While nutrition studies pose a unique set of challenges, experts say there is a growing body of compelling evidence that suggests certain diets may benefit an aging brain. Writing for the New York Times, Amelia Nierenberg explains the connection between diet and brain health.

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4 elements of a 'brain-boosting' diet

Scientists still do not know exactly what causes Alzheimer's—the most common form of dementia—and there is currently no medication on the market that can reverse the disease, said Uma Naidoo, the director of nutritional and metabolic psychiatry at Massachusetts General Hospital.

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"But," Naidoo said, "we can impact how we eat."

Research suggests that individuals who have certain conditions, including heart disease, high blood pressure, obesity, and diabetes, are more likely to experience age-related cognitive decline. Further, the risks of developing those conditions can also be increased with poor diet and exercise habits, Naidoo explained, which suggests there are steps people can take to decrease the chances of developing dementia.

To better understand the link between dementia and diet, Nierenberg spoke with two dozen researchers who identified four key elements of a "brain-boosting" diet.

Leafy greens

According to Naidoo, one significant change you can implement is to "up your plant game" with leafy greens rich in nutrients and fiber, which have been linked to slower age-related cognitive decline.

In a recent randomized controlled trial conducted in Israel, researchers performed brain scans on over 200 people who had been divided into three diet groups. After 18 months, they found those who followed a "green" Mediterranean diet experienced the slowest rate of age-related brain atrophy, followed closely by those who adhered to a traditional Mediterranean diet. However, participants who followed regular healthy diet guidelines—less plant-based, with more processed food and red meat compared with the other two diets—experienced higher declines in brain volume.

Colorful fruits and vegetables

In an observational study from 2021, researchers tracked over 77,000 people for around 20 years. According to the researchers, those with diets high in flavonoids were less likely to experience signs of age-related cognitive decline compared with those who consumed fewer flavonoids.

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In particular, the MIND diet signals that berries, which are rich in fiber and antioxidants, provide cognitive benefits. 

"I don't think there are miracle foods, but, of course, it's really good to eat the fruits and vegetables," said Allison Reiss, a member of the medical, scientific, and memory screening advisory board at the Alzheimer's Foundation of America.

Fish

According to Nierenberg, "[m]any types of seafood, in particular fatty fish, are good sources of omega-3 fatty acids, which have been long associated with better brain health and reduced risk of age-related dementia or cognitive decline."

"Fish is brain food," said Mitchel Kling, director of the memory assessment program at the New Jersey Institute for Successful Aging at the Rowan University School of Osteopathic Medicine.

In particular, a specific omega-3 fatty acid, called docosahexaenoic acid (DHA) found in cold-water, fatty fish, such as salmon, is "the most prevalent brain fat," said Lisa Mosconi, the director of the Alzheimer's Prevention Program at Weill Cornell Medicine.

Our bodies are not capable of making enough DHA on their own, according to Mosconi. "We have to provide it from the diet, which is a strong argument toward eating fish."

According to Walter Willett, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health, two to three servings each week will provide "virtually all the benefit."

Nuts, whole grains, legumes, and olive oil

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"Nuts and seeds have been repeatedly linked to slower cognitive decline," Nierenberg writes.

In a 2021 review of 22 studies on nut consumption involving almost 44,000 people, researchers discovered that individuals with a high risk of cognitive decline tended to see improved outcomes when they increased their nut consumption, specifically walnuts.

In addition, whole grains and legumes, including lentils and soybeans, "also appear to have benefits for heart health and cognitive function," Nierenberg adds. In a 2017 study of over 200 people in Italy aged 65 and older, researchers discovered a link between consuming three servings of legumes each week and better cognitive performance.

Meanwhile, a 2022 study of over 92,000 U.S. adults found that higher consumption of olive oil was linked to a 29% reduction in risk of dying from neurodegenerative disease.

Dietary supplements may not have a significant impact on brain health

According to the experts Nierenberg spoke with, "there is little to no evidence that dietary supplements — including fatty acids, vitamin B or vitamin E — will reduce cognitive decline or dementia."

"Supplements cannot replace a healthy diet," Mosconi said.

In a study of roughly 3,500 older adults, researchers determined that omega-3 supplements—often marketed for their ability to support brain health—did not slow cognitive decline.

According to Willett, when it comes to supplements like fish oil, you don't need to "load up like a seal."

Instead, Ronald Petersen, the director of the Mayo Clinic Alzheimer's Disease Research Center, advised people to follow this advice: "If it comes from a plant, eat it. If it's made in a plant, don't eat it." (Nierenberg, New York Times, 4/21)