Study: Two diets reduced signs of Alzheimer's in brain tissue
Sign up for CNN’s Eat, But Better: Mediterranean Style. Our eight-part guide shows you a delicious expert-backed eating lifestyle that will boost your health for life.
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 Mediterranean diet focuses on plant-based cooking. The majority of each meal should be fruits and vegetables, whole grains, beans and seeds, along with a few nuts. There is a heavy emphasis on extra-virgin olive oil. Butter and other fats are consumed rarely, if at all. Sweets and goods made from refined sugar or flour are rare.
Meat can make a rare appearance but usually only to flavor a dish. Instead, meals may include eggs, dairy and poultry, but in much smaller portions than in the traditional Western diet. However, fish, which are full of brain-boosting omega-3’s, are a staple.
The Mediterranean diet, which has earned top honors as best diet for years, has an impressive list of science behind it. Studies have found this way of eating can prevent cognitive decline, but also help the heart, reduce diabetes, prevent bone loss, encourage weight loss and more.
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.
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.
The study, published Wednesday in the journal Neurology, examined the brains of 581 people who each donated their body as part of the Memory and Aging Project at Rush University. The project, which began in 1997, has been collecting yearly diet information on participants since 2004, Agarwal said.
The current study analyzed diet data from 2014, for an average of six to seven years, and then compared that information with the number of plaques and tangles in each person’s brain at autopsy.
Looking at brain tissue to determine the specific level of dementia markers was a unique part of the study, Agarwal said: “Previous studies with dementia risk were more on the clinical outcome — cognitive performance over time — but our study is actually looking at the specific hallmarks of disease in the brain after death.”
People who ate greater amounts of pastries, sweets, and fried and fast foods had much higher levels of plaques and tangles in their brain tissue, the study found.
Which food was the most helpful in reducing buildup? Green leafy vegetables, which are packed with bioactives, chemicals in foods that reduce inflammation and promote health. Examples of bioactive compounds include vitamins, minerals, flavonoids (antioxidants) and carotenoids (pigments in the skin of vegetables).
The brain tissue of people who ate the most leafy greens looked nearly 19 years younger in plaque buildup when compared with those who ate one or fewer servings per week, a statement on the study said.
“The combination of different nutrients and bioactives in green leafy vegetables make them unique,” Agarwal said. “They are very rich in many bioactives, flavonoids and lutein, which is important for brain health.”
There are different hypothesis on why lutein might be helping with the overall integrity of the brain,” she added, “such as reducing oxidative stress and inflammation.”
The most impressive impact of the diets was on beta-amyloid buildup, not tangles, and “the inverse association with beta-amyloid load was stronger for the Mediterranean diet than for the MIND diet,” the study said.
There was some reduction in tau tangles, the other key marker of Alzheimer’s, but it was not as robust as that for amyloid, Agarwal said. However, Agarwai and her team conducted another study that found that eating berries, a key part of the MIND diet, was helpful in reducing tangles in the brain.
“We still need to really tease apart what exactly is happening,” she 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.”