While many of us know the importance of getting enough fibre, protein, and healthy fats, other, lesser-known nutrients often get overlooked. Polyphenols are a type of plant compound with powerful antioxidant and anti-inflammatory properties – and research suggests they’re incredibly good for us.
Luckily, polyphenols are found naturally in a large number of foods, so upping your intake can be fairly simple.
Here, we’ll take a closer look at what polyphenols are, the health benefits, and how you can add more to your diet.
What are polyphenols?
Polyphenols are a type of compound found in plant foods. They have anti-inflammatory properties and act as antioxidants, meaning they help to protect the body’s cells from damage caused by free radicals (unstable molecules).
Research has found that polyphenols may have several health benefits – including improved digestion, heart health, and protection against certain cancers.
There are over 8,000 types of polyphenols. However, the four main types are…
- Flavonoids – which account for over half of all the currently known polyphenols. Examples include anthocyanins and flavonols. Flavonoids are found in foods like berries, onions, tea, red wine, and soybeans.
- Phenolic acid – which accounts for around 30% of polyphenols. The two types of phenolic acid are hydroxybenzoic acid and hydroxycinnamic acid. Sources of phenolic acid include grapes, coffee, walnuts, and dark chocolate.
- Polyphenolic amides – polyphenolic amides are split into sub-groups called capsaicinoids and avenanthramides. Capsaicinoids are responsible for the heat of chili peppers; and avenanthramides are found in oats.
- Other polyphenols – some polyphenols only have one type and aren’t split into sub-groups. These account for a smaller portion of all polyphenols. Examples include resveratrol (unique to grapes and red wine); curcumin (found in turmeric); ellagic acid (found in some berries); and lignans (found in flaxseed, sesame seeds, and some other grains).
Beyond the number of polyphenols that a food naturally contains, other factors, such as the origin and ripeness of food – as well as how it was farmed, transported, stored, and prepared – can also impact the amount and type of polyphenols present.
Polyphenol-containing supplements are also available, however, further research is needed to confirm how safe they are. We’ll look at these in more detail later on.
What are the potential health benefits of polyphenols?
Polyphenols have been linked to several health benefits. For example…
1. Polyphenols may reduce the risk of type 2 diabetes
There’s evidence that polyphenols may lower blood sugar levels and reduce the risk of type 2 diabetes.
One reason for this is that polyphenols can help to prevent the breakdown of starch into simple sugars, which reduces the chance of post-meal blood sugar spikes. Other studies have found that polyphenols may stimulate insulin production – the hormone that keeps blood sugar levels steady by transporting sugar from the bloodstream into cells.
As a result of these findings, diets rich in polyphenols have been linked with lower blood sugar levels, higher sugar tolerance, and increased insulin sensitivity. And this study found that those who ate the most polyphenol-rich foods were less likely to develop type 2 diabetes than those who ate the least.
When it comes to reducing the risk of diabetes, research suggests that anthocyanins (typically found in red, blue, and purple foods like berries, grapes, and currants) may offer the greatest benefits.
2. Polyphenols may reduce the risk of heart disease
Polyphenols have been linked to improved heart health. Researchers believe this is largely down to their antioxidant properties and ability to lower chronic inflammation, which is a risk factor for heart disease.
Studies have linked polyphenols with higher HDL (good) cholesterol levels, and lower blood pressure and LDL (bad) cholesterol levels.
Enterolactone is a compound in the body, which research has linked with diets rich in lignans. Lignans are a type of polyphenol found in whole grains and flaxseed. This study revealed that people with higher enterolactone levels in their blood were 45% less likely to die from heart disease than those with low levels.
3. Polyphenols may improve digestion
Research suggests that polyphenols may support beneficial gut bacteria, fight off harmful bacteria, and improve digestion.
This study found that polyphenol-rich tea extracts increased the growth of good gut bacteria, including Bifidobacterium and Lactobacillus. Meanwhile, in other studies polyphenols fought off harmful bacteria, such as E. Coli and Salmonella. They may also improve symptoms of gastrointestinal diseases like inflammatory bowel disease (IBD).
Newer research has further added that polyphenols may help probiotics to grow and thrive. Probiotics are healthy gut bacteria. However, further studies are needed to confirm these findings.
4. Polyphenols may reduce the risk of cancer
Research has long drawn a link between whole, plant-based diets and a lower cancer risk. And experts are beginning to believe that polyphenols could be partly responsible for this.
Again, this is largely due to their antioxidant and anti-inflammatory properties, which studies suggest may help to block the growth and development of cancer cells.
In another study, high polyphenol intake was linked with a reduced risk of breast and prostate cancer. However, other studies reported no effects, so further research is needed to confirm the link.
5. Polyphenols may boost skin health
There’s evidence that polyphenols may boost skin health by offering protection from damage caused by the sun and pollution. This damage is the result of oxidative stress – an imbalance of free radicals and antioxidants that leads to cell damage.
The polyphenols in green tea particularly, have been widely researched for their potential sun-protective benefits.
