Did you know that polyphenols are regarded as ‘lifespan essentials’, thanks to their possible role in minimizing the risk of chronic diseases? Polyphenols are a group of compounds found in almost all plants. Many of the benefits associated with vegetarian diets such as the Mediterranean diet are attributed to the high polyphenol content of plant-based foods.
Here’s everything you need to know about polyphenols, including their top food sources.
Highlights
- Polyphenols are essential micronutrients with antioxidant and anti-inflammatory properties for sustaining life and healthy body functions,
- Being powerful antioxidants, polyphenols combat cell damage by neutralizing harmful free radicals produced during routine body functions,
- Research shows that more than 650 milligrams of polyphenols daily can increase the lifespan and support overall health.
A primer on polyphenols
Polyphenols are micronutrients essential for sustaining life and healthy body functions. They are chemicals found naturally in plants and plant-based foods. Research relates most of their health benefits to their antioxidant and anti-inflammatory properties, which decreases the risk of many chronic diseases.
Being powerful antioxidants, polyphenols combat cell damage by neutralizing harmful free radicals produced during routine body functions. These free radicals otherwise contribute to ageing and an increased risk of diseases like cancer, diabetes and heart disease.
Different plants contain different types of polyphenols. Although some foods are richer in polyphenols, the amount of these micronutrients depends on their origin, how they are farmed, how ripe they are and how they are stored and processed.
Research has identified more than 8000 types of polyphenols, which include the following three major categories:
- Flavonoids: Around 60 per cent of polyphenols belong to the category of flavonoids which include quercetin, kaempferol, catechins and anthocyanins. The top food sources of flavonoids include apples, onions, dark chocolate and red cabbage.
- Phenolic acids: This group constitutes 30 per cent of all polyphenols, including stilbenes and lignans. They are most commonly found in fruits, vegetables, whole grains and seeds.
- Polyphenolic amides: This category includes capsaicinoids and avenanthramides, found in abundance in chilli peppers and oats.
Other notable polyphenols include resveratrol in red wine, ellagic acid in berries and curcumin in turmeric.
Benefits of polyphenols
Research shows that more than 650 milligrams of polyphenols daily can increase lifespan and support overall health. However, research suggests that specific gene expressions may have a role to play in how the body responds to polyphenols.
Most benefits of polyphenols are associated with their ability to oxidize free radicals, which are damaging to cells. They may inhibit inflammation, regulate the body’s immune functions and combat allergic diseases.
1. Lower risk of type 2 diabetes
Various studies have found a link between polyphenol-rich diets and the risk of type 2 diabetes. One piece of research concluded that a polyphenol-rich diet lowered the risk of developing type 2 diabetes by 57 per cent as compared to subjects on a low-polyphenol diet. (8)
Research suggests that polyphenols may stimulate the release of insulin, the hormone responsible for lowering blood sugar levels and increasing glucose tolerance. They may also be responsible for preventing post-meal sugar spikes by suppressing the conversion of starch into simpler sugars.
Most anti-diabetic properties are associated with anthocyanins, a type of polyphenol, commonly found in red, purple and blue foods like berries and grapes.
2. Decreased risk of heart disease
Emerging evidence indicates that polyphenols may improve heart health due to their antioxidant effects and curb chronic inflammation. For example, enterolactone is formed during metabolism of lignan, a polyphenol commonly found in flaxseed. A study found that people with higher enterolactone levels had a 45 per cent less risk of fatal heart disease.
Other studies found that polyphenol supplements may increase high-density lipoprotein, or HDL, i.e. good cholesterol, and, conversely, lower low-density lipoprotein, or LDL, i.e. bad cholesterol, and blood pressure.
3. Better gut health
Various studies suggest that polyphenols are believed to weaken harmful bacteria and support the survival of beneficial gut bacteria. (17, 18, 19) Polyphenols may also help improve peptic ulcer disease (or PUD) and inflammatory bowel disease (or IBD).
4. Lower risk of cancer
Experts suggest that on account of the fact that they are strong antioxidants and anti-inflammatory agents, polyphenols may be the missing link between plant foods and could lower cancer risk.
While some studies noticed a link between reduced breast and prostate cancers and polyphenol intake, others found no correlation between them. Therefore, more research is needed to establish a stronger connection between polyphenols and cancer prevention and suppression.
5. Facilitation of regular blood flow
Polyphenols may prevent excessive blood-clot formation by suppressing platelet aggregation, (28, 29) which is when platelets in the blood begin to clump together to stop bleeding and form a clot.
However, excessive platelet clumping can sometimes block blood flow to essential organs, causing life-threatening health conditions like strokes, pulmonary embolism or deep vein thrombosis (or DVT).
