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Phenols are a broad class of aromatic organic compounds manufactured by plants that can be strong systemic poisons for organisms including animals, bacteria, fungi, parasites and viruses. Phenolic compounds are stored in the tissues of plants to deter plant browsers and are released when plant material decomposes or is damaged. They are also involved in defence against attacks by pathogens and ultraviolet radiation.

Poly means many, which refers to the large number of groupings of the basic phenol rings. There are over 4,000 polyphenol compounds. Many are powerful antioxidants and can neutralise free radicals, reduce inflammation and slow the growth of tumours.

Various polyphenols provide the colours of ripe plums and berries and the intense colours of geraniums and delphiniums.

A polyphenol antioxidant is a type of antioxidant containing a polyphenolic or natural phenol substructure. Anthocyanins, flavonoids, tannins, resveratrol (found in grapes and cocoa) and catechins (such as epigallocatechin gallate (found in green tea) are all polyphenol compounds. Consuming foods rich in polyphenols can be beneficial to those suffering with diabetes or infections.

Polyphenols are reducing agents and together with other dietary reducing agents, such as carotenoids, vitamins C and vitamin E, referred to as antioxidants, protect the human body's tissues against oxidative stress and associated pathologies such as cancers, coronary heart disease and inflammation. Polyphenols are the most abundant antioxidants in the diet and the main classes of polyphenols are phenolic acids, mainly caffeic acid and flavonoids.

Examples of polyphenols

  • Capsaicin in chilli and paprika.

  • Cinnamic acid in cinnamon.

  • Ferulic acid in cereal grains,

  • Punicalagins in pomegranates.

  • Resveratrol in red wine.

  • Rosmarinic acid found in rosemary, thyme, oregano, sage and peppermint.

  • Thymol in thyme.


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Highest sources of polyphenols in milligrams per 100 grams

