Polyphenol and Flavonoid Foods: A List

Three things first

• Spices and herbs carry the most antioxidants per 100 grams, followed by berries, cocoa, nuts and dark leafy greens. In daily life, though, what counts is the amount you actually eat: berries, cabbage, onions, tea and coffee.
• A plant compound is not a goal. Nobody wants “more quercetin”; people want a body that works well. That is why this article shows, for every compound, which nutrition goal it counts towards in the app.
• Variety beats superfoods. Every plant family brings different compounds. Five different colours on the plate cover more than the biggest portion of a single food.

What are phytonutrients — and are phytonutrients antioxidants?

Plants make phytonutrients (secondary plant compounds) to protect themselves from sun, pests and disease, and to get their colour, scent and taste. “Secondary” only means that the plant does not need them to grow, unlike protein, fat or carbohydrates. Tens of thousands of these compounds are known; a few thousand occur in our food.

The largest groups are:

• Polyphenols — the largest family. It includes the flavonoids (for example quercetin, anthocyanins, catechins from tea and cocoa), phenolic acids (caffeic acid, gallic acid, ellagic acid), lignans from seeds, and resveratrol.
• Carotenoids — the yellow, orange and red pigments, such as lycopene from tomatoes.
• Sulphur compounds — glucosinolates from cabbage (sulforaphane forms from them) and alliin from garlic and onions.
• Others, such as curcumin from turmeric or the secoiridoids from olives.

Antioxidant is not the name of a compound but a property: in a test tube, the substance neutralises free radicals. Many phytonutrients can do this, and so can vitamin C and vitamin E. In the body, many plant compounds probably act less as direct radical scavengers and more as a signal: they switch on the body’s own protective systems. Sulforaphane from broccoli is the best-studied example.

Which foods are highest in antioxidants and polyphenols?

Two large sets of measurements give the answer. A Norwegian group measured the antioxidant content of more than 3100 foods: spices and herbs led by a wide margin, followed by berries, fruit, nuts, chocolate and vegetables. The French Phenol-Explorer database counts the individual polyphenols and used them to identify the 100 foods that contain the most:

• Spices and dried herbs lead, above all cloves at around 15,000 milligrams per 100 grams, along with dried peppermint, star anise, oregano and celery seed.
• Cocoa: cocoa powder and dark chocolate.
• Dark berries such as aronia, black elderberry, blackcurrants and blueberries.
• Seeds and nuts: flaxseed, chestnuts and hazelnuts.
• Vegetables: above all olives and artichokes.

Per serving, the list looks different. Nobody eats 100 grams of cloves. With usual amounts, the foods that move up are the ones eaten often and in larger quantities: berries, coffee, tea, apples, artichokes and nuts.

Whether a high intake goes with a longer life was studied in a Danish cohort of more than 56,000 people. Over 23 years, people who ate more flavonoids had a lower risk of death. The association grew stronger up to about 500 milligrams a day and then levelled off — roughly a cup of tea, an apple, an orange, 100 grams of blueberries and 100 grams of broccoli. This is an association from an observational study, not proof of cause and effect.

Which phytonutrients are there, and which foods carry them?

The Food Secrets catalogue records 20 plant compounds for more than 1000 foods. For five of them, good measurement data confirm our values. For those we name the food that leads. For the others we name the food groups in which they occur.

Kaempferol, myricetin, phenolic acids, thymoquinone

Kaempferol is found in watercress, rocket, kale and capers, myricetin in parsley and goji berries. Caffeic acid comes mostly from coffee, gallic acid from chestnuts, cloves and strawberries. Thymoquinone occurs almost only in black seed oil; it counts towards Allergy and Antimicrobial. In the Food Lab you can sort by each of these compounds as its own column.

How much sulforaphane is in broccoli and broccoli sprouts?

