Polyphenols are a category of compounds naturally found in plant foods, such as fruits, vegetables, herbs, spices, tea, dark chocolate, and wine.

They can act as antioxidants, meaning they can neutralize harmful free radicals that would otherwise damage your cells and increase your risk of conditions like cancer, diabetes, and heart disease (1Trusted Source).

Polyphenols are also thought to reduce inflammation, which is thought to be the root cause of many chronic illnesses (2Trusted Source, 3Trusted Source).

Types of polyphenols

More than 8,000 types of polyphenols have been identified. They can be further categorized into 4 main groups (4Trusted Source, 5Trusted Source):

• Flavonoids. These account for around 60% of all polyphenols. Examples include quercetin, kaempferol, catechins, and anthocyanins, which are found in foods like apples, onions, dark chocolate, and red cabbage.
• Phenolic acids. This group accounts for around 30% of all polyphenols. Examples include stilbenes and lignans, which are mostly found in fruits, vegetables, whole grains, and seeds.
• Polyphenolic amides. This category includes capsaicinoids in chili peppers and avenanthramides in oats.
• Other polyphenols. This group includes resveratrol in red wine, ellagic acid in berries, curcumin in turmeric, and lignans in flax seeds, sesame seeds, and whole grains.

The amount and type of polyphenols in foods depend on the food, including its origin, ripeness, and how it was farmed, transported, stored, and prepared.

Polyphenol-containing supplements are available as well. However, they’re likely to be less beneficial than polyphenol-rich foods (6Trusted Source).

Summary

Polyphenols are beneficial plant compounds with antioxidant properties that may help keep you healthy and protect against various diseases. They can be subdivided into flavonoids, phenolic acid, polyphenolic amides, and other polyphenols.

Polyphenols have been linked to various health benefits.

May lower blood sugar levels

Polyphenols may help lower your blood sugar levels, contributing to a lower risk of type 2 diabetes.

That’s partly because polyphenols may prevent the breakdown of starch into simple sugars, lowering the likelihood of blood sugar spikes after meals (7Trusted Source).

These compounds may also help stimulate the secretion of insulin, a hormone that’s required to shuttle sugar from your bloodstream into your cells and keep your blood sugar levels stable (7Trusted Source).

Various studies further link polyphenol-rich diets to lower fasting blood sugar levels, higher glucose tolerance, and increased insulin sensitivity — all important factors in lowering your risk of type 2 diabetes (8Trusted Source).

In one study, people eating the highest amounts of polyphenol-rich foods had up to a 57% lower risk of developing type 2 diabetes over 2–4 years, compared with those eating the lowest amounts (9Trusted Source).

Among polyphenols, research suggests that anthocyanins may offer the most potent antidiabetic effect. They’re typically found in red, purple, and blue foods, such as berries, currants, and grapes (10Trusted Source, 11Trusted Source).

May lower your risk of heart disease

Adding polyphenols to your diet may improve heart health.

Experts believe that this is largely due to the antioxidant properties of polyphenols, which help reduce chronic inflammation, a risk factor for heart disease (3Trusted Source, 12Trusted Source, 13Trusted Source).

Two recent reviews link polyphenol supplements to lower blood pressure and LDL (bad) cholesterol levels, as well as higher HDL (good) cholesterol (14Trusted Source, 15Trusted Source).

Another review found a 45% lower risk of death from heart disease in those with higher enterolactone levels, which are a marker of lignan intake. Lignans are a type of polyphenol typically found in flax seeds and whole grains (16Trusted Source).

May prevent blood clots

Polyphenols may reduce your risk of developing a blood clot.

Blood clots are formed when platelets circulating in your bloodstream begin to clump together. This process is known as platelet aggregation and is useful in preventing excess bleeding.

However, excess platelet aggregation can cause blood clots, which can have negative health effects, including deep vein thrombosis, stroke, and pulmonary embolism (17Trusted Source).

According to test-tube and animal studies, polyphenols may help reduce the platelet aggregation process, thereby preventing the formation of blood clots (18Trusted Source, 19Trusted Source, 20Trusted Source).

May protect against cancer

Research consistently links diets rich in plant foods to a lower risk of cancer, and many experts believe that polyphenols are partly responsible for this (5Trusted Source, 21, 22Trusted Source).

Polyphenols have strong antioxidant and anti-inflammatory effects, both of which can be beneficial for cancer prevention (23).

A recent review of test-tube studies suggests that polyphenols may block the growth and development of various cancer cells (5Trusted Source, 24Trusted Source).

In humans, some studies link high blood markers of polyphenol intake to a lower risk of breast and prostate cancers, while others find no effects. Therefore, more studies are needed before strong conclusions can be made (25Trusted Source).

