A large new study, representing nearly a quarter million people, adds to a mountain of evidence showing that Mediterranean and DASH-style diets boost brain health. The analysis, published May 3 in JAMA Psychiatry, found that adults ages 45 and up who stuck to an eating plan high in green leafy vegetables, fruits, beans, nuts, and fish had a lower risk of dementia than those who didn’t follow such an eating plan.
The MIND diet (Mediterranean-DASH intervention for neurodegenerative delay) is a hybrid of the Mediterranean and DASH (dietary approaches to stop hypertension) diets. Both have been associated with a reduced risk of cardiovascular conditions like hypertension, heart attack, and stroke, as well as slower cognitive decline.
“The prevention of all-cause dementia is important, as it poses substantial burdens on healthcare systems and threatens the well-being of older adults, and lack of effective treatments makes its prevention crucial,” says the study author Changzheng Yuan, ScD, who works within the school of public health at Zhejiang University School of Medicine in Hangzhou, China.
“The MIND diet emphasizes natural plant-based foods, limited intake of certain animal foods and foods high in saturated fat, and encourages consumption of berries and green leafy vegetables rich in vitamins and antioxidants. The MIND diet has previously been associated with lower risk of Alzheimer's disease and slower cognitive decline.”
What the MIND Diet Study Found
For this analysis, Dr. Yuan and her colleagues examined medical data on more than 242,000 participants from a total of 14 studies. Participants ranged in age from 45 to 80 and older. Just over 6,000 were identified as having dementia.
Doctors use a number of tests to diagnose dementia, including cognitive and neuropsychological tests, brain scans, and lab tests.
Assessment of food intake was based on one or more food frequency questionnaires, which asked study subjects how often on average they consumed a specified amount of food in the past year. The questions provided details on the recommended and restricted food groups they were eating.
The researchers concluded that the better a person followed the MIND diet, the lower their dementia risk would be. The highest adherence was associated with about a 17 percent lower risk of dementia than the lowest adherence.
It’s important to note, Yuan says, that smoking may counteract the positive effects of the MIND diet. The diet was not significantly associated with reduced dementia risk among smokers, but in nonsmokers the beneficial relation was “strong and significant,” she says.
Keep These Foods in MIND
The MIND diet emphasizes natural plant-based foods and limits intake of animal protein and foods high in saturated fat. The diet also encourages consumption of leafy greens (such as kale and spinach) and berries (such as blueberries and strawberries), which are all rich in vitamins and antioxidants. Other recommended MIND food groups are nuts, olive oil, whole grains, fish, beans, and poultry.
Christine Ryan, RDN, a registered dietitian-nutritionist in Seattle, notes that berries are loaded with anthocyanidins and anthocyanins, pigments found in plants that may have antidiabetic, anticancer, anti-inflammatory, antimicrobial, and anti-obesity effects.
“Those dark, rich colors found in things like blueberries, blackberries, cranberries, and elderberries are key to getting rid of those reactive oxygen species [unstable molecules that can damage cells],” says Ryan.
Sticking to a MIND diet also means avoiding five food groups:
- Butter and margarine
- Cheese
- Red meat and products
- Fast food and other fried foods
- Pastries and sweets
“They are high in saturated fat and added sugar, which might be harmful for the human brain,” says Yuan.
The study authors underscore that recommended MIND diet foods may offer protection against brain aging through their antioxidant and anti-inflammatory properties, which can reduce inflammation and oxidative stress, a process that leads to cell and tissue damage.
In particular, the researchers say certain vitamins and nutrients found in these foods — such as vitamin E, folate, flavonoids, and carotenoids — have been shown to inhibit buildup of beta-amyloid protein, which is associated with Alzheimer's disease. On the other hand, red and processed meat contains compounds that may induce oxidative stress and inflammation and contribute to the development of dementia.
“With dementia, your blood vessels in your brain may not be getting enough oxygen, and this type of diet may improve that,” says Ryan, who was not involved in the study.
The MIND Diet May Reduce Harmful Plaques and Tangles
For Puja Agarwal, PhD, an assistant professor in the Alzheimer’s disease center at Rush University Medical Center in Chicago, the findings correspond with research she and her colleagues published March 8 in the journal Neurology. Her study involved about 600 people with an average age of 84 who agreed to donate their brains at death to advance research on dementia. Before their deaths, they completed dietary questionnaires.
Compared with those who didn’t follow a MIND-style diet, those who did had fewer amyloid plaques and tangles (signs of Alzheimer’s disease) in their brains.
“Their brains were similar to [those of people] almost four years younger,” says Dr. Agarwal, who was not involved in the new research. “These foods may help maintain brain function and to deal with plaques and tangles. Following the MIND and Mediterranean diets may be one way that people can improve their brain health and protect cognition as they age.”
Yuan cautioned that the research was limited by its observational nature, which cannot establish causal relationships. The study also relied on self-reported dietary data, which is not always accurate. She added that future studies should evaluate and identify the optimal intervention window for dementia prevention.
“Given the irreversible nature of neurodegeneration in the aging process, starting a healthy lifestyle — including a healthy diet — at an early life stage is essential for the prevention of neurodegenerative diseases in later life,” she says.