What are polyphenols: Health effects and sources of these antioxidants

Polyphenols are natural antioxidants that have a beneficial effect on the human body. Their regular consumption supports digestion, strengthens brain health and protects against heart disease or type 2 diabetes. Which foods contain the most of these health-promoting micronutrients?

Polyphenols are micronutrients that occur naturally in plants. Red wine, dark chocolate, tea and berries are just a few of the most well-known natural sources. Many other foods also offer significant amounts of these antioxidants. In addition to natural sources, polyphenols can also be found in many dietary supplements.

In this article, you’ll learn everything you need to know about polyphenols, including the positive effects and various sources of these health-promoting antioxidants.

What are polyphenols?

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

Studies show that polyphenols are powerful antioxidants. In this role, they prevent damage to your cells caused by aging, a polluted environment or an unhealthy lifestyle. Over time, this damage is associated with an increased risk of many chronic diseases such as cancer, diabetes and heart disease. In addition, polyphenols are also thought to reduce inflammation, which is thought to be a major cause of many chronic diseases.

Types of polyphenols

To date, more than 8,000 types of polyphenols have been identified and can be divided into 4 main groups:

  • Flavonoids: These make up about 60% of all polyphenols. Examples include quercetin, kaempferol, catechins and anthocyanins, which are found in foods such as apples, onions, dark chocolate or red cabbage.
  • Phenols: This group accounts for about 30% of all polyphenols. Examples include stilbenes and lignans, which are mostly found in fruits, vegetables, whole grains and seeds.
  • Polyphenol amides: This category includes capsaicinoids, which are found, for example, in chilli peppers, and avenanthramides, which are found, for example, in oats.
  • Other polyphenols: This group includes resveratrol, which is found in red wine, ellagic acid, which is typical of berries, curcumin, naturally found in turmeric, and lignans, which are found, for example, in flax or sesame seeds and whole grains.

The amount and type of polyphenols in food depends on the food – factors such as the origin of the food, its maturity and the way it has been grown, transported, stored and then prepared for consumption.

Natural sources of polyphenols

Most plant foods such as vegetables, fruits and whole grains contain polyphenols. To boost your health, it’s easy to take enough in your diet, however, remember that some sources are more nutritious than others.

Below are the natural foods that have the highest polyphenol content, in addition to other essential nutrients.

Berry fruits

Berries are low in calories and high in vitamin C, fibre and polyphenols, making them a nutritious component of any diet.

Chokeberries have the highest amount of these antioxidants – namely 1,123 polyphenols per serving (about half a cup). Second in order are elderberries, which contain 870 milligrams of polyphenols per serving. Many other common berries are also high in polyphenols, including:

  • Blueberries with 535 milligrams
  • Blackcurrants with 485 milligrams
  • Blackberries, raspberries and strawberries with about 160 milligrams
  • Dark grapes

Herbs and spices

To enrich your food with polyphenols, reach into your spice cabinet. In addition to high levels of polyphenols, dried herbs and spices often contain a variety of other nutrients such as calcium, magnesium, and potassium. Spices with the highest polyphenol content include:

  • Cloves
  • Peppermint
  • Aniseed
  • Oregano
  • Sage
  • Rosemary
  • Thyme

Cocoa powder

High-quality cocoa powder is a potent source of polyphenols – one tablespoon contains up to 516 milligrams. However, remember that heating and processing cocoa powder to make chocolate products can reduce this content. Dark chocolate, for example, contains 249 milligrams per tablespoon, while milk chocolate has only 35 milligrams.


Nuts are an easy way to add fibre, protein and essential fatty acids to your diet, but because they are high in calories, you should moderate your daily portion of nuts. Most nuts contain polyphenols, with chestnuts containing the most ever. Approximately 3 fruits have about 347 milligrams of these micronutrients. Other good sources of polyphenols include hazelnuts and pecans.


Flaxseed is sometimes used to improve digestion and relieve constipation. Along with its high fiber content, it also contains 229 milligrams of polyphenols per tablespoon. Flaxseeds can be added to cereals and salads or baked into crackers, cookies or homemade breads.


