LDL) cholesterol (a type of cholesterol which can cause blockages in the arteries). Finally, the flavanones support a healthy liver by acting as an antihepatoxic (a substance which protects the liver from various types of damaging toxins), reducing the production of the hepatitis C virus (a type of virus which damages the liver and causes liver inflammation), supporting the production of new liver cells and treating various liver diseases.
RDA:- There is currently no official RDA for the flavanones. However, some studies suggest that you should try to consume between 10mg and 100mg of hesperidin and between 280mg and 420mg of silymarin each day to realise all the health benefits of these flavanones.
Food Sources:- Citrus fruits often contain the highest levels of flavanones. Oranges are thought to be 1 of the best sources available with 100g of this fruit supplying your body with 27.25mg of hesperidin and 15.32mg of naringenin.
Deficiency Symptoms:- Failing to consume at least 10mg of hesperidin each day can lead to abnormal capillary bleeding, leg cramps, pain in the extremities and weakness.
Overdose Symptoms:- There are no reported overdose symptoms associated with flavanone consumption but some people are allergic to silymarin. This can lead to a number of allergic reactions such as breathing difficulties, closing of the throat, diarrhea and hives (a type of skin rash).
Functions:- The flavanonols are potent antihistamines (substances which counteract the effects of histamine and reduce allergic symptoms), anti-inflammatories and antioxidants. They can also keep your blood healthy by improving circulation, preventing atherosclerosis, reducing blood levels of LDL cholesterol and reducing high blood pressure. Finally, the flavanonols can prevent cancer and diabetes.
RDA:- There is currently no official RDA for the flavanonols. However, certain studies suggest that consuming between 50mg and 1,000mg of taxifolin each day will allow you to enjoy the health benefits of this specific flavanonol.
Food Sources:- Milk thistle and red onion are the best flavanonol foods. However, the exact amounts in these foods are not known.
Overdose Symptoms:- There are no reported overdose symptoms associated with flavanonol consumption.
Deficiency Symptoms:- There are no reported deficiency symptoms associated with flavanonol consumption.
Functions:- The flavan-3-ols are powerful antihistamines and antioxidants. They have also been linked with the prevention of various diseases and mental disorders including Alzheimer’s disease, cancer, diabetes, dementia (a form of mental deterioration), hepatitis and Parkinsons’s disease (a degenerative brain disease which causes loss of mobility and speech). Additionally, the flavan-3-ols keep the blood healthy by preventing arteriosclerosis (the hardening and loss of elasticity within the arteries), preventing high blood pressure and reducing blood levels of LDL cholesterol.
RDA:- There is currently no official RDA for the flavan-3-ols. However, research suggests that consuming approximately 20mg of epicatechin, 2,000mg of epigallocatechin gallate and 8mg of theaflavin will allow you to unlock the health benefits of these flavan-3-ols.
Food Sources:- Dark chocolate and tea are extremely rich in the flavan-3-ols. A 100g serving of dark chocolate provides you with 11.99mg of catechin and 41.5mg of epicatechin whilst a 100 millilitre (ml) serving of green tea provides you with 2.55mg of catechin, 8.29mg of epicatechin, 77.81mg of epigallocatechin gallate, 20.95mg of epicatechin gallate and 1.03mg of theaflavin.
Overdose Symptoms:- Overdosing on epigallocatechin gallate can interfere with its ability to fight cancer and free radicals whilst consuming too much epicatechin gallate can stimulate tumour growth. Therefore, it is recommended that you consume no more than 4,000mg of epigallocatechin gallate and 200mg of epicatechin gallate per day.
Deficiency Symptoms:- There are no official deficiency symptoms associated with flavan-3-ol consumption. However, Dr Norman Hollenberg has suggested that failing to consume enough epicatechin may cause cancer, diabetes, heart failure and stroke.
Functions:- The flavones are potent antioxidants, antihistamines, anti-inflammatories and antispasmodics (substances which prevent muscle spasms). They also act in a protective capacity by preventing allergies, brain damage, cancer, diabetes, respiratory disorders and vision disorders. Additionally, the flavones keep the blood healthy by preventing atherosclerosis, reducing blood levels of LDL cholesterol and strengthening the capillaries.
RDA:- There is currently no official RDA for the flavones.
