Eating a Mediterranean diet that is rich in fruit, vegetables and whole grains may not protect against Alzheimer’s, a study has found.
For years, scientists have thought the diet protects the brain. But a two-decade long study has found no such link.
Experts today said the research offers ‘convincing evidence’ that eating healthily does not slash the risk of developing dementia.
But charities for the memory-robbing disorder have today urged caution against the findings of the French study, pointing out several flaws.
For years, scientists have thought the diet protects the brain. But a two-decade long study has found no such link
Some 850,000 people in the UK have dementia, and the number is expected to soar to one million by 2025 and two million by 2050.
Figures show nearly six million people in the US have Alzheimer’s – the most common form of dementia.
Université de Montpellier researchers tracked nearly 8,200 healthy adults without dementia from when they were first recruited in the early 1990s.
Volunteers, who were all civil servants in the UK, were asked to complete food questionnaires, to allow experts to assess the quality of their diets.
After following the participants until 2017, the scientists recorded exactly how many of them were officially diagnosed with dementia.
A healthy diet included eating lots of vegetables, fruits, whole grains, nuts and legumes, omega-3 fatty acids and polyunsaturated fats.
In contrast, a poor diet consisted of consuming plenty of sugar-sweetened drinks and fruit juices, red and processed meat, trans fats and salt.
Researchers, led by Dr Tasnime Akbaraly, separated the volunteers into three groups, depending on how healthy their diet was.
They then compared the rates of dementia among the groups. But they found ‘no significant difference’.
Dr Akbaraly and colleagues found roughly 1.75 and 1.8 cases of dementia would be diagnosed for every 1,000 person-years in the groups.
The study, published in the Journal of the American Medical Association, received criticism from experts in age-related diseases.
Professor Tom Sanders, of King’s College London, warned the study did not delve into other lifestyle aspects known to raise the risk of dementia, such as smoking.
Professor Clive Ballard, of the University of Exeter, said the power of the study – called the Whitehall II – was ‘very limited’.
He added that the ‘strongest evidence’ to date suggests there is some benefit from following a Mediterranean diet.
Charities today warned self-reported questionnaires ‘may not always be accurate’ and that not everyone with dementia would have been diagnosed.
Dr James Pickett, head of research at the Alzheimer’s Society, said: ‘Dementia is one of the top ten causes of death, and the only one we can’t cure, prevent or even slowdown.
‘It’s estimated that up to a third of cases of dementia could be prevented by changes in lifestyle, including diet.
‘So it’s surprising that this study suggests that diet in midlife does not have an impact on risk of dementia in later life.
He added: ‘What we do know is that there are lots of factors which contribute to the development of dementia; some of which we can control.
Dr Sara Imarisio, head of research at Alzheimer’s Research UK, called for more trials of a similar length to investigate the causes of dementia.
But she added the study, which was observational – meaning it cannot prove certain variables cause the differences it spots, ‘may not tell the whole story’.
Dr Imarisio said: ‘This research doesn’t tell us whether a healthy diet might affect dementia risk in combination with other aspects of healthy living.’
She said the exact link between diet and dementia remains unclear but added the ‘best current evidence’ suggests it may play a role in keeping a healthy brain.
But Professor Robert Howard, of University College London said: ‘The study provides convincing evidence that eating a good quality diet… does not reduce later risk of cognitive decline or dementia.
‘The results are disappointing because they remove a potential easily modifiable dementia risk factor from the table.’
However, Professor Horward warned the findings should not encourage middle-aged adults to scrap healthy diets.
He added: ‘Obesity and diabetes are convincingly linked to higher dementia risk and the additional cardiovascular health benefits of a good diet are overwhelming.’