Associated with less tissue loss, especially grey matter-brain's information processing hub
The combined Mediterranean and blood pressure lowering diet (MIND) may slow the structural changes related to brain ageing, finds research published online in the Journal of Neurology Neurosurgery & Psychiatry.
This diet is associated with less tissue loss over time, especially grey matter-the brain's information processing hub, with a key role in memory, learning, and decision-making-and less ventricular enlargement, which reflects brain atrophy, where tissue loss is accompanied by the enlargement of cerebrospinal fluid-filled spaces.
The Mediterranean-Dietary Approaches to Stop Hypertension Diet Intervention for Neurodegenerative Delay diet, or MIND for short, has previously been linked to better cognitive health, note the researchers.
The diet recommends the regular consumption of particular food groups: green leafy vegetables; other vegetables; berries; nuts; whole grains; fish; beans; olive oil; and poultry, plus a moderate intake of wine. And it recommends limiting intake of butter/margarine, cheese, red meat, pastries/sweets, and fried fast foods.
But it's not clear what effect this diet may have on age-related structural changes in the brain which are associated with neurodegenerative disease, such as Alzheimer's and Parkinson's diseases, explain the researchers.
To explore this further, they focused on 1647 middle aged and older adults (average age 60 at the start of the study) from the Framingham Heart Study Offspring cohort (FOS). All of them had regular health check ups every 4-8 years, with MRI brain scan assessments every 2-6 years from 1999 onwards.
They also completed at least 1 food frequency questionnaire (FFQ) at their check-ups between 1991-5, 1995-8, and/or 1998-2001 to assess dietary intake. And they had at least 2 brain MRI scan assessments between 1999 and 2019 with no evidence of a stroke or dementia by the time of their first MRI scan.
Their average MIND diet score was just under 7 out of a possible 15, where 15 indicates the highest level of adherence. Those in the top third of adherence were more likely to be women and college educated, and less likely to be current smokers or living with obesity.
And fewer of them had health issues likely to affect brain health, including type 2 diabetes, high blood pressure, and cardiovascular disease.
During an average monitoring period of 12 years, reductions in total brain, grey matter, white matter, and hippocampal volumes, alongside increased cerebrospinal fluid, ventricular volumes, and white matter hyperintensities-bright spots indicative of tissue damage-were evident on the MRI scans of all the participants.
But higher MIND diet scores were associated with slower grey matter shrinkage/loss. Each 3 point increase was associated with slower (0.279 cm³/year) loss, equivalent to 20% less age-related decline and 2.5 years of delayed brain ageing.
Similarly, each 3-point increase in MIND diet score was associated with slower expansion of total ventricular volume by −0.071 cm³/year, equivalent to 8% less tissue loss and 1 year of delayed brain ageing.
The primary dietary contributors to the observed beneficial associations included berries, which were associated with slower increases in ventricular volumes, and poultry, also associated with slower increases in ventricular volumes and a slower decline in grey matter.
On the other hand, higher intake of sweets was associated with faster ventricular expansion and hippocampal atrophy, while fried fast foods were also linked to a greater decline in hippocampal volume.
"MIND-recommended foods rich in antioxidants, such as berries,and high-quality protein sources like poultry may reduce oxidative stress and mitigate neuronal damage," suggest the researchers. "Conversely, fried fast foods, often high in unhealthy fats, trans fats, and advanced glycation end-products, may contribute to inflammation and vascular damage," they add.
Unexpectedly, higher whole grain intake was associated with unfavourable structural changes, including faster declines in grey matter and hippocampal volume, and faster ventricular expansion, while higher cheese intake was associated with slower reductions in grey matter and hippocampal volume and less ventricular enlargement and fewer bright spots.
The associations found were consistent across a series of further analyses and stronger in older participants, suggesting that this diet may be more beneficial in those at higher risk of faster brain ageing, or who exhibit larger variation in the rate of brain atrophy, say the researchers.
Stronger associations were also observed for those who were more physically active and who weren't overweight or obese, suggesting that combined lifestyle strategies might help to lower the risk of neurodegenerative disease, they add.
This is an observational study, and as such, no firm conclusions can be drawn about cause and effect, and the researchers acknowledge that food frequency questionnaires are subject to recall bias. And the researchers weren't able to exclude mild cognitive impairment at the time of the first MRI scan, changes in dietary habits over time, or genetic risk factors.
As the participants were predominantly White, the findings might not apply to other ethnicities, they point out.
Nevertheless, they conclude: "These findings reinforce the potential of the MIND diet as a brain-healthy dietary pattern and support its role in strategies aimed at slowing neurodegeneration in ageing populations."
