Sandee LaMotte, CNN for CNN Health

People who consumed foods from the plant-based Mediterranean and brain-focused MIND diets had fewer of the hallmark signs of Alzheimer’s — sticky beta-amyloid plaques and tau tangles in the brain — when autopsied, a new study found.

The MIND diet is short for Mediterranean-DASH Diet Intervention for Neurodegenerative Delay.

In fact, people who most closely followed either of the diets had “almost 40% lower odds” of having enough plaques and tangles in brain tissue to be diagnosed with Alzheimer’s, according to the study.

“People who scored highest for adhering to the Mediterranean diet had average plaque and tangle amounts in their brains similar to being 18 years younger than people who scored lowest,” according to a statement on the study.  “Researchers also found people who scored highest for adhering to the MIND diet had average plaque and tangle amounts similar to being 12 years younger than those who scored lowest.”

That’s not all. Adding just one food category from either diet — such as eating recommended amounts of vegetables or fruits — reduced amyloid buildup in the brain to a level similar to being about four years younger, the study said.

“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 study author Puja Agarwal, an assistant professor of internal medicine at the Rush University Medical Center in Chicago.

The most benefit is from leafy greens, she said.  However adding more berries, whole grains and other healthy foods recommended by the diets was also beneficial, she said.

“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 Alzheimer’s disease researcher Dr. Richard Isaacson, a preventive neurologist at the Institute for Neurodegenerative Diseases of Florida. He was not involved in the new study.

“Of course, the Mediterranean diet is also heart healthy … by reducing the risk for stroke and neurovascular injury that can also increase risk for Alzheimer’s disease pathology,” said Rudy Tanzi, a professor of neurology at Harvard Medical School, who was not involved in the study.

“What is good for the heart is good for the brain,” said Tanzi, who is also the director of the genetics and aging research unit at Massachusetts General Hospital in Boston.

The MIND diet was developed in 2015 by Rush researchers interested in taking the Mediterranean diet to the next level by focusing it on brain health. Instead of providing a blanket statement — eat more vegetables and fruits — as the Mediterranean diet does, the MIND diet recommends specific amounts of known brain-healthy foods, Agarwal said.

Inside the MIND Diet

For example, leafy greens, the darker the better, should be eaten every day of the week on the MIND diet.  Those include arugula, collards, dandelion greens, endive, grape leaves, kale, mustard greens, romaine lettuce, spinach, Swiss chard and turnip greens.

Berries are also stressed over other fruits on the MIND diet.  Blackberries, blueberries, raspberries or strawberries should be eaten at least five days a week.

A 2017 study of nearly 6,000 healthy older Americans with an average age of 68 found those who followed the Mediterranean or MIND diet lowered their risk of dementia by one-third.