Food Sources:- The flavones can be found in various herbs, spices and green leafy vegetables. Some of the best food sources are parsley (which contains 225.93mg of apigenin per 100g), thyme (which contains 45.25mg of luteolin per 100g) and oranges (which contain 0.3mg of tangeretin per 100g).
Overdose Symptoms:- Eating high levels of apigenin can reduce the effectiveness of certain cancer treatments. Additionally, overdosing on luteolin can lead to gastric hypersecretion (excessive formation of gastric juices), nausea and vomiting.
Deficiency Symptoms:- Currently there are no reported deficiency symptoms associated with flavone consumption.
Functions:- The flavonols are powerful antidepressants, antihistamines, antioxidants and phytoestrogens. They are also highly protective against cancer and can help fight breast cancer, colon cancer, esophageal cancer, liver cancer, lung cancer, ovarian cancer, pancreatic cancer and prostate cancer. Additionally, the flavonols can assist in the treatment of other health conditions such as arthritis (inflammation of the joints), atherogenesis (the formation of plaques on the artery walls), diabetes, haemophilia (a condition which causes uncontrollable bleeding), heart problems, mental disorders, migraines, nausea and venous edema (a condition which causes swelling in the lower legs). Finally, they can boost your metabolism (by supporting the production of the metabolism boosting hormone triiodothyronine which is also known as T3), enhance the effectiveness of vitamin C, increase energy and endurance during exercise, improve blood circulation, prevent arteriosclerosis, reduce blood levels of LDL cholesterol and strengthen the capillaries.
RDA:- There is currently no official RDA for the flavonols. However, certain studies suggest that you should try and consume between 10mg and 12mg of kaempferol, between 200mg and 600mg of rutin and between 200mg and 500mg of quercetin each day to enjoy all the health benefits of these flavonols.
Food Sources:- The flavonols can be found in a wide variety of plant based foods such as herbs, fruits, vegetables and teas. 2 of the best flavonol food sources are black tea (which contains 1.31mg of kaempferol and 1.99mg of quercetin per 100g) and cranberries (which contain 6.78mg of myricetin and 14.02mg of quercetin per 100g).
Overdose Symptoms:- Overdosing on gingerol supplements can lead to confusion, dizziness and irregular heartbeats whilst consuming high levels of kaempferol and myricetin can lead to allergic reactions and interference with other medications and supplements. Eating high levels of rutin can cause dizziness, fatigue, headaches, muscle stiffness, rapid heartbeats and stomach upsets whilst overdosing on quercetin can cause diarrhea, headaches, interference with anticoagulants (which can lead to uncontrollable bleeding) and kidney damage.
Deficiency Symptoms:- Currently there are no reported deficiency symptoms associated with flavonol consumption.
Functions:- The isoflavones act as powerful anthelmintic s (substances which remove parasitic worms from the body), antioxidants and phytoestrogens. They also protect against various types of cancer (particularly breast cancer and prostate cancer), prevent diabetes and support the production of osteoblasts (cells that produce bone mass).
RDA:- There is currently no official RDA for the isoflavones. However, a number of studies suggest that consuming between 50mg and 100mg of isoflavones each day will allow you to activate the health benefits listed above.
Food Sources:- Soybeans and soy based products often contain the highest levels of isoflavones. 2 of the richest food sources are green soybeans (which contain 67.79mg of daidzein and 72.51mg of genistein per 100g) and soy protein isolate (which contains 33.59mg of daidzein and 59.62mg of genistein per 100g).
Overdose Symptoms:- Currently there are no reported overdose symptoms associated with isoflavone consumption. However, provisional research suggests that eating high levels of isoflavones may increase your cancer risk. Additionally, certain people are allergic to isoflavones and for these people consuming high levels can cause interference with mineral absorption and thyroid function.
Deficiency Symptoms:- Currently there are no reported deficiency symptoms associated with isoflavone consumption.
As you can see, the flavonoids are very important nutrients that can protect your body from many diseases, keep your cells strong, support vital functions and much more. Although they are not considered essential to human health, you should not neglect these powerful plant based nutrients. Fruits, herbs, vegetables and teas are all low in calories, rich in flavonoids and contain high levels of many other important nutrients.
Despite this, many people do not consume enough flavonoid rich foods. So if your diet is currently lacking in any of the foods listed above try to start including them as soon as possible. Fruits make great snacks, herbs are an excellent way to spice up a meal, vegetables are a brilliant way to add consistency to a dish and tea is a really healthy way to stay hydrated.