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Deutsch (EUR)Polyphenols: What They Are, Where They Are Found and Which Foods Contain Them
Polyphenols: What They Are, Where They Are Found and Which Foods Contain Them
Tea, coffee, berries, cocoa and olives contain different polyphenols. This overview explains what polyphenols are, where they are found, and how to distinguish information about foods from research on concentrated extracts.
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What are polyphenols?
Polyphenols are a diverse group of naturally occurring plant compounds. Commonly described groups include flavonoids, phenolic acids, stilbenes and lignans. A single food usually contains several different compounds. Their amounts depend on variety, ripeness, growing conditions, storage and processing.
Which foods contain polyphenols?
Blueberries, blackberries, apples, grapes, citrus fruit and onions.
Green and black tea, coffee, cocoa and cocoa-containing products.
Olives, virgin olive oil, walnuts, hazelnuts, flaxseeds and sesame seeds.
Pulses, some cereals, herbs and spices, including cloves.
Which sources contain the most polyphenols?
A ranking per 100 g of food is not the same as the amount in a typical serving. Spices may have a high content per 100 g, but are used in small quantities. Tea preparation also matters. Values obtained using different analytical methods are not always directly comparable. It is therefore misleading to name one food as the universally “best source”.
Polyphenols and antioxidants: what is the difference?
Polyphenol refers to a group of chemical compounds; antioxidant describes the ability to limit oxidation under certain conditions. Some polyphenols show antioxidant activity in laboratory tests. This alone does not demonstrate cell protection, an anti-inflammatory effect or disease prevention after consuming a particular food or extract. Not all antioxidants are polyphenols.
Examples of polyphenols
Pigments found, for example, in dark-coloured berries.
Found, for example, in green tea; EGCG is one of them.
A stilbene found, for example, in grapes.
Dietary sources include flaxseeds.
Polyphenols and the gut microbiome
Some ingested polyphenols and their metabolites reach the large intestine, where gut microorganisms can transform them further. Absorption and these transformations vary between individuals. Research into these processes does not establish that a particular product “restores the microbiome” or treats digestive diseases.
Food and concentrated extracts
Food provides a mixture of compounds alongside other food components. A concentrated extract can have a different composition, dose and safety profile. In its assessment of green tea catechins, EFSA identified concerns about possible liver damage with high doses of EGCG in supplements. Conventionally brewed tea should therefore not automatically be equated with an extract. Consult a doctor or pharmacist about concentrated extracts if you take medicines, are pregnant or have liver disease.
How to read polyphenol research
Check the exact compound or extract, dose, duration, number of participants and measured outcome. Laboratory experiments, observational studies and controlled human studies provide different types of evidence. Findings from a particular study cannot be extended to all polyphenols or any product. For health claims, check the exact wording and conditions of use in the EU register.
Frequently asked questions
What are polyphenols and where are they found?
They are plant compounds found, for example, in fruit, vegetables, tea, coffee, cocoa, olives, nuts and seeds.
Is resveratrol a polyphenol?
Yes. It belongs to the stilbenes, and grapes are one of its dietary sources.
Is an extract better than a food?
This cannot be assumed. A higher concentration does not automatically mean greater benefit or better safety.
Are polyphenols and antioxidants the same thing?
No. Polyphenols are a group of compounds; antioxidant activity is a property that depends on conditions. A laboratory result is not proof of a therapeutic effect.
Do I need to drink red wine to obtain polyphenols?
No. Many non-alcoholic foods and drinks contain polyphenols. This article does not recommend alcohol as a source.
References
- Phenol-Explorer — Database on Polyphenol Content in Foods
- Pérez-Jiménez et al. (2010): Identification of the 100 richest dietary sources of polyphenols
- Di Lorenzo et al. (2021): Polyphenols and Human Health: The Role of Bioavailability
- Kawabata et al. (2019): Role of Intestinal Microbiota in the Bioavailability and Physiological Functions of Dietary Polyphenols
- EFSA (2018): Safety of green tea catechins
- European Commission — EU Register of Health Claims
