The small towns baffling doctors with their lack of disease: Experts reveal the foods that could be responsible - and the modern diet they ALL reject

The science of longevity is becoming big business - and it's not just eccentric billionaires promising to help you live better for longer.

It seems every other beauty product, fitness program or cookbook these days comes with bold promises to turn back the clock.

And with an ageing population, the demand has never been greater for products and strategies that stave off the common health problems associated with old age.

But perhaps the answers to our questions about longevity have been staring us in the face the whole time.

For decades, scientists have been fascinated by the so called Blue Zones around the world that are home to the greatest number of centenarians, including Ikaria in Greece and Sardinia in Italy.

Blue Zones are geographic areas known for having older populations who are remarkably healthy, mobile and free of chronic disease.

Crucially, research shows these regions have some of the world's lowest rates of Alzheimer's and dementia - and 20 per cent less cancer.

Longevity expert Marcus Pearce has visited these small European towns and hosted group tours there since 2016 to better understand their unique way of life.

So, what's the secret? Well, it could be walnuts, amaranth leaves or samphire. But Pearce says two things are certain: no one is vegan and they're all socially active.

'What hits you instantly in these locations is you feel like you're going back in time,' Pearce, who lives near Byron Bay, tells me.

'The elders are physically and socially active, they're often gardening, working around the house, cooking, relaxing with friends with a coffee or wine.'

Interestingly, many are social smokers, which obviously isn't healthy, but perhaps the social aspect of a smoko may contribute to their overall wellbeing.

Sardinia, Italy

Sardinia, one of the five core 'Blue Zones', breaks a key ageing stereotype by having an equal number of male and female centenarians, which contrasts with global trends where five female centenarians exist for every one male centenarian.

The Sardinian diet generally consists of healthy wholegrains, beans, garden vegetables, fruits and olive oils, but locals also incorporate 'wild greens' into their diet.

We're not talking spinach or lettuce here, but rather a unique plant known as amaranth.

Clinical nutritionist Lee Holmes says the leaves, which are staples in soups, stews and salads, are a great source of calcium, magnesium and potassium, as well as vitamin K, all of which are essential for bone health and muscle function.

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Seulo, Italy

Seulo is a tiny town in the centre of Sardinia, with a population of fewer than 1,000.

While residents typically follow the aforementioned Sardinian diet, they add an extra special ingredient that might just be the key to their longevity.

'When locals couldn't easily access animal protein, they decided to plant more than 400 walnut trees in public spaces,' Pearce explains.

Holmes says walnuts, often described as a 'brain food', have many health benefits.

'The omega-3s and antioxidants in walnuts help lower cholesterol and reduce inflammation to help decrease heart disease risk, while their vitamin E and polyphenols support cognitive function and may protect against neurodegenerative disease,' she tells me.

They are also known to support beneficial gut bacteria, which is linked to improved immunity and reduced inflammation.

As well as snacking on walnuts, Seulo locals often incorporate them into meals such as salads or when baking biscuits and cakes.

Ikaria, Greece

One of the most striking things about life on the Greek island of Ikaria is its unhurried pace, where days unfold slowly and meals are built around fresh, seasonal ingredients - a lifestyle that's been linked to the islanders' remarkable longevity.

'In Ikaria, they're really great at living in the present moment. They're never in a rush. It makes you realise how fast we run our lives in Australia,' says Pearce.

When it comes to their healthy, fresh meals, he has noticed in the last decade the prevalence of samphire, also known as 'sea asparagus', in locals' diets.

The plant, described by Pearce as 'salty, crunchy and delicious', grows by the beach and is rich in potassium and magnesium.

'It stands out for its sea-derived antioxidants, such as fucoidans, and is a notable source of calcium, supporting bone strength,' adds Holmes.

Studies also show it can enhance antioxidant capacity, protect the liver and kidneys, and potentially help regulate blood pressure and metabolic health.

'These properties make samphire a unique, mineral-rich addition to a balanced diet,' she adds.

Live a slower life, but remain active

It's not just the food that contributes to living longer; it's the way of life.

'Living slower not only slows down your heart rate but it reduces blood pressure, lowers cortisol and improves your stress levels. All of a sudden you're in better health,' says Pearce.

Strong family connections are deeply embedded in the culture in both Italy and Greece; multi-generational households are common, as is living close to family members.

'Most of us focus on diets and exercise regimes. This isn't the case for the Blue Zones. They're just slowing down. They'd ask the average Australian, "Why are you rushing through life? Sit down, relax, have a cup of coffee or glass of wine."

'In Ikaria, they would say, "Why drive when you can walk?'"'

Other drastic differences are the lack of modern convenience stores and takeaway restaurants. You want spot a McDonald's or KFC on either of these islands.

And while Aussies tend to focus on strict exercise routines and structured gym workouts, elders in the Blue Zones don't put too much pressure on themselves.

They remain active in other ways, such as tending to their garden, going for walks or doing chores.

'Often you'll see men and women in their 80s, 90s and even older than 100 on the dancefloor getting raucous applause,' Pearce says.

'Age is celebrated - but in Australia it's all about anti-ageing and age is seen as a negative thing. Over in Ikaria and Sardinia, they have no idea that concept exists.'

Spend a day with the elders of Sardinia or Ikaria and you'll see the blueprint for a long, joyful life - morning walks through the hills, laughter over long lunches, and a deep sense of purpose that doesn't fade with age