Why The Type Of Carbs You Eat May Affect Dementia Risk: Low-GI Foods Matter

What you eat might influence not just your weight and heart health, but also how your brain ages. New research suggests that the type of carbohydrates in your diet. beyond how much you consume, may play an important role in your long-term risk of developing dementia, including Alzheimer's disease. Carbohydrates provide the bulk of daily energy intake for most people, but not all carbs are metabolised equally. A recent collaborative study led by nutrition researchers from the Universitat Rovira i Virgili and published in the International Journal of Epidemiology examined how carbs with different glycaemic index (GI) values affect dementia risk over time.

The glycaemic index is a ranking system (0-100) that indicates how quickly foods raise blood glucose levels after eating. Lower GI foods, such as whole grains, legumes and many fruits, cause slower and steadier increases in blood sugar, while high GI foods, like white bread and refined starches, trigger rapid spikes.

Analysing data from more than 200,000 adults in the UK Biobank cohort over an average of 13 years, researchers found a clear pattern. Diets built around low-GI carbohydrates were associated with lower dementia risk, while diets with higher GI values were linked to elevated risk. Understanding how carbohydrate quality intersects with brain health could help shape future dietary guidance for cognitive ageing and dementia prevention.

How Carbohydrate Quality Ties to Dementia Risk

In the large prospective analysis, more than 200,000 adults without dementia at baseline completed detailed diet questionnaires, allowing researchers to estimate the glycaemic index and glycaemic load of their habitual diets. Participants were then followed for an average of 13.25 years, during which 2,362 individuals developed dementia.

After adjusting for age, sex, lifestyle factors and other health variables, the study identified a clear relationship between dietary carbohydrate quality and dementia risk:

• Low to moderate GI diets were associated with a 16% lower risk of developing dementia, including Alzheimer's disease.
• In contrast, higher GI diets, those that cause rapid blood sugar spikes, were linked to a 14% higher risk of dementia.

Lead researcher Monica Bullo, professor of biochemistry and director of the TecnATox Centre at Universitat Rovira i Virgili, explained: "These results indicate that following a diet rich in low-glycemic-index foods, such as fruit, legumes or whole grains, could decrease the risk of cognitive decline, Alzheimer's and other types of dementia."

Glycaemic Index: Why It Matters

The glycaemic index ranks carbohydrate-containing foods based on how quickly they raise blood glucose. Foods with a high GI (e.g., white bread, sugary cereals) produce rapid blood sugar increases, which over years may strain metabolic systems. By contrast, low-GI foods (e.g., oats, lentils, brown rice, many fruits) lead to slower, steadier glucose absorption, which promotes more balanced insulin responses.

Growing evidence suggests that metabolic health, including how well the body handles glucose, is linked to brain ageing. Chronic high blood glucose and insulin dysregulation have been tied to inflammation, vascular issues and brain changes that underlie Alzheimer's and other dementias. While this study does not establish strict cause and effect, it adds to a pattern where better glucose regulation correlates with healthier cognitive ageing.

Mechanisms: How Carbohydrates May Influence the Brain

Several pathways may explain why carbohydrate quality affects dementia risk:

• Blood sugar control: Excessive blood sugar fluctuations may increase oxidative stress and inflammation, potentially damaging neurons over time.
• Insulin resistance: Long-term high GI diets can contribute to insulin resistance, a risk factor for both type 2 diabetes and dementia.
• Vascular health: High GI diets may harm cardiovascular systems that supply blood to the brain, increasing risk for vascular dementia.

Clinical evidence from related research also shows that high glycaemic load diets correlate with biomarkers linked to Alzheimer's disease pathology.

What This Means for Everyday Diets

While more research, especially randomized clinical trials in humans, is needed to establish direct causal links, the current findings reinforce existing nutrition advice:

• Choose low-GI carbohydrates like whole grains (e.g., brown rice, oats), legumes (beans, lentils), and most fruits.
• Limit high-GI foods such as white bread, refined grains, sugary snacks and processed cereals, which may contribute to rapid glucose spikes.
• Focus on balanced meals that include healthy fats, protein and fibre, all of which slow digestion and help control blood sugar.
• Public health guidance for cognitive ageing already emphasises diets like the Mediterranean or MIND diets, which are rich in plant foods and lower in refined carbs, patterns consistent with lower GI eating.

Emerging research indicates that not all carbohydrates are equal when it comes to brain health. Diets rich in low-glycaemic index foods, such as whole grains, legumes and fruit, were associated with a lower risk of dementia over more than a decade of follow-up in a large UK cohort. By contrast, diets high in fast-acting, high GI carbohydrates were linked to greater risk. These findings highlight the importance of carbohydrate quality, defined by how foods affect blood glucose, as a potential factor in cognitive ageing and dementia prevention. As science continues to explore diet-brain links, choosing carbohydrate sources that promote steady blood sugar may be a simple, actionable step for long-term brain health.

Disclaimer: This content, including advice, provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.