What are polyphenols?
Polyphenols are plant compounds that have powerful antioxidant properties. Polyphenols protect us against chronic diseases.
There are over 8000 polyphenols identified in nature, acting as antioxidants.
Polyphenols are phytochemicals that give the food its color, flavor, or bitterness.
Polyphenols protect plants from oxidation. Additionally, they protect the human body from free radical damage and against UV radiation.
Several epidemiological studies strongly showed that the consumption of polyphenols offered better protection against chronic diseases such as:
- cardiovascular diseases,
- neurodegenerative diseases, and
Recommended Daily Intake of Polyphenols
Polyphenols don’t have an officially approved daily intake recommended value, like vitamins and minerals.
Polyphenols don’t store in the body, so any health effect is difficult to be measured.
Also, it isn’t always easy to measure the bioavailability of polyphenols.
Most noteworthy, scientists try to find out the daily amounts of polyphenols that we should consume for best health benefits (4).
Many studies have been conducted to find the daily polyphenol consumption of the population around the globe.
For instance, scientists measured that the daily intake of polyphenols was between 183–4854 mg per day in Japan (5).
On the contrary, in the famous EPIC study, scientists measured that the daily intake of polyphenols was 584–1786 mg per day (6).
The EPIC study is a well known large study conducted in 10 European countries: Denmark, France, Germany, Greece, Italy, Norway, Spain, Sweden, The Netherlands, and the UK. Scientists tried to investigate the role of diet, and other environmental factors on the etiology of cancer, and other chronic diseases. Over half a million participants were recruited (6).
The highest total polyphenol intake was in Denmark (1,786 mg per day), whereas the lowest intake was in Greece (584 mg per day) (6).
Studies have found that the daily polyphenol intake is on average 1000 mg, depending on lifestyle and dietary preferences (11). Other studies suggest daily polyphenol intake higher than 500 mg, for greater health benefits (9).
According to all these, a good goal is to aim to get at least 1000 milligrams of polyphenols a day, though this limit it’s totally arbitrary.
High consumption of polyphenols is highly unlikely to cause toxicity (7). Therefore, you should increase the daily consumption of foods rich in polyphenols.
Practically… Follow a plant-based diet. Plants are the only foods rich in polyphenols.
Types of Polyphenols
Polyphenols are divided into four different categories (1):
- Flavonoids are predominantly in fruits, vegetables, legumes, red wine, and green tea. They are further divided into flavones, flavonols, flavanones, isoflavones, anthocyanidins, chalcones, and catechins. They have potential health benefits as complementary medicine and utilized in various formulation implied for antioxidant, anti-inflammatory, neuroprotective, anti-diabetic, anticancer, anti-infertility, anti-obesity, anti-arthritic, neuroprotective, antihyperlipidemic, anti-cataract and wound healing properties (1).
- Stilbenes are found in red wine and peanuts. The most well-known compound of this group is resveratrol.
- Phenolic acids are found in coffee, tea, cinnamon, blueberries, kiwis, plums, apples, and cherries.
- Lignans are found in seeds. Flaxseed is especially rich in lignans. Legumes, whole-cereals, whole-grains, fruits, algae, and certain vegetables are all good sources as well.
Food usually contains complex polyphenols, mainly found in the outer layers of the plants. Avoid throwing away the peel of fruits and vegetables. Prefer organic foods, as pesticides tend to accumulate in the peel.
Health benefits of Polyphenols
Polyphenols protect plants from:
- UV radiation,
- oxidative stress, and
- harsh climatic conditions.
Furthermore, polyphenols are so important for the human body. They can prevent several major chronic diseases associated with oxidative stress, having many powerful biological properties such as (1,2,8,9):
- cerebrovascular protection,
- antibacterial and
- antiviral properties
Start consuming foods rich in polyphenol today…
What foods are high in polyphenols?
Plants are the only good sources of polyphenols.
Fruits, vegetables, legumes, whole-cereals, even chocolate, tea, and coffee are all good sources of polyphenols.
For instance, the average 100 grams of fruits (such as grapes, apple, pear, cherries, and berries) contains up to 300 mg of polyphenols.
The European Journal of Clinical Nutrition published the 100 richest dietary sources of polyphenols (2).
To better understand the polyphenol sources, scientists compared food groups:
- seasoning group found to be the most important, as contained the highest number of foods rich in polyphenols per weight (mg per 100 g). It contained 22 out of the 100 richest foods in polyphenol.
- fruit group is second with 20 foods.
- seeds with 16 foods,
- vegetables with 16 foods,
- non-alcoholic beverages with 11 foods,
- cereals with 10 foods,
- cocoa products with 4 foods,
- alcoholic beverages with 3 foods, and
- oils with only 2 foods.
The polyphenol contents ranged from more than 15000 mg per 100 g in cloves to 7.8 mg per 100 ml in rosé wine (2).
The richest sources of polyphenols are spices and herbs.
The richest food in polyphenols is cloves. By far…
Other herbs contain high amounts of flavanones (a type of polyphenol), as well. The best sources are peppermint, Mexican oregano, sage, rosemary, spearmint, and thyme.
