Eating the Wrong Carbs May Raise Your Dementia Risk

A study by Universitat Rovira i Virgili finds that prioritizing low glycemic index foods, including most fruits and whole grains, may lower the risk of Alzheimer’s disease and other forms of dementia.

The amount and type of carbohydrates people eat may strongly influence the risk of developing dementia, according to a large population-based study. The findings, published in the scientific journal International Journal of Epidemiology, suggest that dietary carbohydrate patterns are closely linked to long-term brain health.

Age remains one of the strongest risk factors for dementia, but lifestyle choices also play an important role in protecting cognitive function. Diet is especially important, as carbohydrates account for about 55 percent of daily energy intake. Because they directly affect glucose and insulin metabolism, both the quantity and quality of carbohydrates consumed can shape metabolic health and influence the risk of conditions such as Alzheimer’s disease.

The research was conducted by the Nutrition and Metabolic Health (NuMeH) group at the Universitat Rovira i Virgili (URV), in collaboration with the Centre for Environmental, Food and Toxicological Technology (TecnATox) and the Pere Virgili Health Research Institute (IISPV).

Why glycaemic index matters

A central measure used in the study was the glycaemic index (GI), which reflects how rapidly a carbohydrate-containing food raises blood sugar levels after it is eaten. The scale ranges from 0 to 100. Foods like white bread and potatoes tend to have a high GI, meaning they cause faster spikes in blood glucose, while most fruits and whole grains have a lower GI and lead to slower increases.

To examine how these dietary patterns relate to dementia risk, the researchers analyzed data from more than 200,000 adults in the United Kingdom who were free of dementia at the beginning of the study. Dietary questionnaires were used to estimate both the glycaemic index and glycaemic load of each participant’s diet.

Over an average follow-up period of 13.25 years, 2,362 participants developed dementia. Using advanced statistical methods, the team identified the levels of dietary glycaemic index at which dementia risk began to rise, providing a detailed picture of how long-term carbohydrate choices may affect brain health.

Lower glycaemic diets reduce risk

The results showed that consuming foods with a lower glycaemic index is associated with a lower risk of developing dementia, whereas higher values increase the risk. Specifically, diets with a low to moderate glycaemic index were associated with a 16% reduction in the risk of developing Alzheimer’s, whereas higher values were associated with a 14% increase in risk.

“These results indicate that following a diet rich in low-glycaemic-index foods, such as fruit, legumes or whole grains, could decrease the risk of cognitive decline, Alzheimer’s and other types of dementia,” confirmed the study’s leader, Mònica Bulló, who is also professor in the URV’s Department of Biochemistry and Biotechnology, researcher at ICREA and director of the URV’s TechnATox Centre.

These results highlight the importance of taking into account both the quantity and quality of carbohydrates in strategies aimed at preventing and managing dementia.

Reference: “Glycemic index, glycemic load, and risk of dementia: a prospective analysis within the UK Biobank cohort” by Nil Novau-Ferré, Javier Mateu-Fabregat, Christos K Papagiannopoulos, Christos V Chalitsios, Laura Panisello, Georgios Markozannes, Konstantinos K Tsilidis, Mònica Bulló and Christopher Papandreou, 31 October 2025, International Journal of Epidemiology.
DOI: 10.1093/ije/dyaf182

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