Imagine two people in their 70s. Both are active, live independently and enjoy life. But over the next 15 years, one of them develops two or three chronic illnesses – heart disease, diabetes, depression – while the other remains relatively healthy. What made the difference?

According to our new research, diet may be a key part of the answer.

In our new study, our group at the Aging Research Center at the Karolinska Institutet, Sweden, followed more than 2,400 older Swedish adults for 15 years.

We found that people who consistently ate a healthy diet developed chronic diseases more slowly, in contrast to those whose diets were considered more inflammatory; that is, diets high in processed meats, refined grains and sugary drinks, which are known to promote low-grade chronic inflammation in the body.

This is important because having several health conditions at the same time is one of the biggest problems older people face. It increases the risk of disability, hospitalisation and early death. It also places a huge burden on healthcare systems. But while it has been long known that diet can help prevent individual diseases, our study shows that it may also influence the overall pace of biological ageing.

It found that it is never too late to make changes (Getty/iStock)

We looked at four well-known dietary patterns. Three of them – the Mind diet (designed to protect brain health), the Alternative Healthy Eating Index (based on foods linked to lower disease risk) and the Mediterranean diet – were associated with slower disease accumulation. The fourth, a diet high in inflammatory foods, was linked to faster accumulation.

The strongest associations were seen for cardiovascular and psychiatric conditions. So, people who ate better were less likely to develop diseases including heart failure, stroke, depression or dementia. We did not, however, find a clear link between diet and musculoskeletal diseases such as arthritis or osteoporosis.

Some of the benefits of healthy eating were more pronounced in women and in the oldest participants: those aged 78 and above. This suggests that it is never too late to make changes. Even in very old age, diet matters.

Why does food have such a strong potential? One reason may be inflammation. As people age, many develop low-grade chronic inflammation – sometimes called “inflammaging” – which is linked to a wide range of diseases. Diets high in vegetables, fruits, whole grains, and healthy fats tend to reduce inflammation. Diets rich in highly processed foods and sugar do the opposite.

About the authors

Adrián Carballo Casla is a Postdoctoral Researcher in Geriatric Epidemiology at Karolinska Institutet.

Amaia Calderón-Larrañaga is an Associate Professor at the Aging Research Center at Karolinska Institutet.

David Abbad Gomez is a PhD Candidate in the Department of Epidemiology and Evaluation at Hospital del Mar Research Institute, Barcelona.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Another reason is that healthy diets support the body’s resilience. They provide essential nutrients that help maintain immune function, muscle mass and cognitive health. Over time, this can make a big difference in how people age.

Our study is one of the longest and most comprehensive of its kind. We used repeated dietary assessments and tracked more than 60 chronic health conditions. We also tested our findings using different analytical methods to make sure they held up.

Healthy diets support the body’s resilience (Getty Images)

Of course, diet is just one piece of the puzzle. Physical activity, social connections and access to healthcare all play important roles in healthy ageing. But improving diet quality is a relatively simple and accessible way to help older adults live longer, healthier lives.

So what should older adults eat? The message is clear: eat plenty of vegetables, fruits, legumes, nuts and whole grains. Choose healthy fats like rapeseed oil and fish. Limit red and processed meats, sugary drinks and solid fats.

These are the building blocks of the diets we studied – and they have been associated with slower ageing, better brain health and fewer chronic diseases in this and other research.

Ageing is inevitable. But people can shape how it unfolds. Our findings suggest that even small changes in diet can make a meaningful difference in how people experience later life, regardless of their age.