High red meat and sugary drinks tied to faster onset of dementia and chronic disease in 15-year study

A 15-year observational study of almost 2,500 older adults found that diets high in red and processed meat and sugary fizzy drinks were associated with a faster accumulation of dementia, cardiovascular and other chronic illnesses, while Mediterranean-style and other healthy dietary patterns were linked with significantly fewer long-term conditions.

Researchers analysed data from the Swedish National study on Aging and Care in Kungsholmen (SNAC-K), following participants for up to 15 years. The average age at baseline was 71 and just over half of participants were women. Diet quality was assessed repeatedly using food questionnaires and scored against several recognised dietary patterns, including the Mediterranean diet, the MIND diet, the Alternative Healthy Eating Index (AHEI) and the Empirical Dietary Inflammatory Index (EDII). The study was published in the journal Nature Aging.

The investigators examined "multimorbidity," defined as the total number of chronic illnesses a person accumulated with age, rather than focusing on single diseases. Conditions counted included heart disease, stroke, dementia and other neuropsychiatric illnesses such as Parkinson’s disease and depression, as well as diabetes, cancer and musculoskeletal problems such as arthritis and osteoporosis. Participants whose diets most closely resembled the Mediterranean, MIND or AHEI patterns developed fewer chronic conditions over the follow-up period; by the end of the study, those with the healthiest diets had on average two to three fewer chronic diseases than those with the poorest diets.

Diet quality showed the strongest associations with cardiovascular and neuropsychiatric illnesses; the researchers found little association between diet and age-related musculoskeletal conditions. A diet scoring highly on the Empirical Dietary Inflammatory Index — characterised by large amounts of red and processed meats, sugary drinks and other processed products — was associated with faster disease accumulation.

Co-author Adrián Carballo-Casla, a postdoctoral researcher at the Aging Research Centre at the Karolinska Institutet, said the findings "show how important diet is in influencing the development of multimorbidity in ageing populations." The authors noted that the protective associations were particularly marked among women and among the "oldest old," those aged 78 and older.

The study did not assign participants to specific diets; it analysed usual eating patterns and their relationship with later health. As an observational study, it cannot prove causation, the authors and independent experts said, but it adds to a growing body of evidence linking diet quality with healthy ageing. The researchers suggested that improved diet quality may slow "inflammaging," a term for chronic, low-grade inflammation that accumulates with age and contributes to multiple diseases.

Public-health researchers and clinicians have raised concerns about the rising consumption of ultra-processed foods, which are typically high in added fat, sugar and salt and low in fibre and protein. A separate April 2025 study cited by the authors estimated that ultra-processed foods make up more than half of the British diet and may be linked to as many as 18,000 premature deaths annually through associations with diabetes, cancer, heart disease and depression.

Dementia and cardiovascular disease remain major burdens for ageing populations. In the UK, dementia affects about one in 11 people aged 65 and over, and more than one million Britons are projected to be living with the condition by 2030. Globally, dementia cases are projected to rise substantially as populations age, and heart disease and stroke together account for a large share of deaths and long-term disability.

Health guidance used by the study authors and national health services emphasises whole foods and limits on processed items. Public recommendations include basing meals on starchy carbohydrates such as potatoes, bread, rice or pasta, preferably wholegrain; consuming at least five portions of a variety of fruit and vegetables daily; including beans, pulses, fish, eggs, meat and other proteins with at least two portions of fish a week, one of which should be oily; choosing unsaturated oils and spreads in small amounts; aiming for about 30 grams of fibre per day; keeping sugar, salt and saturated fat intake low; and drinking adequate fluids.

The study's authors said the next steps are to identify the specific dietary recommendations that could have the greatest impact on longevity and to determine which groups of older adults — by age, sex, socioeconomic background and existing conditions — are most likely to benefit from dietary changes. They emphasised that improving diet quality in older populations could be an important component of strategies to reduce the burden of multimorbidity as societies age.