Editor's note: This popular story from the Daily Briefing's archives was republished on June 13, 2023.

People who closely followed the Mediterranean or MIND diets were less likely to have signs of Alzheimer's in their brain tissue, according to a  study published in  Neurology.

Study details and key findings

For the study, researchers examined brain tissue from 581 individuals who donated their bodies to the "Memory and Aging Project" at Rush University. Diet information was collected starting from 2014 for an average of six to seven years.

This dietary information was then compared to the number of sticky beta-amyloid plaques and tau tangles — both classic signs of Alzheimer's —in each person's brain at autopsy.

Overall, the researchers found that people who followed the Mediterranean diet or the closely related Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet had fewer amyloid plaques and tau tangles than those who ate other types of diets.

According to CNN, the Mediterranean diet focuses primarily on plant-based cooking, and meals should largely focus on fruits and vegetables, whole grains, beans and seeds, and some nuts. While fish is considered a staple, eggs, dairy, and poultry are eaten in smaller portions, and meat is rarely used.

The MIND diet, which was developed in 2015 by Rush researchers, combines both the Mediterranean diet and the DASH (Dietary Approaches to Stop Hypertension) diet and has a particular focus on brain health. People are recommended to eat dark, leafy greens every day, and berries should be eaten at least five days a week.

According to the researchers, people who followed either of the two diets had "almost 40% lower odds" of having enough plaques or tangles to be diagnosed with Alzheimer's.

In addition, the brains of people who most closely adhered to the Mediterranean diet "had average plaque and tangle amounts in their brains similar to being 18 years younger" than those who did not adhere to the diet. For those on the MIND diet, the average plaque and tangle amount was similar to being 12 years younger.

Even people who followed these two diets "moderately well" saw benefits, reducing their risk of Alzheimer's by around a third, according to the researchers.

The researchers also found that simple dietary changes could reduce amyloid buildup in the brain. For example, adding just one food category from either the Mediterranean or MIND diets, such as more fruits or vegetables, reduced amyloid buildup to a level that was similar to being around four years younger.

When looking at specific dietary components, leafy greens provided the most benefits, and people who ate the largest amounts of leafy green vegetables a week had plaque amounts that were equal to being 19 years younger than those who ate the smallest amounts. Other healthy foods, such as berries and whole grains, also provided benefits.

"Doing a simple dietary modification, such as adding more greens, berries, whole grains, olive oil and fish, can actually delay your onset of Alzheimer's disease or reduce your risk of dementia when you’re growing old," said Puja Agarwal, an assistant professor of internal medicine at the Rush University Medical Center and the study's lead author.

Commentary

According to Heather Snyder, VP of medical and scientific relations at the Alzheimer's Association, the study's findings are "intriguing" and take "what we know about the link between nutrition and risk for cognitive decline a step further by looking at the specific brain changes that occur in Alzheimer's disease."

Although the most effective diet for health is still unclear, Snyder said that people should aim to have a "heart-healthy diet that incorporates nutrients that our bodies and brains need to be at their best."

Other health experts have expressed similar sentiments. "While this study doesn't definitively prove that it's possible to slow brain aging through dietary choices, the data are compelling enough for me to add green leafy vegetables to most of my meals, and to suggest the Mediterranean-style diet for my patients at risk,” said Richard Isaacson, a preventive neurologist at the Institute for Neurodegenerative Diseases of Florida.

Rudy Tanzi, a professor of neurology at Harvard Medical School, said since the Mediterranean diet is also heart healthy, it can also reduce the risk of "or stroke and neurovascular injury that can also increase risk for Alzheimer's disease pathology."

"What's good for the heart is good for the brain," Tanzi added.

In the future, the researchers hope to conduct additional studies to further their understanding of dietary behavior and Alzheimer's disease, including what foods could impact amyloid plaques or tau tangles more effectively.

"We still need to really tease apart what exactly is happening," Agarwal said. "But overall, these diets are rich in the essential nutrients and bioactives which reduce overall inflammation and oxidative stress in the brain and probably leading up to less accumulation of amyloid plaques and tangles." (LaMotte, CNN, 3/8; Mitchell, New York Post, 3/9; Moniuszko, CBS News, 3/9; HealthDay/U.S. News & World Report, 3/9; Agarwal et al., Neurology, 3/8)