Research may have uncovered the secret to delaying chronic illness in old age. A study following more than 2,400 people for 15 years found that diet plays a key role in how many chronic diseases develop over time.
What the Study Found
Imagine two people in their 70s. Both are active, live independently, and enjoy life. But over the next 15 years, one develops two or three chronic illnesses—such as heart disease, diabetes, or depression—while the other remains relatively healthy. According to new research, diet may be a critical factor.
Researchers at the Aging Research Center at the Karolinska Institutet in Sweden followed more than 2,400 older Swedish adults for 15 years. They found that people who consistently ate a healthy diet developed chronic diseases more slowly compared to those whose diets were more inflammatory—high in processed meats, refined grains, and sugary drinks, which promote low-grade chronic inflammation.
This is significant because having multiple health conditions at once is one of the biggest challenges older people face, increasing the risk of disability, hospitalisation, and early death, while placing a huge burden on healthcare systems. While it has long been known that diet can help prevent individual diseases, this study shows it may also influence the overall pace of biological ageing.
Dietary Patterns Studied
The researchers examined 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. People who ate better were less likely to develop heart failure, stroke, depression, or dementia. However, no clear link was found between diet and musculoskeletal diseases such as arthritis or osteoporosis.
Some benefits were more pronounced in women and the oldest participants (aged 78 and above), suggesting that it is never too late to make dietary changes. Even in very old age, diet matters.
Why Diet Matters
One reason food has such strong potential is 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 reduce inflammation, while diets rich in highly processed foods and sugar do the opposite.
Another reason is that healthy diets support the body's resilience by providing essential nutrients that maintain immune function, muscle mass, and cognitive health. Over time, this can make a big difference in how people age.
This study is one of the longest and most comprehensive of its kind, using repeated dietary assessments and tracking more than 60 chronic health conditions. The findings were tested using different analytical methods to ensure they held up.
Practical Advice
Of course, diet is just one piece of the puzzle. Physical activity, social connections, and access to healthcare also play important roles. 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 studied, associated with slower ageing, better brain health, and fewer chronic diseases.
Ageing is inevitable, but people can shape how it unfolds. Even small changes in diet can make a meaningful difference in how people experience later life, regardless of their age.
