Polyphenols: Natural Plant Compounds that Combat Inflammation

Once considered little more than decadent indulgences, treats like dark chocolate and red wine have become widely accepted components of a healthy diet in recent years. A big reason why is due to their polyphenols.

These popular ingredients have enjoyed an onslaught of positive publicity lately due to their purported health benefits, with some research claiming that drinking a glass of red wine with dinner or enjoying a few squares of dark chocolate each day can do everything from improve heart health to extend longevity.

Many of these health benefits are due to their content of polyphenols, a type of natural plant compound with powerful antioxidant properties. (Tannins in wine also provide a host of benefits.)

So how can polyphenols affect your health and reduce your risk of chronic disease?

Keep on reading for polyphenols food sources and bioavailability, plus how you can increase your intake to take advantage of the unique health benefits that this micronutrient has to offer.

What are polyphenols?

So what are polyphenols, and how exactly can they affect your health?

The official polyphenols definition is any compound that contains one or more phenolic hydroxyl group, but what does that actually mean?

To put it simply, polyphenols are micronutrients that contain health-promoting properties and can be found in a wide variety of fruits and vegetables.

Plant polyphenols are rich in antioxidants, which can help fight off harmful free radicals and prevent damage to cells while lowering the risk of chronic disease.

Polyphenols have also been associated with many other health benefits, ranging from better blood sugar control to reduced blood clot formation.

Types

There are four groups of polyphenols that are found in different food sources. These main types include:

• Flavonoids — Flavonoids like quercetin, anthocyanins, catechins and kaempferol make up more than 60 percent of polyphenols. They’re in foods like red cabbage, apples, dark chocolate and onions.
• Stilbenes — These natural phenolic include things like the the phytoalexins resveratrol and piceatannol. The skin of grapes, peanuts and red wine host stilbenes.
• Lignans — Lignans are another type of polyphenolic compound and are found in seeds, legumes, whole grains, nuts, fruits and vegetables.
• Phenolic acids — About 30 percent of polyphenols are phenolic acids, which are compounds that come from benzoic and cinnamic acids. Fruits and vegetables have them in their seeds, skins and leaves.

The best way to get in your daily dose of polyphenols is by incorporating plenty of foods with polyphenols into your diet.

Polyphenols supplements are also available but have been associated with some adverse side effects, such as impaired hormone production and increased cancer growth.

Best polyphenols foods

There are plenty of polyphenols food sources available that you can easily add into your diet. In particular, there are a high amount of polyphenols in coffee, berries, cocoa powder, and certain spices and seasonings, like cloves and star anise.

Here are a few of the top polyphenol foods that you may want to consider upping your intake of:

1. Fruits

• Blackberries
• Blueberries
• Strawberries
• Plums
• Apples
• Black currants
• Pomegranates
• Black chokeberries
• Apricots
• Black elderberries
• Raspberries
• Grapes
• Pears
• Peaches
• Nectarines
• Lemon
• Grapefruit
• Cherries

2. Vegetables

• Artichokes
• Spinach
• Red onions
• Chicory
• Asparagus
• Shallots
• Broccoli
• Red lettuce
• Carrots
• Endives
• Potatoes
• Kale
• Cauliflower
• Red cabbage

3. Legumes

• Black beans
• White beans
• Tempeh
• Soy yogurt
• Tofu
• Soy milk
• Soybean sprouts
• Soy “meat”
• Lentils

4. Nuts and seeds

• Hazelnuts
• Walnuts
• Almonds
• Pecans
• Chestnuts
• Flaxseeds
• Pumpkin seeds
• Chia seeds

5. Beverages

• Black tea
• Rooibos tea
• Green tea
• Yerba mate
• Red wine
• Coffee
• Peppermint tea

6. Grains

• Whole wheat
• Wheat bran
• Barley
• Rye
• Oats

7. Herbs and spices

• Basil
• Turmeric
• Marjoram
• Thyme
• Oregano
• Star anise
• Parsley
• Sage
• Peppermint
• Rosemary
• Spearmint
• Lemon verbena
• Caraway
• Celery seed
• Cinnamon
• Cloves
• Cumin
• Ginger
• Curry powder

8. Other foods

• Cocoa powder
• Dark chocolate
• Olive oil
• Capers
• Olives
• Vinegar
• Rapeseed oil

Health benefits

1. High in antioxidants

One of the main benefits of polyphenols is that they’re loaded with powerful antioxidants that can help neutralize free radicals and fight disease.

