Alzheimer’s Pathology Linked to Diet
by Judy George for MedPage Today:
People who followed a Mediterranean-style diet closely had less amyloid and tau pathology, increased brain volume in regions vulnerable to Alzheimer's disease, and better memory performance, a cross-sectional analysis in Germany showed.
Higher adherence to a Mediterranean type of diet was linked to larger mediotemporal gray matter volume, better memory scores, and lower pathological levels of biomarkers for amyloid plaques and tau tangles, reported Tommaso Ballarini, PhD, of the German Center for Neurodegenerative Diseases (DZNE) in Bonn, and co-authors.
Mediotemporal volume mediated the association between diet and memory. Diet adherence favorably moderated links between amyloid beta (Aβ42/40 ratio), phosphorylated tau 181 (p-tau181), and mediotemporal atrophy, they wrote in Neurology.Earlier research showed that a Mediterranean diet -- high in fish, vegetables, fruits, and nuts; low in meat and dairy products -- may be linked to a reduced risk for cognitive impairment and fewer early signs of Alzheimer's disease.
"We combined several types of data to better understand this protective effect of the diet," Ballarini said. The findings suggest that following a Mediterranean type of diet might mitigate the associations between these factors, Ballarini observed. "This made us hypothesize that eating a Mediterranean-like diet might act like a brake against Alzheimer's progression," he told MedPage Today.
"We need all the tools we can get to slow or even prevent Alzheimer's disease and its cousins," noted Vijay Ramanan, MD, PhD, of the Mayo Clinic in Rochester, Minnesota, who wasn't involved with the study. "It is heartening to see the growing literature supporting lifestyle modifications -- including a Mediterranean-style diet, healthy sleep, and cognitive, physical, and social activity -- as important pillars to promote brain health," Ramanan told MedPage Today.
"These factors will remain crucial as we continue to develop multi-pronged treatment approaches for these devastating degenerative brain diseases."In their study, Ballarini and colleagues looked at 512 people from the DZNE Longitudinal Cognitive Impairment and Dementia (DELCODE) study with a mean age of about 70. Of those, 169 people were cognitively normal, while 343 had a high risk of developing Alzheimer's disease (53 had relatives with Alzheimer's, 209 had subjective cognitive decline, and 81 had mild cognitive impairment). A subsample of 226 people had cerebrospinal fluid (CSF) assessments of Alzheimer's biomarkers.
The researchers used a German adaptation of the semi-quantitative EPIC food frequency questionnaire (EPIC-FFQ) to evaluate diet. Scores on the EPIC-FFQ could span from 0 to 9, with higher scores reflecting better adherence to a Mediterranean diet.Participants earned a score of 1 when their food intake was equal or above the sex-specific median for six food categories (fish, vegetables, fruits/nuts, legumes, cereals, and higher ratio of monounsaturated/saturated fats) or below the cutoff for foods not typical of a Mediterranean diet (meat, dairy products). Moderate alcohol consumption (10-50 g/day in men and 5-25 g/day in women) was considered beneficial and scored 1 point.Better adherence to a Mediterranean-like diet was linked to:
A significant positive association with brain gray matter volume in the right parahippocampal gyrus and right hippocampus
Better memory (β=0.03 ± 0.02, P=0.038), after adjusting for age, sex, education, BMI, caloric intake, and physical activity
CSF measures of p-tau181 (β=-1.96±0.68, P=0.004) and Aβ42/40 ratio (β=0.003 ± 0.001, P=0.008)
Each 1 point decline on the EPIC-FFQ corresponded to nearly 1 year of brain aging, the researchers noted. Results were consistent after correcting for APOE4 status.
An exploratory analysis of individual diet components suggested a beneficial connection between monounsaturated/saturated fat ratio and p-tau181 and Aβ42/40.
A limitation of the study is that the sample was enriched for Alzheimer's risk, which means the findings may not apply to the general population. Food intake was self-reported and assessed at only one point in time, though data have shown that dietary patterns tend to be stable for years among older adults, the researchers noted."
Although these observational findings are promising and help generate new hypotheses, a causal interpretation should be avoided," Ballarini said. "Replication studies and an extension to longitudinal data will be needed confirm these results and to clarify the mechanisms by which diet might influence the dynamic progression of Alzheimer's disease and cognitive performance in late life."