6. Improved brain function
Emerging evidence suggests that flavonoids may regulate blood flow to the brain, improving working memory and attention, especially short-term memory and brain activity, in people with dementia.
Another study performed on older adults with mild mental impairment found that polyphenol-rich grape juice boosted memory significantly in as little as 12 weeks.
Foods that contain polyphenols
Although most plant-based foods have polyphenols, some food sources contain higher polyphenol content than others. Let’s have a look at some of the top polyphenol-rich food sources.
1. Berries and other fruits
Berries are one of the best sources of polyphenols, vitamin C, fibre and other essential nutrients. Chokeberries have the highest amounts, with 1123 milligrams of polyphenols in a half-cup serving.
Blackberries, raspberries and strawberries have 160 milligrams each per serving. The juice of fruits such as apples, grapes and pomegranates also contain high numbers of this micronutrient.
2. Herbs and spices
Herbs and spices are the best way to give your meals a polyphenol boost along with many minerals such as calcium, magnesium and potassium. Here are some of the top picks and their polyphenol content per tablespoon:
- Cloves: 239 milligrams
- Peppermint: 188 milligrams
- Star anise: 88 milligrams
Oregano, celery seeds, sage, rosemary and thyme each contain more than 13 milligrams of polyphenol per tablespoon.
3. Cocoa powder
Cocoa powder contains a whopping 516 milligrams of polyphenols in 1 tablespoon; however, it’s hardly possible to consume it all. Heating cocoa powder for cooking or processing it to create chocolates reduces its polyphenol content.
Dark chocolate has 249 milligrams of polyphenols per tablespoon, while milk chocolate has just 35 milligrams per tablespoon.
4. Nuts
Nuts are packed with essential fatty acids, proteins and fibres along with a good amount of polyphenols. Chestnut tops the list with 1405 milligrams per half-cup serving, followed by hazelnuts and pecans with 567 milligrams each and almonds with 215 milligrams per serving.
5. Beans
Navy, kidney and red beans are the top sources of polyphenols with 14.25, 16.73 and 15.23 milligrams of polyphenols per 100 grams, respectively.
6. Vegetables
Since almost all vegetables are good sources of polyphenols, you can easily get your daily dose of polyphenols by eating the recommended portion of vegetables (2–3 cups) daily. (41) The vegetables that pack in the highest polyphenols comprise artichokes, small red onions, fresh spinach or shallots
7. Olives
Besides being rich sources of vitamin E and fatty acids, olives are also an excellent source of polyphenols. Black olives have more polyphenols (113 milligrams per 20 grams) than the green ones (which contain 70 milligrams per 20 grams).
8. Coffee and tea
One cup of brewed coffee has roughly 35 milligrams of polyphenols. Black tea has around 120 milligrams of polyphenols per 100 millilitres, while green tea has 89 milligrams.
Risks associated with polyphenols
Most risks associated with polyphenol intake are related to polyphenol supplements. People with specific food allergies or medical conditions may also need to avoid certain polyphenol-rich foods. Otherwise, the routine use of such foods in one’s diet has been found to be safe for most people.
The risks and complications identified with excessive consumption of polyphenols include:
- Development of cancer,
- An increase in estrogenic activity,
- Interaction with certain medications,
- Effect on the absorption or bioavailability of other nutrients.
In multiple studies meant to assess the safety of polyphenols, kidney damage, thyroid problems and tumour developments were found in mice and other animals.
Much research is needed to figure out the interaction between polyphenol-rich foods and the absorption of certain nutrients. For example, certain plant teas can affect iron absorption, while grapefruit juice has been found to interact with various medications. Experts suggest that these may be related to the polyphenols found in foods.
Conclusion
Polyphenols are potent micronutrients found in plants. Vital research indicates that these compounds may play an essential role in keeping us healthy and preventing various diseases like diabetes, heart disease and various cancers. They are also associated with benefits like better gut health, prevention of blood clots and improved brain function.
Despite promising health benefits, more research is needed to fully assess the risks and benefits of taking excessive polyphenols, especially in supplemental doses. Till then, it’s best to make polyphenol-rich foods a significant part of one’s diet so as to load the body with polyphenols without any risks.
Disclaimer: The contents of this article are for general information and educational purposes only. It neither provides any medical advice nor intends to substitute professional medical opinion on the treatment, diagnosis, prevention or alleviation of any disease, disorder or disability. Always consult with your doctor or qualified healthcare professional about your health condition and/or concerns and before undertaking a new healthcare regimen including making any dietary or lifestyle changes.
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