THURSDAY, May 6, 2021 (HealthDay News) -- A diet rich in vegetables, fruits, olive oil and fish -- the so-called Mediterranean diet -- may protect the brain from plaque buildup and shrinkage, a new study suggests.
Researchers in Germany looked at the link between diet and the proteins amyloid and tau, which are a hallmark of Alzheimer's but are also found in the brains of older people without dementia.
"These results contribute to the body of evidence that links eating habits with brain health and cognitive performance in old age," said lead researcher Tommaso Ballarini, a postdoctoral researcher from the German Center for Neurodegenerative Diseases in Bonn.
Eating a Mediterranean-like diet might protect the brain from neurodegeneration and therefore reduce the risk of developing dementia, he said.
"However, further research is needed to validate these findings and to better understand the underlying mechanisms," Ballarini said, since this study could not prove a cause-and-effect relationship.
For the study, he and his colleagues collected data on more than 500 people, of whom more than 300 had a high risk for Alzheimer's disease. The participants reported their diets and took tests of language, memory and executive function. They also underwent brain scans, and more than 200 had spinal fluid samples taken to look for biomarkers of amyloid and tau.
After adjusting for age, sex and education, the researchers found that each point lower on the Mediterranean diet scale was linked to nearly one year more of brain aging, seen in the part of the brain closely tied with Alzheimer's disease.
People who didn't follow a Mediterranean diet had higher levels of markers of amyloid and tau, the researchers found. Also, people who didn't follow a Mediterranean diet scored lower on memory tests than those who did.
"Overall, a closer adherence to a Mediterranean-like diet was associated with a preserved brain volume in regions vulnerable to Alzheimer's disease, fewer abnormal amyloid and tau and better performance on memory tests," Ballarini said.
One limitation of the study is that people self-reported their diet, which could lead to errors in recalling what and how much they ate, the researchers noted.
One U.S. expert said diet is only one aspect in the Alzheimer's picture.
"We continue to see literature revolve around nutrition and diet and what it might mean in later life," said Heather Snyder, vice president for medical and scientific relations at the Alzheimer's Association.
Diet, however, isn't the only lifestyle factor that might lower the risk for Alzheimer's disease, she said.
"I think the data continues to evolve and demonstrate that lifestyle interventions are likely beneficial for reducing cognitive decline," Snyder said.
Other lifestyle components, such as exercise, are also important, she said. It's not clear yet how diet and exercise reduce the risk of Alzheimer's disease.
"I think the key is to really understand what that recipe is, because it's unlikely to be any one thing," Snyder said. "It's more likely going to be a combination and the synergy of those behaviors that is most beneficial."
Snyder noted that these same lifestyle factors help reduce the risk of cardiovascular disease and even some cancers. "But there is the need to tease out how and what might be the most beneficial for each of those," she added.
"When we look at Alzheimer's and cognition and cognitive decline, we have consistently seen diets like the Mediterranean diet are associated with lower risk in later life. What they all have in common is that a balanced diet makes sure your brain has the nutrients that it needs," Snyder said.
"I think what we know is what's good for your heart is good for your brain, so eat a balanced diet," she said. "There's no one right diet, but make sure you get all the nutrients you need, but also get active, get moving and stay engaged."
The report was published online May 5 in the journal Neurology.
For more on Alzheimer's disease and diet, see the Alzheimer's Association.
SOURCES: Tommaso Ballarini, PhD, German Center for Neurodegenerative Diseases, Bonn, Germany; Heather Snyder, PhD, vice president, medical and scientific relations, Alzheimer's Association; Neurology, May 5, 2021, online