May promote healthy digestion

Polyphenols may benefit digestion by promoting the growth of beneficial gut bacteria while fending off harmful ones (26Trusted Source, 27Trusted Source).

For instance, evidence suggests that polyphenol-rich tea extracts can promote the growth of beneficial bifidobacteria (28Trusted Source).

Similarly, green tea polyphenols may help fight off harmful bacteria, including C. difficile, E. Coli, and Salmonella,as well as improve symptoms of peptic ulcer disease (PUD) and inflammatory bowel disease (IBD) (29Trusted Source, 30Trusted Source).

Furthermore, emerging evidence indicates that polyphenols may help probiotics thrive and survive. These are beneficial bacteria that occur in certain fermented foods and can be taken in supplement form. However, more research is needed (31Trusted Source).

May promote brain function

Polyphenol-rich foods may boost your focus and memory.

One study reports that drinking grape juice, which is naturally rich in polyphenols, helped significantly boost memory in older adults with mild mental impairment in as little as 12 weeks (32Trusted Source).

Others suggest that cocoa flavanols may improve blood flow to the brain and have linked these polyphenols to improved working memory and attention (33Trusted Source, 34Trusted Source, 35Trusted Source, 36Trusted Source).

Similarly, the polyphenol-rich plant extract Ginkgo biloba appears to boost memory, learning, and concentration. It has also been linked to improved brain activity and short-term memory in those with dementia (37Trusted Source).

Summary

Polyphenols may help prevent blood clots, reduce blood sugar levels, and lower heart disease risk. They may also promote brain function, improve digestion, and offer some protection against cancer, though more research is needed.

Though tea, dark chocolate, red wine, and berries are likely the best-known sources of polyphenols, many other foods also contain high amounts of these beneficial compounds.

Here are the 75 foods richest in polyphenols, listed by category (38Trusted Source).

Fruits

• apples
• apricots
• black chokeberries
• black and red currants
• black elderberries
• black grapes
• blackberries
• blueberries
• cherries
• grapes
• grapefruit
• lemon
• nectarines
• peaches
• pears
• pomegranate
• plums
• raspberries
• strawberries

Vegetables

• artichokes
• asparagus
• broccoli
• carrots
• endives
• potatoes
• red chicory
• red lettuce
• red and yellow onions
• spinach
• shallots

Legumes

• black beans
• tempeh
• tofu
• soybean sprouts
• soy meat
• soy milk
• soy yogurt
• white beans

Nuts and seeds

• almonds
• chestnuts
• hazelnuts
• flax seeds
• pecans
• walnuts

Grains

• oats
• rye
• whole wheat

Herbs and spices

• caraway
• celery seed
• cinnamon
• cloves
• cumin
• curry powder
• dried basil
• dried marjoram
• dried parsley
• dried peppermint
• dried spearmint
• lemon verbena
• Mexican oregano
• rosemary
• sage
• star anise
• thyme

Other

• black tea
• capers
• cocoa powder
• coffee
• dark chocolate
• ginger
• green tea
• olives and olive oil
• rapeseed oil
• red wine
• vinegar

Including foods from each of these categories in your diet provides you a wide variety of polyphenols.

Summary

Many plant foods are naturally rich in polyphenols. Including a variety of these foods in your diet is a great strategy to boost your intake of these beneficial nutrients.

Supplements have the advantage of offering a consistent dose of polyphenols. However, they also have several potential drawbacks.

First, supplements haven’t been consistently shown to offer the same benefits as polyphenol-rich foods, and they don’t contain any of the additional beneficial plant compounds typically found in whole foods.

Moreover, polyphenols seem to work best when interacting with the many other nutrients naturally found in foods. It’s currently unclear whether isolated polyphenols, such as those in supplements, are as effective as those found in foods (6Trusted Source, 39Trusted Source).

Finally, polyphenol supplements aren’t regulated, and many contain doses over 100 times larger than those in foods. More research is needed to establish safe and effective dosages, and it’s unclear whether these large doses are beneficial (39Trusted Source, 40Trusted Source).

Summary

Polyphenol supplements may not offer the same health benefits as polyphenol-rich foods. Effective and safe dosages haven’t been determined.

Polyphenol-rich foods are safe for most people.

The same cannot be said of supplements, which tend to provide much higher quantities of polyphenols than those typically found in a healthy diet (39Trusted Source).

Animal studies show that high-dose polyphenol supplements may cause kidney damage, tumors, and an imbalance in thyroid hormone levels. In humans, they may result in an increased risk of stroke and premature death (39Trusted Source, 40Trusted Source).

Some polyphenol-rich supplements can interact with nutrient absorption or interact with medications. For instance, they may reduce your body’s ability to absorb iron, thiamine, or folate (39Trusted Source, 41Trusted Source, 42Trusted Source).