Broccoli does not contain finished sulforaphane. The plant stores a precursor, glucoraphanin, and an enzyme, myrosinase. Only when you cut or chew it do the two meet, and sulforaphane forms.

• Sprouts have many times more. In the first measurements, three-day-old broccoli sprouts contained 10 to 100 times more glucoraphanin than mature broccoli.
• Raw or briefly cooked is better. In one study the body absorbed around 37 per cent of the sulforaphane from raw broccoli, but only around 3 per cent from well-cooked broccoli. Long cooking destroys the myrosinase.
• Chop and wait a moment. Chopping broccoli and letting it rest for a few minutes before steaming gives the enzyme time.

In the app, the Digestion & Liver rank has broccoli sprouts in the top 10. What sulforaphane measurably does for the liver is covered in the article Liver detox foods: what really helps.

How more ends up on your plate

• Tomatoes with oil and heat. In one study, blood lycopene after tomato paste was two and a half to almost four times higher than after fresh tomatoes, both eaten with a little oil. Lycopene is fat-soluble, so a splash of olive oil belongs with it.
• Turmeric with pepper. With piperine from black pepper, curcumin absorption in humans rose many times over — in one study by around 2000 per cent.
• Chop garlic and let it rest. As with broccoli, the active compound only forms through an enzyme once the cells are damaged.
• Olive oil with a bite. Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress — one of the few authorised EU health claims on plant compounds. It applies to oils with at least 5 mg of hydroxytyrosol and related compounds per 20 grams. A fresh, slightly bitter oil that catches in the throat usually has more of them.
• Eat the skin and the colour. Many plant compounds sit in the skin and the outer leaves: apple peel, the red layers of onions, dark cabbage leaves.

What phytonutrients count towards in the app

In the Food Secrets app, a plant compound is a building block, not a goal of its own. Every rank uses the compounds that fit its goal. In the Immune system and Weight loss ranks, 14 plant compounds count together as one building block. The Longevity rank works through the body’s five defence systems, not through single compounds.

One example is the Inflammation rank. It scores more than 1000 foods; quercetin and anthocyanins count in it, alongside omega-3 fatty acids, fibre and other nutrients. This is where plant foods rich in phytonutrients land:

• Top 10: walnuts, oregano, peppermint, cranberries, watercress and elderberries.
• Top 20: turmeric, blackcurrants, cocoa powder, kale and raspberries.
• Top 50: blueberries, cinnamon, broccoli sprouts, garlic, blackberries, olive oil, raw broccoli and aronia.
• Top 100: strawberries, parsley, capers, cloves, red chicory and rocket.

You will find the full list and all the other goals in the Food Rankings. How phytonutrients relate to medicinal herbs and spices is shown on the page Active compounds in food.

Berries and the heart

In a US cohort of more than 93,000 young and middle-aged women, those with the highest anthocyanin intake had a risk of heart attack around 32 per cent lower over 18 years than those with the lowest. Women who ate three or more servings of blueberries and strawberries a week pointed the same way. This too is an association, not proof — but it fits with what berries bring to Inflammation and Blood pressure in the app.

The recipe for this article

Blueberries for the anthocyanins, cocoa for the flavanols, plus chia and pumpkin seeds: the blueberry chia pudding with cocoa and pumpkin seeds brings several groups of phytonutrients into one bowl, and you prepare it the evening before. More recipes by goal are in the recipe collection.

Find phytonutrients in daily life

The app shows which plant compounds each food brings and sorts by your goals.

Frequently asked questions — polyphenols, flavonoids and antioxidant foods

More on this topic

• Active compounds in food – phytonutrients, herbs and spices at a glance.
• Anti-inflammatory diet – what goes on the plate when inflammation is the topic.
• Liver detox foods: what really helps – what broccoli sprouts and fibre measurably do.
• Food Rankings – more than 1000 foods by 15 health goals.
• Blueberry chia pudding with cocoa and pumpkin seeds – the recipe for this article.

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