Polyphenols are plant compounds that are largely beneficial to your health. They’re naturally found in plant-based foods like fruits, vegetables, herbs, tea, red wine, coffee, and dark chocolate.
Polyphenols act as antioxidants in the body. This means they help protect the body and neutralize free radicals that cause damage to cells.
This article discusses the types of polyphenols, their possible health benefits, and their potential risks.
Types of Polyphenols
Over 8,000 polyphenols have been discovered but researchers are still trying to understand how the chemicals affect the human body.
Flavonoids
Flavonoidsare found in foods like onions, kale, parsley, tea, red wine, and soybeans.They make up over half of the currently known polyphenols.
The six different types of flavonoids are:
- Anthocyanins
- Flavan-3-ols
- Flavones
- Flavanones
- Flavonols
- Isoflavonoids
Flavonoids account for 60% of dietary polyphenols.
Phenolic Acid
Phenolic acid is found in foods like grapes, berries, pomegranates, walnuts, chocolate, coffee, and green tea.
Phenolic acid accounts for about 30% of all known polyphenols. The two classes of phenolic acid are hydroxybenzoic acid and hydroxycinnamic acid.
Polyphenolic Amides
Polyphenolic amides have subgroups called capsaicinoids and avenanthramides. Capsaicinoids are found in chili peppers and create the hotness of the pepper.
Avenanthramides are found in oats and are believed to help with LDL (low-density lipoprotein or “bad”)cholesterol.
Other Polyphenols
Some polyphenols only have one type, and they account for a smaller portion of the compounds. This group includes polyphenols like:
- Resveratrol is unique to grapes and red wine.
- Ellagic acid is found in berry fruits, such as strawberries and raspberries, and the skin of tree nuts.
- Curcumin is a strong antioxidant that gives the spice turmeric its yellow color.
- Lignans are found in flax, sesame, and some other grains.
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Health Benefits of Polyphenols
Most of the health benefits of polyphenols relate to their role as an antioxidant. Antioxidants help protect cells from damage caused by free radicals. Free radicals are highly reactive oxygen molecules produced by normal cell processes, radiation, air pollution, smoking, or chemical exposure.
It’s thought that eating enough antioxidants may help keep your body’s cells healthy and lower your risk for some diseases.
Researchers are still discovering the health benefits of polyphenols, so more research is needed to understand all the benefits this compound could provide. Here are some of the potential health benefits of polyphenols.
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Lower Blood Sugar Levels
Polyphenols may help keep blood sugar levels within a healthy range. One study suggested that regularly consuming tea was associated with a lower risk of developingtype 2 diabetes.
Summaries of medical studies (systematic reviews) and examinations of data from many independent studies (meta-analyses) have suggested that each cup of coffee consumed daily may reduce a person’s risk of developing diabetes by up to 8%.
The anthocyanins found in berries and grapes are another polyphenol associated with lowering the risk of developing and helping to manage type 2 diabetes.
It’s believed that these polyphenols help blood sugar levels by:
- Protecting the insulin-producing cells in the pancreas from oxidation by free radicals
- Reducing inflammation
- Preventing starches and simple carbs from being fully digested, which helps prevent blood sugar spikes
Increase Insulin Sensitivity
One of the potential causes of type 2 diabetes isinsulin resistance. When you become insulin resistant, your body’s cells become less responsive to the hormone insulin. As a result, glucose stays in the bloodstream longer.
Increasing the cells’ sensitivity toinsulinhelps bring more glucose in from the blood and keep blood sugar levels within a healthy range.
One clinical trial looked at the effects of adding more than 300 milligrams of polyphenols from strawberries and cranberries to participants’ diets. The researchers found that the polyphenols in strawberries and cranberries effectively increased insulin sensitivity in people with insulin resistance.
Lower Cancer Risk
Plant-based diets are frequently linked to a lower cancer risk and polyphenols are thought to contribute to that reduced risk.
Research has shown that polyphenols may reduce the risk of developing some types ofcancer, such as:
- Colon cancer
- Prostate cancer
- Skin (epithelial) cancer
- Endometrial (lining of the uterus) cancer
- Breastcancer
Since antioxidants help prevent cell damage, it’s believed polyphenols may lower the chances of cells mutating from damage and becoming cancerous. Polyphenols like flavonoids may help control tumor cell growth and signal cell death to remove cancerous cells (apoptoticfactors).
Reduce Inflammation
Chronicinflammationis linked to an increased risk of developing many health conditions, like heart disease, diabetes, cancer, and autoimmune diseases.
One study looked at the effect of polyphenol lignans on inflammatory markers in the body. The study found the higher the concentration of lignans in the body, the lower a person’s markers of inflammation were.
Improve Heart Health
Adding more polyphenols to your diet may improve your heart health and lower your risk of cardiovascular diseases.Polyphenols may improve multiple risk factors for heart disease, including:
- Lower blood pressure
- Lower LDL ("bad) cholesterol
- Raise HDL ("good") cholesterol
- May prevent blood clots
Resveratrol, lignans, and flavonoids have all been linked to lower heart disease risk. However, it is worth noting that not all studies have shown these benefits. For example, resveratrol has not always been shown to have heart-health benefits. That could be because red wine is usually consumed in smaller amounts than other antioxidant-rich foods and drinks since it contains alcohol.