  • Cloves 15188 mg

  • Peppermint 11960 mg

  • Star anise 5460 mg

  • Cocoa powder 3448 mg

  • Mexican oregano 2319 mg

  • Celery seed 2094 mg

  • Black chokeberry 1756 mg

  • Dark chocolate 1664 mg

  • Flaxseed meal 1528 mg

  • Black elderberry 1359 mg

  • Chestnuts 1215 mg

  • Sage 1207 mg

  • Rosemary 1018 mg

  • Spearmint 956 mg

  • Common thyme 878 mg

  • Lowbush blueberry 836 mg

  • Blackcurrant 758 mg

  • Capers 654 mg

  • Black olive 569 mg

  • Highbush blueberry 560 mg

  • Hazelnuts 495 mg

  • Pecan nuts 493 mg

  • Soy flour 466 mg

  • Plums 377 mg

  • Green olives 346 mg

  • Sweet basil 322 mg

  • Curry powder 285 mg

  • Sweet cherry 274 mg

  • Globe artichoke heads 260 mg

  • Blackberry 260 mg

  • Milk chocolate 236 mg

  • Strawberry 235 mg

  • Red chicory 235 mg

  • Red raspberry 215 mg

  • Coffee 214 mg

  • Ginger 202 mg

  • Prunes 194 mg

  • Almonds 187 mg

  • Black grapes 169 mg

  • Red onions 168 mg

  • Green chicory 166 mg

  • Thyme 163 mg

  • Maize flour 153 mg

  • Tempeh 148 mg

  • Star fruit 143 mg

  • Whole grain rye flour 143 mg

  • Apples 136 mg

  • Peaches 134 mg

  • Guava 126 mg

  • Spinach 119 mg

  • Kiwi fruit 116 mg

  • Loquat 106 mg

  • Pomegranate juice 104 mg

  • Shallots 113 mg

  • Lemon verbena106 mg

  • Mango 104 mg

  • Black tea 102 mg

  • Red wine 101 mg

  • Green tea 89 mg

  • Banana 78 mg

  • Onions 74 mg

  • Whole grain wheat flour 71 mg

  • Apple juice 68 mg

  • Extra-virgin olive oil 62 mg

  • Pineapple 61 mg

  • Black beans 59 mg

  • Papaya 58 mg

  • Blood orange juice 56 mg

  • Cumin 55 mg

  • Grapefruit juice 53 mg

  • White beans 51 mg

  • Chinese cinnamon 48 mg

  • Orange juice 46 mg

  • Broccoli 45 mg

  • Redcurrants 43 mg

  • Lemon juice 42 mg

  • Whole grain oat flour 37 mg

  • Apricots 34 mg

  • Caraway seeds 33 mg

  • Refined rye flour 31 mg

  • Asparagus 29 mg

  • Walnuts 28 mg

  • Potatoes 28 mg

  • cinnamon 27 mg

  • Parsley (dried) 25 mg

  • Nectarines 25 mg

  • Curly endive 24 mg

  • Marjoram (dried) 23 mg

  • Red lettuce 23 mg

  • Chocolate milk beverage 21 mg

  • Quince 19 mg

  • Endive (Escarole) 18 mg

  • Pomelo juice 18 mg

  • Rapeseed oil 17 mg

  • Pears 17 mg

  • Soybean sprouts 15 mg

  • Green grapes 15 mg

  • Carrots 14 mg

  • Vinegar 13 mg

  • White wine 10 mg

  • Rosé wine 10 mg

NOTE: Some foods high in polyphenols are also high in harmful lectins, such as foods in the nightshade family and various beans.

Beans high in lectins

  • Caster

  • Cocoa

  • Coffee

  • Lentils

  • Navy beans

  • Peanuts

  • Soya beans

Foods in the nightshade family high in lectins

  • Ashwaganda

  • Aubergines

  • Blueberries

  • Goji berries

  • Huckleberries

  • Peppers

  • Potatoes

  • Tomatoes.

Structure of polyphenols

Polyphenols are divided into four primary groups:

  • Flavonoids

  • Lignans

  • Phenolic acids

  • Stilbenes


Flavonoids are divided in six groups

  1. Anthocyanidins

  2. Flavanols

  3. Flavonols

  4. Flavanones

  5. Flavones

  6. Isoflavones

1. Anthocyanidins

Anthocyanidins are associated with heart health, antioxidant effects and helping with obesity and diabetes prevention.

Types of anthocyanins

  • Apigeninidin

  • Aurantinidin

  • Capensinidin

  • Cyanidin

  • Delphinidin

  • Europinidin

  • Hirsutidin

  • Luteolinidin

  • Malvidin

  • Pelargonidin

  • Peonidin

  • Petunidin

  • Pulchellidin

  • Rosinidin

  • Tricetinidin


Highest sources of anthocyanidins in alphabetical order

  • Acai berry

  • Apples (red)

  • Aubergine

  • Beans (black and red)

  • Beetroot

  • Bilberries

  • Blackberries

  • Black currants

  • Black rice

  • Blueberries

  • Broccoli tops (purple)

  • Cabbage (red)

  • Cherries

  • Chokeberries

  • Cranberries

  • Elderberries

  • Grapefruit (pink)

  • Grapes (black and red)

  • Kidney beans

  • Maqui berries

  • Mulberries

  • Onions (red)

  • Oranges (blood)

  • Pears (red)

  • Plums

  • Potatoes (red skinned)

  • Pomegranates

  • Radishes (red)

  • Raspberries

  • Rhubarb

  • Rosehips

  • Saw palmetto berries

  • Strawberries

  • Sumac

  • Sweet potato (purple variety)

  • Swiss chard

  • Wine (red)

  • Winged beans


Find out more about anthocyanidins

2. Flanan-3-ols

Catechins can reduce chronic fatigue syndrome symptoms and are also associated with cardiovascular and neurological health.

Types of flavonols

  • Dimers

  • Monomers (Catechins)

  • Polymers

  • Theaflavins

  • Thearubigins

Highest sources of flava-3-nols in alphabetical order

  • Apples

  • Apricots

  • Berries

  • Broccoli

  • Grapes (red)

  • Kale

  • Onions

  • Scallions

  • Teas (black, green, oolong and white)

Dimers and polymers (proanthocyanidins) are found in apples, berries, cocoa-based products, red grapes and red wine.


Molymers (catechins) are found in apples, apricots, berries, cocoa beans, grapes and teas  (green, oolong and white). Apricots are the richest source of catechins.


Theaflavins and thearubigins are found in black tea.

3. Flavonols

Quercetin is an antihistamine associated with helping to relieve hay fever and hives. It is also known for its anti-inflammatory benefits. Kaempferol, and other flavan-3-ols, are associated with powerful anti-inflammatory and antioxidant activities leading to chronic disease prevention.

Types of flavonols

Highest sources of flavonols in alphabetical order

  • Apples

  • Berries

  • Cocoa beans

  • Grapes

  • Teas (green, oolong and white)

4. Flavanones

Flavanones are associated with anti-inflammatory activity and antioxidant, cardiovascular health and relaxation.

Types of flavanones

  • Eriodictyol

  • Heridictyol

  • Hesperidin

  • Hesperitin

  • Isosakuratenin

  • Naringin

  • Naringenin

  • Narirutin

  • Neohesperidin

  • Neoeriocitrin


Highest sources of flavanones on alphabetical order

  • Grapefruit

  • Lemon

  • Lime

  • Oranges

  • Pomelo

  • Tangerines

5. Flavones

Flavones are associated with antioxidant benefits and delaying the metabolising of drugs.