Other studies have found that polyphenols may help to reduce the breakdown of collagen and elastin, slowing the process of skin ageing. For this reason, polyphenols are an ingredient in various cosmetic products.
Note: The benefits of nutrients like polyphenols are no replacement for wearing high-quality suncream to protect your skin from sun damage.
6. Polyphenols may improve brain function
Some studies have found that polyphenols may improve brain function – memory and focus.
In this study, drinking grape juice (which is naturally high in polyphenols) significantly improved memory in older adults in as little as 12 weeks.
Other studies have found that polyphenols may improve memory and attention by increasing blood flow to the brain.
There’s also evidence that the antioxidant effects of polyphenols may help to protect against and delay the onset of neurological disease like dementia and Alzheimer’s.
What are the best dietary sources of polyphenols?
Many healthy, plant-based foods contain polyphenols. We’ll cover some of the best sources below.
If you’re not sure where to start, eating a whole food, plant-based diet can be a useful guide.
Note: Many polyphenol-rich foods are high in fibre. Suddenly increasing your fibre intake can sometimes cause digestive issues like gas, bloating, and constipation – particularly if you suffer from gastrointestinal conditions like irritable bowel syndrome (IBS).
For this reason, some people find it helpful to introduce polyphenol-rich foods gradually.
Berries
Berries are high in polyphenols like anthocyanins, flavonols, and phenolic acid. Black chokeberries, native to eastern North America, have the highest polyphenol content.
However, some more common berries that are high in polyphenols include elderberries, blackcurrants, blueberries, blackberries, strawberries, and raspberries.
It’s important to note that anthocyanins – the polyphenols responsible for the colour of some fruit and vegetables – are mainly found in the berry skin. This means juices that don’t include the skin will lose much of their polyphenol content.
Other fruits high in polyphenols include apples, apricots, grapes, grapefruit, lemons, pomegranate, and nectarines.
Cocoa
There’s good news for chocolate lovers, as cocoa is a rich source of polyphenols.
However it’s important to note that not all chocolate is a good source of cocoa. For example, while dark chocolate contains around 1,600mg of polyphenols per 100g, milk chocolate contains just over 200mg. Meanwhile, white chocolate contains no cocoa.
Experts advise eating high-quality dark chocolate with a cocoa content of 70% or above.
Note: Chocolate is also high in calories and sugar, so it’s important to eat it in moderation.
Tea and coffee
If you like starting your day with a cup of tea or coffee, you’ll be pleased to know that both contain polyphenols. Though, it’s worth noting that the storage and roasting process of coffee beans affects their polyphenol content.
Research shows that organic coffee beans are higher in polyphenols than conventional ones. Polyphenol content has also been found to decrease over time, and lightly-roasted beans appear to have higher polyphenol content than medium-roast beans.
Spices
Many spices, including cloves, turmeric, and star anise, are fantastic sources of polyphenols.
That said, because we only use them in small amounts, spices provide fewer polyphenols overall.
Vegetables
Vegetables generally have lower polyphenol content than fruit. However, some contain more than others.
Vegetables with the highest polyphenol content include artichokes, red chicory, red onion, green chicory, shallots, carrots, and spinach.
Beans
Beans are packed with health-boosting nutrients, including polyphenols. Black beans and white beans are the richest sources.
Red wine
Drinking too much alcohol is known to negatively affect health. However, research suggests that some alcoholic drinks, such as red wine, may be good for us when enjoyed in moderation.
Red wine is produced using the skin of grapes, so contains more polyphenols than other wines.
Nuts and seeds
Nuts and seeds are fantastic sources of plant protein, nutrients, and polyphenols.
Those highest in polyphenols include flaxseed, chestnuts, pecan nuts, hazelnuts, and almonds.
Soy
Soy products with the richest polyphenol content include soy flour, tempeh, soy yoghurt, soy tofu, and soy milk.
Should I take polyphenol supplements?
There are many dietary sources of polyphenols. So, most people should be able to enjoy the benefits of these health-boosting compounds by eating a balanced diet centered around whole, plant-based foods.
Polyphenol-containing supplements are available to buy, but further research is needed to confirm how safe they are.
Supplements tend to deliver higher doses of polyphenols than what you’d get from food, and there’s evidence of negative side effects – including an increased risk of cancer, thyroid problems, and interactions with prescription medications.
Plus, experts advise that supplements are likely to be less beneficial than adding polyphenol-rich foods to your diet.
Note: It’s important to speak to your GP before adding any new supplements to your diet.
Final thoughts…
Polyphenols are health-boosting plant compounds, which research suggests we could do well to add more of to our diet. Luckily, they’re found naturally in many healthy, delicious foods, from berries and spices to coffee and nuts, so eating them can be enjoyable too.
For further reading, head over to the diet and nutrition section of our website. Here, you’ll find diet tips for everything from bone and heart health to keeping blood sugar levels stable.
Is your diet high in polyphenols? What changes are you currently making to improve your health? We’d be interested to hear from you in the comments below.