Free radicals are unstable compounds that form as a result of factors like stress, pollution and an unhealthy diet, building up in the body and causing damage to your cells.

Studies have shown that antioxidants may be protective against a wide variety of conditions, ranging from heart disease to cancer and diabetes. Thanks to the antioxidant content of polyphenols, eating more polyphenols foods may help prevent chronic disease and minimize the risk of oxidative stress.

2. Protect against heart disease

Heart disease is a major concern that affects millions of people around the world. Although there are many potential factors that can play a role in the development of heart disease, switching up your diet to include more polyphenols foods can be an effective way to keep your heart healthy and strong.

Several studies have found that a higher intake of polyphenols is associated with a reduced risk of heart disease.

One human study in the American Journal of Clinical Nutrition showed that those with the highest intake of flavonoids, one particular type of polyphenol, had 18 percent fewer deaths from heart disease compared to those with the lowest intake of flavonoids.

Other research has suggested that polyphenols may reduce the risk of heart disease thanks to their ability to scavenge free radicals and alleviate chronic inflammation.

3. Help relieve inflammation

While acute inflammation is a normal immune response that helps protect against injury and infection, sustaining chronic inflammation for long periods of time can wreak havoc on the body. Not only can it trigger your immune system to begin attacking healthy cells, but it has also been linked to an increased risk of chronic conditions like heart disease, cancer and diabetes.

Polyphenols work by reducing the oxidative stress that contributes to inflammation. Besides having far-reaching effects when it comes to disease prevention, the anti-inflammatory properties of polyphenols may also help reduce symptoms of inflammatory conditions like rheumatoid arthritis, lupus and inflammatory bowel disease.

Further, a 2023 study out of Denmark found that when polyphenols were combined with proteins from foods, specifically adding milk to coffee, it provided enhanced anti-inflammatory effects.

4. May prevent blood clotting

Blood clots can be a serious health concern for many people. They are formed through a process called platelet aggregation, which occurs when the platelets in your blood begin to clump together.

Although this process is necessary to prevent excess bleeding, it can also cause some serious health issues, like stroke, pulmonary embolism and deep vein thrombosis.

Polyphenols may help prevent platelet aggregation to block the formation of blood clots.

Resveratrol, in particular, is one of the most extensively studied polyphenols found primarily in the skins of berries as well as red wine. Both animal models and in vitro studies have demonstrated that resveratrol can effectively inhibit platelet aggregation, reducing the risk of blood clots.

5. May reduce cancer development

In addition to the multitude of beneficial effects on heart health, promising research has indicated that polyphenols may help block the growth of cancer cells as well.

According to a review published in the journal Nutrients, specific types of polyphenols, such as anthoncyanins, flavanols, flavanones and phenolic acids, have been shown to decrease cancer cell growth and development in in vitro studies.

Plus, many of the top cancer-fighting foods also happen to be rich in polyphenols and antioxidants, giving you all the more reason to enjoy plenty of nutrient-dense foods like berries, citrus fruits, leafy green vegetables, and fresh herbs and spices.

6. Support blood sugar control

High blood sugar can result in side effects like frequent urination, fatigue and unintentional weight loss. Left uncontrolled, high blood sugar can also cause a slew of negative effects on long-term health, including diabetes symptoms like nerve damage, vision loss and impaired wound healing.

Polyphenols may be especially beneficial in maintaining normal blood sugar levels and helping prevent diabetes.