Types of flavones

  • Apigenin

  • Baicalein

  • Chrysin

  • Luteolin

Highest sources of flavones in alphabetical order

  • Celery

  • Parsley

  • Peppers (hot)

  • Thyme

6. Isoflavones

Isoflavones are phyto-oestrogens, meaning that they are chemicals that act like the hormone oestrogen. They may be useful for treating some hormonal issues in women but they may cause issues with the thyroid glands and therefore should be consumed in moderation.

Types of isoflavones

  • Biochanin A

  • Daidzein

  • Formononetin

  • Genistein

  • Glycitein

Highest sources of isoflavones in alphabetical order

  • Legumes

  • Soya products


Lignans consist of enterolactone, sesamin and enterodiol and can protect against breast cancer in women. The body converts lignans into chemicals with some oestrogen-like effects. Sesamin is a lignan which can help to reduce fat. Lignans also have anticancer, antibacterial and antiviral activity.

Natural sources of lignans

  • Algae

  • Asparagus

  • Bamboo shoots

  • Barley

  • Berries

  • Bran

  • Broccoli

  • Carrots

  • Cashew nuts

  • Fagara

  • Flaxseeds and oil

  • Garlic

  • Kale

  • Lentils

  • Nutmeg

  • Pears

  • Prunes

  • Sesame seeds and oil

  • Sunflower seeds

  • Triticale

  • Wheat

NOTE: Flaxseeds are the richest source of lignans.

Phenolic acid

Two classes of phenolic acids can be distinguished:

  • Hydroxybenzoic acid

  • Hydroxycinnamic acid

Components of hydroxybenzoic acid

  • Ellagitannins in fruits such as blackberries, raspberries and strawberries

  • Gallic acid in tea leaves

  • Gallotannins in mangoes

Components of hydroxycinnamic acid

  • Caffeic acid

  • Coumaric acid

  • Ferulic acid

  • Quinic acid

  • Shikimic acid

  • Sinapic acid

  • Tartaric acid

Caffeic acid is found in all plants because it is a key intermediate in the biosynthesis of lignin. It possesses cancer preventing and anti-tumour properties and reduces body weight, lipid metabolism and obesity-related hormone levels.  It can also boost athletic performance, reduce exercise-related fatigue and help with the treatment of herpes, HIV/AIDS and other virus infections.

Highest sources of caffeic acid


Caffeic and quinic acid combine to form chlorogenic acid, which is found in many types of fruit and in high concentrations in coffee

Highest sources of phenolic acid

  • Blueberries

  • Coffee beans

  • Kiwi fruits

  • Onions (red)

  • Radishes (black)

  • Tea


Stilbenes are found in only low quantities in the human diet. One of these, resveratrol, for which anti-carcinogenic effects have been shown during screening of medicinal plants and which has been extensively studied, is found in low quantities in wine. However, because resveratrol is found in such small quantities in the diet, any protective effect of this molecule is unlikely at normal nutritional intakes.

Phenol intolerance

Many synthetic food additives are now derived from petroleum or crude oil such as

  • Butylated hydroxyanisole (BHA) E321

  • Butylated hydroxytoluene (BHT) E392

  • Tertiary butylhydroquinone (TBHQ) E320

Tertiary butylhydroquinone (TBHQ) is an aromatic organic compound which is a type of phenol used as a food preservative which is a form of butane. It is also used in the stabilisation process of explosive compounds. It can be found as an additive in the following products:

  • Cosmetic skincare products for adults and babies.

  • Crackers

  • Crisps

  • Fast foods

  • Lacquers

  • Pet foods

  • Resins

  • Varnish

Consuming high doses (1-4 g) of tertiary butylhydroquinone can cause the following symptoms:

  • Asthma

  • Collapse

  • Delirium

  • Dermatitis

  • Hyperactivity in children

  • Nausea and vomiting

  • Restlessness

  • Rhinitis (inflammation inside the nose)

  • Tinnitus (ringing in the ears)

It may also aggravate attention deficit hyperactivity disorder (ADHD symptoms). It can also affect oestrogen levels in women.

Phenolic compounds are regularly found throughout the environment in thousands of items including most foods, pollen and chemicals. Many forms of asthma are caused by allergic reactions from both airborne phenolic compounds and those found in foods. It is difficult to avoid phenols as one of them, gallic acid, occurs in about 70% of the foods humans consume.

If there is no improvement to symptoms through the elimination of phenols then check that the intolerance is not to the other food allergens listed on this page: Allergies

Associated subjects

"Nature cures not the physician..." Hippocrates 460 BC


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