Everyday eating habits could play a role in dementia risk later in life, new research suggests.
Scientists say this may be because the way the body processes food over time can influence brain health, even in people who do not have diabetes.
In one of the largest studies of its kind, researchers have linked sharp rises in blood sugar after meals to a higher risk of developing Alzheimer’s disease, the most common form of dementia.
Doctors have long known that chronically high blood sugar, type 2 diabetes and insulin resistance can damage the brain and increase 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.
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.