Boost Brain Function
Some studies have suggested that polyphenols may boost brain function and protect against neurodegenerative diseases likeAlzheimer’s disease.
For example, some research suggests that curcumin, a powerful polyphenol found in turmeric, can have an effect on neurodegenerative (brain) diseases like Alzheimer’s. However, more study is needed.
Another study found that older adults who drank green tea were less likely to experience cognitive decline than people who drank coffee or black tea.
The benefits for brain function could be related to the antioxidant effects and improvements in blood flow to the brain.
Improve Digestion
Polyphenols may improve your digestion by promoting the growth of beneficial bacteria in your GI tract while limiting the growth of harmful ones.
For example, studies have suggested that blueberries may promote the growth of the “good” bacterium bifidobacteria. Green tea may slow the growth of potentially harmful bacteria likeClostridioides difficile(C. diff),Escherichia coli(E. coli), andSalmonella typhimurium.
The microbiome is the balance of microbes normally present in the digestive tract. Researchers are just starting to understand thegut microbiome’srole in overall health. It’s believed the bacteria in the gut play a role in mental health, the immune system, digestion, and more. So, maintaining a healthy balance of good bacteria is thought to support your overall health.
Polyphenol-Rich Foods
Polyphenols are found in a variety of plant-based foods. Usually, people have heard of the antioxidants in popular foods like dark chocolate, tea, red wine, coffee, and berries. You may not know polyphenols are also in many other common foods, including:
Vegetables
Vegetables high in polyphenols include:
- Broccoli
- Carrots
- Spinach
- Red lettuce
- Onions
- Asparagus
- Artichokes
- Shallots
- Garlic
Fruits
Fruits high in polyphenols include:
- Blueberries
- Strawberries
- Raspberries
- Blackberries
- Cranberries
- Grapes
- Cherries
- Lemon
- Grapefruit
- Oranges
- Pears
- Apples
- Peaches
- Plums
- Pomegranate
- Nectarine
- Apricots
- Olives and olive oil
Grains
Grains high in polyphenols include:
- Oats
- Rye
- Wheat
Nuts and Seeds
Nuts and seeds high in polyphenols include:
- Walnuts
- Almonds
- Flaxseed
- Chia seeds
- Pecans
- Chestnuts
- Hazelnuts
Legumes
Legumes high in polyphenols include:
- Black beans
- White beans
- Soybeans
- Tofu
- Tempeh(made from fermented soybeans)
Herbs and Spices
Herbs and spices high in polyphenols include:
- Turmeric
- Cinnamon
- Cumin
- Cloves
- Celery seed
- Basil
- Ginger
- Marjoram
- Parsley
- Peppermint
- Oregano
- Rosemary
- Sage
- Thyme
- Lemon verbena
Other
Other foods and drinks high in polyphenols include:
- Green tea
- Black tea
- Red wine
- Dark chocolate
- Cocoa powder
- Coffee
- Vinegar (especially fruit or wine vinegars)
Risks and Side Effects
Eating a balance of polyphenol-rich foods is safe for most people.
However, if you’re considering trying a polyphenol supplement, understand that there could be potential side effects. Supplements are not regulated by the Food and Drug Administration (FDA) and they tend to deliver higher doses of polyphenols than what you would get from food.
More research is needed to understand the safety and effectiveness of polyphenol supplements. Be sure to talk with your healthcare provider before taking any new supplements.
Many polyphenol-rich foods are high in other compounds, like fiber.Suddenly increasing your fiber intakecan lead to some digestive discomfort, like gas, bloating, and constipation.If you’re looking to increase the number of polyphenols in your diet, try adding more slowly.
Lectin is another component of plant-based foods. Some food sources that are high in these proteins are raw legumes and whole grains. Given lectins' ability to bind to other foods, research suggests that they could disrupt digestion, weaken the intestines, and cause nutrient deficiencies.
If you eat foods with large amounts of lectin and notice you have symptoms, try soaking and cooking foods with lectins (such as dried beans and other legumes) before eating because doing so can decrease the lectin content by up to 50%.
Summary
Polyphenols are compounds naturally found in plant-based foods. They act as antioxidants and may help lower your risk for certain diseases. Examples of polyphenols include flavonoids, phenolic acid, polyphenolic amides, resveratrol, curcumin, and lignans.
The potential health benefits of polyphenols include a lower risk of heart disease, diabetes, cancer, inflammation, and cognitive decline. Foods that are rich in polyphenols include berries, beans, oats, garlic, spinach, and other plant-based foods.
While you can also get polyphenols from supplements, know that they are not regulated by the FDA. Make sure to talk to your provider before trying one.
Frequently Asked Questions
How much polyphenols should you ingest per day?
With current research, it’s not clear what dose of polyphenols to consume daily. However, researchers believe eating five or more servings of fruit and vegetables daily will provide enough polyphenols to benefit health.
Are polyphenols good for your gut?
Research shows polyphenols help support the health of your gut microbiome, which can keep intestines healthy, support digestion, boost the immune system, and support brain health.
Learn MoreWhat Is the Gut Microbiome?