Autopsies Show Relationship Between Alzheimer’s Pathology and Diet in Older Adults

— Green leafy vegetable intake inversely correlated with pathology in postmortem brain tissue

by
Judy George, Deputy Managing Editor, MedPage Today
March 8, 2023

Healthy, plant-based dietary patterns were linked with less postmortem Alzheimer’s disease pathology, primarily beta-amyloid load, in older adults.

Both MIND diet scores (β -0.022, P=0.035; standardized beta -2.0) and Mediterranean diet scores (β -0.007, P=0.039; standardized beta -2.3) were significantly associated with lower global Alzheimer’s pathology, reported Puja Agarwal, PhD, of Rush University in Chicago, and co-authors.

MIND and Mediterranean diets were also associated with less beta-amyloid at autopsy (MIND standardized beta -2.0, Mediterranean standardized beta -2.9), the researchers wrote in Neurology.

People who had the highest intake of green leafy vegetables — 7 or more servings per week — had less global Alzheimer’s pathology than those who ate only 1 or 2 servings weekly (tertile 3 vs tertile 1: β -0.115, P=0.0038). None of the diet scores had an association with phosphorylated tau tangles.

The study assessed MIND and Mediterranean dietary patterns in 581 autopsied participants. Both diets are rich in nutrients and bioactive compounds and have antioxidant properties.

The Mediterranean diet recommends vegetables, fruit, and three or more servings of fish a week. The MIND diet prioritizes green leafy vegetables like spinach, kale, collard greens, and other vegetables, prioritizes berries over other fruit, and recommends one or more servings of fish a week. Both recommend small amounts of wine.

Associations between dietary patterns and Alzheimer’s pathology have been suggested in earlier work using imaging and cerebrospinal fluid biomarkers. “A large body of evidence links a healthy diet and nutritional intake with a lower risk of developing Alzheimer’s disease,” noted Lisa Mosconi, PhD, of Weill Cornell Medicine in New York City, who wasn’t involved with the study.

“This important study corroborates previous research by showing that elderly individuals following either a Mediterranean diet or MIND diet exhibit a lower burden of Alzheimer’s pathology in their brains,” Mosconi told MedPage Today. “Although more clinical trials are needed, recommending targeted dietary interventions is evidence-based and safe for reducing the risk of Alzheimer’s dementia.”

Agarwal and colleagues analyzed data from the longitudinal Rush Memory and Aging Project cohort, a prospective study of older adults who agreed to annual clinical evaluations and brain donation at death. They followed 581 people with a mean age of 84 at their first dietary assessment and a mean age of 91 at death. Participants completed annual food frequency questionnaires.

Mean follow-up was 6.8 years, and 73% of participants were women. Proximate to death, 38.5% of participants had a diagnosis of clinical dementia. At autopsy, 66% had a pathologic diagnosis of Alzheimer’s disease.

Mediterranean diet scores had 11 dietary components and ranged from 0 to 55. MIND diet scores had 15 components and ranged from 0 to 15. Mediterranean diet scores in the top tertile were an average of 35; in the bottom tertile they were 26. MIND diet scores in the top tertile were an average of 9.1; in the bottom tertile they were 5.9.

Autopsy data included beta-amyloid load, phosphorylated tau tangles, and global AD pathology (summarized neurofibrillary tangles, neuritic and diffuse plaques). Regression models controlled for age at death, sex, education, APOE4 status, and total calories. Findings persisted when adjusted further for physical activity, smoking, and vascular disease burden, and when participants with mild cognitive impairment or dementia were excluded.

“For clinical context, we calculated the ratio of the coefficients and found that a MIND diet score one point higher corresponded to typical plaque deposition of participants who are 4.25 years younger in age, with other characteristics being the same,” Agarwal and colleagues noted.

The study had several limitations, the researchers acknowledged. Its observational design limited the ability to establish causal relationships. In addition, participants were mostly white older adults; findings may not apply to younger people or to more diverse populations.