If you have a diagnosed nutrient deficiency or are taking medications, it may be best to speak to your healthcare provider about polyphenol supplements before taking them.

In addition, some polyphenol-rich foods, such as beans and peas, may be rich in lectins. When consumed in large quantities, lectins may cause unpleasant digestive symptoms, such as gas, bloating, and indigestion (43Trusted Source).

If this is an issue for you, try soaking or sprouting your legumes before eating them, as this can help reduce the lectin content by up to 50% (44Trusted Source, 45Trusted Source).

Summary

Polyphenol-rich foods are considered safe for most people, while supplements may cause more harm than good. To reduce gas, bloating, and indigestion, try soaking or sprouting polyphenol-rich legumes before eating them.

Polyphenols are beneficial compounds in many plant foods that can be grouped into flavonoids, phenolic acid, polyphenolic amides, and other polyphenols.

They may improve digestion, brain function, and blood sugar levels, as well as protect against blood clots, heart disease, and certain cancers.

More research is needed to identify effective and safe polyphenol supplement dosages.

Therefore, for the time being, it’s best to rely on foods rather than supplements to boost your intake of these healthful compounds.

A number of different types of berries are rich in polyphenols. These include popular and easily accessible berries like:

• highbush blueberries, with 560 mg polyphenols
• blackberries, with 260 mg polyphenols
• strawberries, with 235 mg polyphenols
• red raspberries, with 215 mg polyphenols

The berry with the most polyphenols? Black chokeberry, which has more than 1,700 mg polyphenolsTrusted Source per 100 g.

Berries aren’t the only fruits with plenty of polyphenols. According to the American Journal of Clinical Nutrition, a large number of fruits contain high numbers of polyphenols. These include:

• black currants, with 758 mg polyphenols
• plums, with 377 mg polyphenols
• sweet cherries, with 274 mg polyphenols
• apples, with 136 mg polyphenols

Fruit juices like apple juice and pomegranate juice also contain high numbers of this micronutrient.

Beans contain a large number of nutritional benefits, so it’s no surprise that they naturally have hefty doses of polyphenols. Black beans and white beans in particular have the highest number of polyphenolsTrusted Source. Black beans have 59 mg per 100 g, and white beans have 51 mg.

Shop for beans here.

Nuts can be high in caloric value, but they pack a powerful nutritional punch. Not only are they full of protein; some nuts also have high polyphenol content.

One 2012 studyTrusted Source found significant levels of polyphenols in a number of both raw and roasted nuts. Nuts high in polyphenols include:

• hazelnuts, with 495 mg polyphenols
• walnuts, with 28 mg polyphenols
• almonds, with 187 mg polyphenols
• pecans, with 493 mg polyphenols

Purchase nuts online.

There are many vegetables that contain polyphenols, though they usually have less than fruit. Vegetables with high numbers of polyphenols include:

• artichokes, with 260 mg polyphenols
• chicory, with 166–235 mg polyphenols
• red onions, with 168 mg polyphenols
• spinach, with 119 mg polyphenols

Soy, in all its various forms and stages, contains large numbersTrusted Source of this valuable micronutrient. These forms include:

• soy tempeh, with 148 mg polyphenols
• soy flour, with 466 mg polyphenols
• tofu, with 42 mg polyphenols
• soy yogurt, with 84 mg polyphenols
• soybean sprouts, with 15 mg polyphenols

Purchase soy flour here.

Want to shake it up? In addition to high-fiber fruits, nuts, and vegetables, black and green teasTrusted Source both contain ample amounts of polyphenols. Black tea clocks in with 102 mg polyphenols per 100 milliliters (mL), and green tea has 89 mg.

Find black teas and green teas online.

Many people drink a glass of red wine every night for the antioxidants. The high number of polyphenolsTrusted Source in red wine contributes to that antioxidant count. Red wine has a total of 101 mg polyphenols per 100 mL.

Rosé and white wine, while not as beneficial, still have a decent chunk of polyphenols, with 100 mL of each having about 10 mg polyphenols.

There are some risks and complications associated with polyphenols. These seem to be most heavily associated with taking polyphenol supplements. More research is needed to evaluate the actual risk of these complications, which include:

• carcinogenic effects
• genotoxicity
• thyroid issues
• estrogenic activity in isoflavones
• interactions with other prescription medications

Polyphenols are powerful plant compounds that our body needs. They have numerous health benefits that may offer protection from the development of cancers, cardiovascular disease, osteoporosis, and diabetes.

It’s best to consume polyphenols through foods naturally containing them, instead of through artificially made supplements, which may come with more side effects. If you take supplements, make sure they are made from a reputable company with high quality sourcing.