For those with Alzheimer's disease, there's a tell-tale sign in the brain. Amyloid plaques and neurofibrillary tangles appear as an early signal of what's to come.
But recent research has shown that these physical changes to the brain may not be the sole drivers of the disease, and that something as simple as diet could change our cognitive resilience to dementia in the future.
The specific diet – called the MIND diet – is based on the Mediterranean diet and the Dietary Approaches to Stop Hypertension (DASH) diet (in fact, MIND is short for 'Mediterranean-DASH diet Intervention for Neurodegenerative Delay'). It was developed by a team of nutritional epidemiologists at Rush University; previously, a 2015 study demonstrated its potential benefits.
Since then, many researchers and the general public have been placing a focus on this dietary approach as a potential Alzheimer's prevention strategy.
Study after study has shown that following the MIND diet by eating more leafy veggies, other vegetables, berries, nuts, olive oil, whole grains and fish provides at least some protection from cognitive decline.
Now, a long-term study from the same team at Rush University in Illinois has found that participants who followed the MIND diet – even moderately – had better cognitive functioning later in life, independent of any amyloid plaques or neurofibrillary tangles they may have had.
"Some people have enough plaques and tangles in their brains to have a post-mortem diagnosis of Alzheimer's disease, but they do not develop clinical dementia in their lifetime," says geriatric health researcher Klodian Dhana from Rush Medical College.
"Some have the ability to maintain cognitive function despite the accumulation of these pathologies in the brain, and our study suggests that the MIND diet is associated with better cognitive functions independently of brain pathologies related to Alzheimer's disease."
The researchers analyzed data on 569 participants who had died during a long-term study started in 1997, called the Memory and Aging Project. Each of the participants agreed to undergo yearly clinical evaluations while they were alive, plus an autopsy after death.
In 2004, the researchers started giving the participants a questionnaire about what types of foods they were eating; for this new study, the team used these dietary data to retroactively give the patients a score of how close to the MIND diet they had been.
The results were promising, finding that a higher MIND diet score was associated with better cognitive functioning prior to death. That was the case even when adjusting for those that had no cognitive impairment when the research started, or those diagnosed with Alzheimer's in a post mortem due to the presence of amyloid plaques and neurofibrillary tangles.
Obviously, this study has some limitations. The diet was self-reported by the participants, which can be inaccurate in a general population, let alone one with cognitive decline.
"We explored this concern by excluding from analysis participants whose first global cognitive evaluation was in the lowest 25 percent of the sample. We also calculated the cumulative average of the MIND diet score across follow-up to limit measurement error," the team explains in their new paper.
"Another limitation is that the study sample is composed of mostly white volunteers who agreed to annual evaluations and post-mortem organ donation, thus limiting generalizability."
However, this is a large long-term study, and shows at the very least that this dietary approach is worth exploring further. Plus, it probably can't hurt to eat more leafy green veggies and other whole foods.
"The diet seemed to have a protective capacity and may contribute to cognitive resilience in the elderly." Dhana says.
"Diet changes can impact cognitive functioning and risk of dementia, for better or worse … There are fairly simple diet and lifestyle changes a person could make that may help to slow cognitive decline with aging, and contribute to brain health."
The research has been published in the Journal of Alzheimer's Disease.