What if something as simple as what you put on your plate could delay dementia, protect your heart, and help you live longer and healthier? That's a sweeping 15-year study by researchers at Sweden's prestigious Karolinska Institutet found: There's a strong and consistent link between healthy eating habits and the slower development of chronic illnesses among older adults.

“Our results show how important diet is in influencing the development of multimorbidity in aging populations,” Adrian Carbalio-Casla, a co-author and postdoctoral researcher at the Aging Research Centre, Karolinska Institutet, said in a media release.

Seniors in the study who followed one of the three healthier diets accumulated chronic conditions (such as heart disease and dementia) more slowly over time.

This wasn't a typical nutrition study. Rather than tracking a single nutrient or food, the research team looked at dietary patterns over time and how they impacted multimorbidity, or the development of two or more chronic diseases.

Nearly 2,500 older Swedish adults, all aged 60 and over, were followed by researchers for 15 years. Participants were living independently in the community. None was in assisted living or hospitals, but no one was perfectly healthy. Most had at least one chronic condition at the start of the study.

Researchers collected dietary data with food frequency questionnaires and assessed disease accumulation through both clinical assessments and national registry data.

The study classified participants' diets according to four distinct dietary patterns, three of which were low in salt, sugary beverages, alcohol, red and processed meats, and high in fruits, vegetables, nuts and whole grains, and a fourth that measured how much inflammation the foods they ate were likely to encourage:

The goal was to see if and how these different dietary patterns influenced whether a person developed cardiovascular, neuropsychiatric (including dementia) and musculoskeletal diseases.

There were clear winners — and losers. For instance, those participants who followed the MIND, AMED or AHEI diets accumulated chronic conditions more slowly over time. Most notably, these seniors experienced a slower onset of cardiovascular and neuropsychiatric conditions, including heart disease and dementia.

On the flip side, participants who scored the highest in terms of EDII saw a faster accumulation of chronic diseases, which is an outcome the researchers attributed to long-term, low-grade inflammation in the body.

Interestingly, none of the diets seemed to have a big effect on musculoskeletal conditions like arthritis or osteoporosis, though one analysis suggested AMED may be linked to faster accumulation of those particular diseases. However, this was a secondary finding and not statistically conclusive.

Participants with the most inflammatory diets saw a faster accumulation of chronic diseases because of long-term, low-grade inflammation.

Perhaps most importantly, the benefits were weaker in participants who already had multiple chronic illnesses at the start of the study. This suggests the biggest advantage comes from starting healthy eating habits earlier, before diseases develop.

Unlike many nutrition studies that rely on short term or cross-sectional designs, this one followed people over 15 years, with multiple dietary assessments and robust statistical models. It also emphasized real-world eating patterns rather than isolated nutrients.

The biggest lesson may be this: don't wait to eat better. That said, if you're already managing health issues, it's still not too late. The sooner you adopt a healthier diet, the more benefits you'll likely see.

One caveat: If you have a chronic disease like diabetes or arthritis, speak with your healthcare provider or a registered dietitian to tailor a dietary approach that works for your health status and goals before you make major dietary changes.

The study is published in Nature Aging.