A major review involving more than 62,500 adults suggests that following certain diets could cut your risk of cognitive decline in old age by as much as 40 per cent.
Scientists at Shandong University in China analysed 15 studies of people over 60 and found that those following the Mediterranean or MIND diets were significantly less likely to develop memory and thinking problems than those with less healthy diets.
The Mediterranean and MIND diets are very similar. Both include a lot of vegetables, fruit, legumes, nuts, seeds and whole grains, as well as a moderate amount of fish, poultry and dairy. Meanwhile, processed foods, red meat and sugar are limited.
However, while the Mediterranean diet is inspired by a particular region, the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet was specifically developed to protect the brain from age-related decline.
The Mediterranean diet emphasises certain culturally significant ingredients, such as olive oil, but the MIND diet prioritises nutrient-rich foods such as berries and green leafy vegetables – both thought to protect the brain from inflammation.
Scientists have long suspected that what we eat affects how our brains age, but the evidence has been mixed. To get a clearer picture, the team at Shandong University combined data from 15 studies to better understand the relationship between what we eat and how our brains fare in old age – and by extension, our risk of associated diseases, such as dementia.
The studies included appear to have quite different results. But, when combined, they suggested that older adults who ate healthily were significantly less likely (40 per cent) to experience cognitive decline, compared to participants with less healthy diets.
Therefore, the scientists concluded that older adults should be encouraged to eat vegetables, fruit, fish and legumes at every meal.
However, scientists who were not involved with this research have told BBC Science Focus that this study should be interpreted cautiously, because the link between diet and cognitive health is very complex.
Prof Keith Frayn, Emeritus Professor of Human Metabolism at the University of Oxford, said: “This study shows convincingly that a healthier diet is associated with better cognitive function in elderly people."
Frayn cautioned that the study doesn't definitely show that a better diet causes better brain health. The studies included in this analysis were observational, he explained, so the link might be caused by other factors, such as wealth, privilege, or healthy habits unrelated to diet.
“This doesn’t mean we shouldn’t aim for a healthy diet as we get older for many reasons, but it is wrong to suggest that diet alone might change our cognitive function,” Frayn added.
But Dr Oliver Shannon, a nutrition and ageing lecturer at Newcastle University, told BBC Science Focus that this study’s findings – that consuming a healthier diet later in life could have benefits for the brain – were consistent with previous research, including some recent clinical trials. So, there could be a causal link here.
“Making small dietary changes towards a healthier diet, such as eating more vegetables, pulses, wholegrains and fish, could help older adults better maintain their memory and thinking skills as they age,” he said.
Read more:
- How to live longer: The biggest lessons from the Mediterranean diet
- Here's the best diet for keeping your brain young, according to neuroscientists
- 8 foods you should eat for a healthier, happier brain, according to science
About our experts
Prof Keith Frayn is an Emeritus Professor of Human Metabolism at the University of Oxford, UK, as well as an Emeritus Fellow of Green Templeton College, Oxford. Frayn's work covers metabolism and nutrition, and he has written numerous books, including his textbook, Human Metabolism: a Regulatory Perspective.
Dr Oliver Shannon is a lecturer in nutrition and ageing in the Human Nutrition Research Centre at Newcastle University, UK. His research primarily explores the impact of nutrition, including diets such as the Mediterranean diet, on cognitive and cardiovascular ageing. Shannon has published more than 80 peer-reviewed journal articles in leading nutrition journals.