According to a 2016 review out of Australia, in vitro studies have found that consuming dietary polyphenols can stimulate insulin secretion and inhibit certain enzymes that break down starches into simple sugars to prevent spikes in blood sugar levels.

A human study published in the British Journal of Nutrition also showed that a higher intake of polyphenols was associated with a lower risk of type 2 diabetes, and further research noted that polyphenols-rich diets have been associated with a lower risk of developing type 2 diabetes.

7. May aid digestion

Polyphenols can help promote digestion through several mechanisms.

For starters, they can positively influence the composition of gut microbiota by promoting the growth of beneficial bacteria, such as Bifidobacteria and Lactobacilli. These probiotics are known to enhance digestive health by breaking down food, producing short-chain fatty acids and maintaining gut barrier integrity.

Chronic inflammation in the gut can impair digestion as well. Polyphenols exhibit anti-inflammatory properties by inhibiting the production of pro-inflammatory cytokines and reducing oxidative stress, which helps maintain a healthy gut environment.

In addition, polyphenols can influence the activity of digestive enzymes. For instance, they can inhibit enzymes like lipase, amylase and protease, which slows down the digestion of fats, carbohydrates and proteins, leading to improved nutrient absorption and better glycemic control.

They also help strengthen the intestinal barrier by promoting the production of tight junction proteins. A robust intestinal barrier prevents the leakage of harmful substances into the bloodstream, thus supporting overall digestive health.

Finally, polyphenols can influence gut motility, ensuring the smooth passage of food through the digestive tract. This is particularly beneficial in preventing constipation and promoting regular bowel movements.

8. Promote brain health

Research has indicated that polyphenols promote brain health in several aspects.

Polyphenols have strong antioxidant properties that protect brain cells from oxidative stress, which is a major contributor to neurodegenerative diseases. By neutralizing free radicals, polyphenols help preserve the integrity and function of neurons.

In addition, chronic inflammation in the brain is linked to cognitive decline and neurodegenerative diseases. Polyphenols can reduce inflammation by inhibiting the production of pro-inflammatory cytokines and modulating signaling pathways involved in the inflammatory response.

Some polyphenols, such as those found in green tea, have been shown to promote neurogenesis, the process of generating new neurons. This can enhance brain plasticity and improve cognitive functions.

Polyphenols can improve cerebral blood flow by enhancing endothelial function and promoting the production of nitric oxide, which helps dilate blood vessels. Improved blood flow ensures adequate oxygen and nutrient delivery to brain tissues, supporting cognitive health.

Polyphenols can influence the gut microbiota composition, promoting the growth of beneficial bacteria that produce metabolites with neuroprotective effects. These metabolites can cross the blood-brain barrier and exert beneficial effects on the brain.

Polyphenols can protect neurons from damage caused by neurotoxins, such as amyloid-beta plaques and tau tangles, which are associated with Alzheimer’s disease. By preventing the aggregation of these toxic proteins, polyphenols help preserve cognitive function.

Lastly, synaptic plasticity is crucial for learning and memory. Polyphenols can enhance synaptic plasticity by modulating signaling pathways involved in synaptic strength and communication, such as the brain-derived neurotrophic factor pathway.

9. Promote longevity

Considering all the benefits polyphenols have to offer, it should come as no surprise that research published in 2024 revealed that these powerful plant compounds also promote a long, healthy life. In particular, this research shared that polyphenols have anti-aging properties that support longevity, including helping slow brain aging, improve immune health and protect against age-related diseases.

Another study from 2023 relayed similar findings. This study found that following a Mediterranean diet and green Mediterranean diet high in polyphenols foods was inversely associated with biological aging.

These results confirm that foods high in polyphenols should be included in a longevity diet.

Polyphenols in traditional medicine

Many of the ingredients commonly used in Traditional Chinese Medicine and Ayurvedic medicine are rich in polyphenols and have been utilized for their medicinal properties for centuries.

Cloves, for instance, are loaded with polyphenols. In Ayurveda, cloves are believed to promote digestive health, enhance blood flow and boost metabolism.

