In Alzheimer's disease, neurons in the brain die. Largely responsible for
the death of neurons are certain protein deposits in the brains of affected
individuals: So-called beta-amyloid proteins, which form clumps (plaques)
between neurons, and tau proteins, which stick together the inside of
neurons. The causes of these deposits are as yet unclear. In addition, a
rapidly progressive atrophy, i.e. a shrinking of the brain volume, can be
observed in affected persons. Alzheimer's symptoms such as memory loss,
disorientation, agitation and challenging behavior are the consequences.
Scientists at the DZNE led by Prof. Michael Wagner, head of a research group
at the DZNE and senior psychologist at the memory clinic of the University
Hospital Bonn, have now found in a study that a regular Mediterranean-like
dietary pattern with relatively more intake of vegetables, legumes, fruit,
cereals, fish and monounsaturated fatty acids, such as from olive oil, may
protect against protein deposits in the brain and brain atrophy. This diet
has a low intake of dairy products, red meat and saturated fatty acids.
A nationwide study
A total of 512 subjects with an average age of around seventy years took
part in the study. 169 of them were cognitively healthy, while 343 were
identified as having a higher risk of developing Alzheimer's disease - due
to subjective memory impairment, mild cognitive impairment that is the
precursor to dementia, or first-degree relationship with patients diagnosed
with Alzheimer's disease. The nutrition study was funded by the
Diet-Body-Brain competence cluster of the German Federal Ministry of
Education and Research (BMBF) and took place as part of the so-called
DELCODE study of the DZNE, which does nationwide research on the early phase
of Alzheimer's disease - that period before pronounced symptoms appear.
"People in the second half of life have constant eating habits. We analyzed
whether the study participants regularly eat a Mediterranean diet - and
whether this might have an impact on brain health ", said Prof. Michael
Wagner. The participants first filled out a questionnaire in which they
indicated which portions of 148 different foods they had eaten in the past
months. Those who frequently ate healthy foods typical of the Mediterranean
diet, such as fish, vegetables and fruit, and only occasionally consumed
foods such as red meat, scored highly on a scale.
An extensive test series
The scientists then investigated brain atrophy: they performed brain scans
with magnetic resonance imaging (MRI) scanners to determine brain volume. In
addition, all subjects underwent various neuropsychological tests in which
cognitive abilities such as memory functions were examined. The research
team also looked at biomarker levels (measured values) for amyloid beta
proteins and tau proteins in the so-called cerebrospinal fluid (CSF) of 226
subjects.
The researchers, led by Michael Wagner, found that those who ate an
unhealthy diet had more pathological levels of these biomarkers in the
cerebrospinal fluid than those who regularly ate a Mediterranean-like diet.
In the memory tests, the participants who did not adhere to the
Mediterranean diet also performed worse than those who regularly ate fish
and vegetables. "There was also a significant positive correlation between a
closer adherence to a Mediterranean-like diet and a higher volume of the
hippocampus. The hippocampus is an area of the brain that is considered the
control center of memory. It shrinks early and severely in Alzheimer's
disease," explained Tommaso Ballarini, PhD, postdoctoral fellow in Michael
Wagner's research group and lead author of the study.
Continuation of nutrition study is planned
"It is possible that the Mediterranean diet protects the brain from protein
deposits and brain atrophy that can cause memory loss and dementia. Our
study hints at this," Ballarini said. "But the biological mechanism
underlying this will have to be clarified in future studies." As a next
step, Ballarini and Wagner now plan to re-examine the same study
participants in four to five years to explore how their nutrition -
Mediterranean-like or unhealthy - affects brain aging over time.
Reference:
Ballarini T, Lent DM van, Brunner J, et al. Mediterranean diet, alzheimer
disease biomarkers and brain atrophy in old age. Neurology. 2021. doi:
10.1212/WNL.0000000000012067
Tags:
Biology & Health