Scientists may have found the single best diet for ageing well (2025)

This 30-year study might have revealed the secret to longevity

We all know the important role our diet plays in our health. Food plays a crucial role in our chances staying sharp, energetic, and disease-free as we age.

Maria Branyas Morera, who died in August 2024 at the grand old age of 117 years old, had officially been the world's oldest living person for about a year and a half.

Her secret to living a long and healthy life? Aside from the fact that scientists have revealed she was genetically blessed, Branyas had said she avoided alcohol and smoking, enjoyed daily walks, and followed a Mediterranean-style diet rich in fruits and vegetables – and even ate three yoghurts a day.

Now, new research has revealed the food groups that increase the likelihood of healthy aging – and even pinpointed the best diet overall.

The massive 30-year study of more than 100,000 people explored how diet impacts ageing and revealed which diet boosts your chances of ageing well, and which foods could be speeding up decline.

According to researchers, a plant-based, nutrient-rich diet, with moderate amounts of healthy animal foods like low-fat dairy, could hold the key to a longer and healthier life.

The study even highlights some shocking truths: poor diet might be just as harmful as smoking when it comes to ageing, speeding up the onset of things like diabetes, heart disease, and even impacting cognitive function.

Researchers tracked participants over three decades and found that a good diet was linked to a 45 to 85 per cent higher chance of ageing without major chronic disease.

People who stuck to healthy eating patterns, such as Mediterranean diets rich in olive oil, fish and fibre, and Dietary Approaches to Stop Hypertension (DASH) diets, which focus on fruits, vegetables, whole grains, and lean protein, were far more likely to maintain good mental and physical health as they aged.

What to eat for a long, healthy life

The study found that a greater intake of fruits, vegetables, whole grains, nuts, legumes and unsaturated fats was associated with better ageing. However, processed meats, trans fats and sodium were linked to worse outcomes.

The Alternative Healthy Eating Index (AHEI) came top of eight healthy dietary patterns analysed in the study. Developed by Harvard, the AHEI diet prioritises fruits, vegetables, whole grains, nuts, legumes, and healthy fats.

Olive oil and avocado: Those in the study who included unsaturated fats like olive oil and avocado in their diet had 40 per cent better physical function than those who didn't, beating even regular exercisers.

Plant foods: More fruits, veggies, whole grains and nuts in their diet were also linked to better ageing outcomes.

Avoid ultra-processed foods (UPF): In the study, fast food, snacks, and sugary treats were linked to poorer health and a 32 per cent lower chance of ageing well.

Animal-based foods: According to the study, low-fat dairy is good for healthy ageing when eaten in moderation. However, red meats and processed meats were linked to worse health outcomes.

"Our findings suggest that dietary patterns rich in plant-based foods, with moderate inclusion of healthy animal-based foods, may promote overall healthy aging and help shape future dietary guidelines," said co-corresponding author Marta Guasch-Ferré, associate professor in the Department of Public Health at the University of Copenhagen.

However, the authors also note that there is no single diet that works best for everyone.

"Our findings also show that there is no one-size-fits-all diet," said Anne-Julie Tessier, a professor of nutrition from the University of Montreal in Canada. "Healthy diets can be adapted to fit individual needs and preferences."

The study was published in the journal Nature Medicine.