Experts recommend eating 3 to 5 servings of vegetables a day. Because most vegetables contain polyphenols, getting enough vegetables in your diet will help you take advantage of the health benefits of these antioxidants. Some of the vegetables with the highest levels of polyphenols include:

  • Broccoli
  • Fresh spinach and leafy greens in general
  • Asparagus
  • Artichokes
  • Carrots
  • Shallots
  • Red onions


Olives are rich in vitamin E, fatty acids and polyphenols. Twenty grams of black olives (about five olives) contain 113 milligrams of polyphenols, while the same serving of green olives contains about 70 milligrams.

Coffee and tea

If you start your day with a cup of coffee or tea, you are adding polyphenols to your diet. Twenty grams of coffee – roughly the amount to make one brewed cup – contains about 35 milligrams of polyphenols. Similarly, black and green tea also contain these antioxidants.

Recommended daily allowance of polyphenols

Although polyphenol deficiency is not linked to specific health problems, polyphenols are considered micronutrients that have the potential to protect your body and reduce the risk of chronic diseases.

Studies show that people who follow a diet rich in polyphenols – consuming more than 650 milligrams per day – have a lower risk of chronic disease than those who consume less than 500 milligrams per day.

Effect of polyphenols on human health

Polyphenols have been associated with various positive effects on human health. What are their specific health benefits to the human body?

Lowering blood sugar levels

Polyphenols can help lower blood sugar levels, which contributes to a lower risk of developing type 2 diabetes. This is partly because polyphenols can prevent starch from breaking down into simple sugars, reducing the likelihood of blood sugar spikes after eating.

These compounds may also help stimulate the secretion of insulin, a hormone that is needed to move sugar from the bloodstream into cells and keep blood sugar levels stable.

It is predominantly one type of polyphenol – anthocyanin – that may offer the strongest antidiabetic effect. Anthocyanins are most commonly found in red, purple and blue foods such as berries, currants and grapes.

Reducing the risk of heart disease

Adding polyphenols to your diet can improve heart health. Experts believe that the positive effect of polyphenols on the cardiovascular system is largely due to the antioxidant properties of these substances, which help reduce chronic inflammation, a risk factor for the development of heart disease.

Recent studies have also linked polyphenol supplements to a reduction in blood pressure and LDL (bad) cholesterol levels while increasing HDL (good) cholesterol.

Reducing the risk of blood clots

Polyphenols can reduce the risk of blood clots. Blood clots form when platelets circulating in your bloodstream start to clump together. This process is known as platelet aggregation and is helpful in preventing excessive bleeding.

However, excessive platelet aggregation can cause blood clots that can have negative health effects, including deep vein thrombosis, stroke and pulmonary embolism. Polyphenols can help to reduce the process of platelet aggregation, thereby preventing the formation of blood clots.

Protection against cancer

Research has linked a plant-rich diet to a lower risk of cancer, and many experts believe that polyphenols are partly to blame.

Polyphenols have powerful antioxidant and anti-inflammatory effects that may be beneficial in preventing cancer by helping to block the growth and development of various cancer cells.

Supporting healthy digestion

Polyphenols can benefit digestion by promoting the growth of beneficial gut bacteria while fending off harmful ones. For example, evidence suggests that tea extracts rich in polyphenols may promote the growth of beneficial bifidobacteria (some of the most common probiotic bacteria).

Note: Probiotics are live microorganisms that have health benefits for the human body when consumed regularly. They can be found in yogurt and other fermented foods, dietary supplements and cosmetic products. How to choose the best probiotics?

In addition, green tea polyphenols can help fight harmful bacteria such as Escherichia coli or salmonella bacteria, as well as improve the symptoms of peptic ulcer disease and inflammatory bowel disease.

Support brain function

Foods rich in polyphenols can improve concentration and memory. One study reported that drinking grape juice, which is naturally rich in polyphenols, helped significantly improve memory in older adults with mild intellectual disability in just 12 weeks.

For example, the flavanols in cocoa can improve blood flow through the brain, which is why this type of polyphenol is associated with improved memory and attention.

Similarly, the polyphenol-rich plant extract Ginkgo biloba appears to promote memory, learning and concentration. It is also associated with improved brain activity and short-term memory in people with dementia.


Polyphenols are beneficial plant compounds with antioxidant properties that can help you maintain your health and protect against various diseases. They can improve digestion, brain function and blood sugar levels, as well as protect against blood clots, heart disease and certain cancers.

Therefore, include as many natural sources containing these micronutrients in your diet as possible, and dietary supplements can be another way to increase your intake of healthy compounds.