New research is shedding light on how everyday eating habits might influence the risk of developing dementia in later life. This insight highlights the potential impact of how the body processes food over time on brain health, even in individuals who are not diabetic.

In one of the most extensive studies of its kind, scientists have identified a connection between sharp increases in blood sugar levels after meals and a heightened risk of Alzheimer’s disease, the most prevalent form of dementia. The implications of these findings are significant as they extend beyond those with chronic conditions.

For years, medical professionals have been aware that consistently high blood sugar, type 2 diabetes, and insulin resistance can harm the brain and elevate the risk of dementia. However, this new study suggests that even in the absence of diabetes, frequent spikes in blood sugar after eating—where glucose levels rise sharply and stay elevated—could be detrimental to brain health.

This groundbreaking research, conducted by a team at the University of Liverpool, involved analyzing health and genetic data from more than 350,000 individuals participating in the UK Biobank. This long-term study focuses on tracking the health of middle-aged and older adults, providing valuable insights into how lifestyle factors might contribute to dementia risk.

But the new findings suggest that repeated blood sugar ‘spikes’ after eating – where glucose levels surge and remain high – may also be harmful, even in people without diabetes.

The study, led by scientists at the University of Liverpool, analysed health and genetic data from more than 350,000 participants in the UK Biobank, a long-running study tracking the health of middle-aged and older adults.

Rather than measuring people’s diets directly, researchers examined genetic markers linked to how the body handles sugar – including blood glucose levels before eating, two hours after eating, and levels of insulin, the hormone that helps move sugar out of the bloodstream.

Together, these markers act as indicators of how efficiently the body processes food and controls blood sugar.

Everyone experiences dementia differently. Use this checklist to help you make a note of your symptoms before you talk to your GP.

Dementia is the UK’s biggest killer

Participants were aged between 40 and 69 at recruitment, with an average age of 59.9, and were followed up using medical records. 

Fifty-four per cent were female and 46 per cent male.

The researchers found that people who were genetically predisposed to higher blood sugar levels two hours after eating – a measure known as post-meal or postprandial glucose – were 69 per cent more likely to develop Alzheimer’s disease.

Importantly, the effect was not seen for fasting blood sugar, fasting insulin or insulin resistance, suggesting the risk may be specifically linked to how the body copes with sugar after meals.

‘This finding could help shape future prevention strategies, highlighting the importance of managing blood sugar not just overall, but specifically after meals,’ said study lead author Dr Andrew Mason.

Crucially, the researchers say the findings may be relevant well beyond people diagnosed with diabetes, as many individuals experience sharp rises in blood sugar after eating without being aware of it.

However, they stressed that the results should be interpreted with caution. When the team attempted to repeat the analysis using a separate international genetic dataset for Alzheimer’s disease, they were unable to replicate the finding.

The study also found no evidence that post-meal blood sugar spikes were linked to differences in brain size, hippocampal volume or markers of small vessel disease on MRI scans – suggesting the increased risk may not operate through obvious structural brain damage.

The research used a technique known as Mendelian randomisation, which analyses naturally occurring genetic differences to help infer cause-and-effect relationships while reducing the influence of lifestyle or environmental factors such as diet, weight or exercise.

Dementia is estimated to claim around 76,000 lives a year in the UK, making it the country’s biggest killer – often due to complications such as pneumonia or difficulty swallowing.

Alzheimer’s disease accounts for the majority of cases and currently affects around 982,000 people in the UK, a figure projected to rise to 1.4 million by 2040. 

Early symptoms typically include memory problems, difficulties with thinking and reasoning, and language impairment, which worsen over time.