In Traditional Chinese Medicine, cloves are said to affect the health of the spleen, lungs and kidneys. They are also used to help warm the body and treat conditions like hiccups, abdominal pain and diarrhea.

Green tea, meanwhile, is used in Traditional Chinese Medicine for its cooling properties and is believed to remove heat and phlegm while stimulating digestion, urination and the production of bodily fluids.

Other foods like berries, pomegranates, greens, nuts and herbs are similarly rich in polyphenols and utilized in Ayurveda and Traditional Chinese Medicine to promote better health and help ward off illness and infections.

In recent years, red wine has garnered a huge amount of attention for its purported health benefits.

A phenomenon known as the French Paradox was initially described in the 1980s, when researchers noted that French people had lower rates of coronary heart disease than other countries despite higher intakes of saturated fat and regular consumption of red wine.

There are many potential explanations and theories for the French Paradox, but it’s believed to partially stem from the polyphenol content of red wine.

Resveratrol, one of the most well-known types of polyphenols, is plentiful in red wine as well as the skin of certain types of berries, like grapes, blueberries and raspberries. First isolated in 1939 by a Japanese researcher, resveratrol has since been associated with a number of important health benefits.

It’s been shown to lower biomarkers for specific diseases and could even be therapeutic for conditions like neurological disorders, heart disease and diabetes.

Today, numerous types of polyphenols have been identified and shown to have powerful effects on health. From hesperidin found in citrus fruits like lemons and oranges to epigallocatechin gallate (EGCG) in green tea, there are many different types of polyphenols available in the diet that all boast a unique set of health benefits.

Risks and side effects

Lectins are a type of protein found in a wide array of foods, such as beans, wheat and potatoes. In small amounts, lectins can actually come with some pretty impressive health benefits.

In larger quantities, however, they can disrupt digestion and even damage the lining of the intestines.

Much like polyphenols, lectins are a type of antinutrient, meaning that they can impair absorption of certain vitamins and minerals.

In vitro studies show that polyphenols may block the absorption of iron in a dose-dependent manner.

Lectins, on the other hand, inhibit absorption of a wider range of micronutrients and can even cause gastrointestinal upset with symptoms like indigestion, gas and bloating.

If lectins cause issues for you, there are several ways to reduce the lectin content in polyphenol-rich foods.

Soaking beans and legumes, for instance, has been shown to slash lectin content in half. Sprouting these foods can also be beneficial, allowing you to take advantage of the unique health benefits of polyphenols while minimizing the amount of lectins in your diet.

Although loading up on the polyphenols foods is unlikely to cause any negative side effects, capsules and supplements have been associated with some potential adverse health effects.

Polyphenol supplementation may actually have carcinogenic effects and can even disrupt the production of thyroid hormones as well. It can also interfere with certain medications and could impair iron absorption as well.

Ideally, it’s best to stick to dietary sources of polyphenols instead of using supplementation. Besides containing a hearty dose of polyphenols and antioxidants, these highly nutritious foods can also provide a host of other valuable vitamins, minerals and micronutrients.

If you do decide to take a polyphenol supplement, however, you may want to consult with your doctor if you have a history of thyroid problems, iron deficiency or cancer, or if you’re taking anti-diabetes medications or blood thinners to prevent an interaction.

If you have any other health concerns or experience any adverse side effects as a result of taking polyphenol supplements, you should also consider consulting with a healthcare practitioner to determine the best course of action.

Final thoughts

• Polyphenols are a type of plant compound and micronutrient found in many different fruits and vegetables.
• They are high in antioxidants and have been associated with improved heart health, better blood sugar control, reduced inflammation and a reduced risk of cancer development.
• Some of the best sources of polyphenols include fruits, vegetables, nuts, beans, tea, coffee, herbs and spices.
• Although polyphenol supplements are also available, it’s best to increase your intake of polyphenol foods instead to minimize the risk of adverse side effects.
• Combine polyphenol-rich foods with a balanced diet and healthy lifestyle to maximize the potential benefits and reduce your risk of chronic disease.