Certainly, we can’t consume large amounts of spices and herbs. Therefore, it is more practical to estimate the amounts of polyphenols per serving.
List of common foods rich in polyphenols
Berries are rich in polyphenols
Berries are also good sources of polyphenols. The main polyphenol type they contain is anthocyanins.
Black chokeberry, black elderberry, blueberry, and blackcurrant are all rich in polyphenols.
As you can see, they all have dark color. The darker the better. Antioxidants are the colored pigments of foods.
As a rule of thumb, colored or dark fruits and vegetables are richer in polyphenols & other antioxidants.
Fruits rich in polyphenols
Plum, cherry, and blackberry are the richest sources of polyphenols among the fruit group. Don’t forget, they’re the darkest ones…
Other fruits rich in polyphenols are strawberries, raspberries, grapes, apples, peaches, apricots, nectarines, and pears.
Seeds and nuts rich in polyphenols
Flaxseed is especially rich in lignan (a type of polyphenol).
Chestnut, walnut, hazelnut, pecan nut, almond are other nuts rich in polyphenols.
Soy flour and roasted soybean are rich in isoflavones (a type of polyphenol).
Cocoa powder and chocolate are also rich in polyphenols.
Vegetables rich in polyphenols
The richest vegetable sources of polyphenols are black and green olives, which are particularly rich in tyrosols.
Beverages rich in polyphenols
Good news everyone…
The richest beverage in polyphenols is coffee. Black tea, green tea, and red wine are also beverages rich in polyphenols.
Typically, a cup of tea or coffee or a glass of red wine contains more than 100 mg of polyphenols. Thereby tea, coffee, and red wine may protect us from chronic diseases (1).
A study showed that coffee and green tea are the major sources of polyphenols (5). 43% of the polyphenols came from coffee. 26% came from green tea.
Some fruit juices also contain great amounts of polyphenols. For instance, pomegranate juice is particularly rich in polyphenols and other antioxidants.
Other common foods rich in polyphenols
Furthermore, cereals, such as whole grain flours from wheat or rye contain polyphenols.
Last, but not least two vegetable oils contain polyphenols.
The second vegetable oil rich in polyphenols is the rapeseed oil.
The detailed table of the 100 polyphenol-richest foods is here.
Serving size matters
Certain foods and beverages, such as beer, doesn’t appear among the 100 top polyphenol-richest foods. Due to the fact that the typical serving size is much greater, they may contribute to the total polyphenol intake.
Such foods, that highly contribute to the daily polyphenol intake, although they aren’t particularly rich in polyphenol per 100 gr, are fruits, globe artichoke heads, coffee, black tea, green tea, and red wine.
On the contrary, dark chocolate and cocoa powder, although they are rich in polyphenols, they don’t contribute as much in the daily polyphenol intake.
Prefer the dark chocolate of 85% cocoa. It contains fiber, many minerals, especially iron, and of course, polyphenols.
The consumption of cocoa, tea or coffee could easily increase the daily polyphenol intake by 500–1000 mg (7). Good news…
Enhance bioavailability of polyphenols
The diversity of polyphenols makes it difficult to estimate the total polyphenol content of foods.
It is still important to highlight that polyphenol losses due to cooking and food processing can have a great impact on the intake of some polyphenols. For instance, cooking may destroy unique polyphenols in onions (6).
Peeling also removes many polyphenols. For example, red wine is produced from polyphenol-rich grape skins, resulting in a polyphenol content 10 times greater than white wine.
Moreover, processed food may contain different amounts of polyphenols than the original food (7).
10 practical daily advises
- Don’t remove the peel of fruits and vegetables.
- Prefer organic foods, as pesticides tend to accumulate in the peel.
- Raw or unprocessed foods are higher in polyphenols.
- Coffee, cocoa, and green tea can enhance your polyphenol daily intake.
- Consume whole-grains and cereals.
- Experiment with cloves in recipes.
- Use herbs and spices.
- Eat lots of seeds and nuts.
- Eat dark colored fruits and berries.
- Use extra virgin olive oil.
- NCBI – PMC: A Critical Review on Polyphenols and Health Benefits of Black Soybeans
- Nature.com – European Journal of Clinical Nutrition: Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database
- Office of Disease Prevention and Health Promotion (ODPHP): Dietary Guidance for Americans 2015-2020
- NCBI – PMC: The role of polyphenols in modern nutrition
- NCBI – PMC: Estimated Dietary Polyphenol Intake and Major Food and Beverage Sources among Elderly Japanese
- NCBI – PMC: Dietary polyphenol intake in Europe: the European Prospective Investigation into Cancer and Nutrition (EPIC) study
- British Journal of Nutrition: Dietary reference intake (DRI) value for dietary polyphenols: are we heading in the right direction?
- NCBI – PMC: Effects of Polyphenol-Rich Foods on Human Health
- NCBI – PMC: Systematic Review on Polyphenol Intake and Health Outcomes: Is there Sufficient Evidence to Define a Health-Promoting Polyphenol-Rich Dietary Pattern?
- Oxford Academic – The Journal of Nutrition: Dietary Intake and Bioavailability of Polyphenols
- NCBI– PMC: Tea polyphenols, their biological effects and potential molecular targets