Everyone knows vitamins and minerals are important - but as a result, they often get all the attention. Ask anyone to name a nutrient, and they'll reach for vitamin C, or maybe iron, before anything else comes to mind.
Polyphenols rarely get a mention, even though researchers have identified several hundred different ones in edible plants - and a growing body of evidence suggests they matter just as much as the nutrients we do know by name.
So what exactly are they, and why do scientists keep circling back to them when they try to explain why the Mediterranean diet seems to protect against so many different conditions at once?
What are polyphenols?
Polyphenols are tiny natural compounds made by plants, mostly as a form of self-defence against UV light, pests, and disease. They also happen to be responsible for a lot of the vibrant colour in fruit and vegetables, which is why the foods richest in polyphenols tend to be the ones that look the most striking on a plate.
They fall into several large families, including flavonoids, phenolic acids, lignans and stilbenes, each behaving slightly differently once inside the body. No single polyphenol does everything, which is exactly why eating a wide variety of colours matters more than fixating on any one superfood.
It’s the synergistic effect from combining different coloured plant foods that is important for maintaining health.
What are they actually doing in the body?
Most of the interest comes down to antioxidant activity and anti-inflammatory activity. Once in your body, polyphenols get busy:
• Mopping up free radicals. Normal metabolism, pollution, UV exposure and stress all generate unstable molecules called free radicals, which damage cells and DNA over time. Polyphenols neutralise a good number of these before they can do harm, which is the basic definition of an antioxidant.
• Calming inflammation at a molecular level. Research has shown polyphenols can switch off some of the signalling pathways that drive chronic low-grade inflammation, the kind strongly linked to heart disease, diabetes and dementia.
• Protecting blood vessels. Some polyphenols appear to support the lining of blood vessels directly, helping them relax and dilate properly, which plays into healthy blood pressure.
• Feeding the gut. A large proportion of the polyphenols we eat aren't absorbed in the small intestine. Instead, they travel to the colon, where gut bacteria break them down and benefit from them. So, they act as pre-biotics and post-biotics
A 2018 review in Nutrients concluded that polyphenols regulate immune function by interfering directly with inflammatory signalling and gene expression, rather than simply acting as passive antioxidants mopping up damage after the fact.
The gut-brain connection
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One of the more interesting threads of research concerns the gut microbiome. Polyphenols act as fuel for beneficial gut bacteria, and in return those bacteria convert them into smaller, more active compounds the body can use.
A 2022 study published in Frontiers in Ageing Neuroscience explored how this gut-brain relationship might help protect against neurodegenerative conditions, such as Alzheimer's, via pathways that link gut bacteria, inflammation and brain health. It's an area still being actively researched, but it adds another layer to why polyphenols support brain health over the long term.
What does the evidence show for disease risk?
Diets consistently high in polyphenols have been linked with a lower risk of cardiovascular disease, type 2 diabetes, osteoporosis, certain cancers and neurodegenerative conditions in long-term population studies. So, polyphenols have a positive role in almost every body system.
Olive oil polyphenols in particular have been singled out. A 2021 review in Antioxidants described their therapeutic effects against a whole cluster of chronic conditions, from cardiovascular disease to neurodegenerative disorders, and pointed to their role in reducing the oxidative stress behind much age-related decline.
Separately, a review in Frontiers in Nutrition noted their antibacterial and antioxidant properties, which make them promising candidates for supporting long-term health well beyond a single organ system.
Why colour is really the key
It's tempting to hunt down whichever single food contains the highest polyphenol count and eat plenty of it. But bioavailability - how much of a compound the body can actually absorb and use - varies enormously between different polyphenols, and even between people, depending on gut bacteria and how a food is prepared.
That's the real argument for variety over volume. Since different colours contain different families of polyphenols, eating a broad mix of colourful plant foods gives the body access to a much wider range of these compounds than relying on the same few vegetables, however impressive their individual numbers look on paper.
Combining colourful fruits, vegetables and herbs is a habit at the centre of what makes the Mediterranean diet effective. It naturally builds meals around a rotating cast of vegetables, fruit, herbs, and olive oil rather than any single hero ingredient.
Part of a Series
This article is part of series on staying healthy as you get older and improving your quality of life.
It’s not only a goal almost everyone shares, but has huge implications on national healthcare spending, productivity and economic resilience.
It strongly recommends the Mediterranean diet as the best way of eating but recognises that maintaining strength and aerobic fitness is also a critical part of a healthy ageing lifestyle.
It also suggests a supplement to help reach the increased plant nutrient levels that you need as you get older.
DailyColours® contains 161 plant nutrients – nutrients that are missing from an ordinary vitamin and mineral pill. Clinical trials show that it offers Mediterranean diet benefits in a daily supplement. You can see it here.
Note: The content on this site is intended for general wellness and informational purposes only. It is not personalized medical advice. Consult a healthcare professional before making any changes to your diet, exercise, or lifestyle routines.