FOODS that stimulate “good bacteria” in the gut, including oats, berries, bananas, garlic, leeks and onions, could play a role in helping prevent Alzheimer’s disease, a major study suggests.

Scottish dementia experts have described as “exciting” new research which has shown for the first time there is a “indisputable” link between an imbalance in gut bacteria and the development of damaging amyloid plaques in the brain.

They found that proteins produced by certain intestinal bacteria, identified in the blood of patients, could modify the interaction between the immune and the nervous systems and trigger the disease.

It is already known that gut flora composition in patients with Alzheimer’s disease is altered, compared to people who do not suffer from such disorders. 

Their microbiota has a reduced diversity, with an over-representation of certain bacteria and a strong decrease in other microbes.

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Italian and Swiss scientists studied a cohort of older people between 65 and 85 years of age. 

Some suffered from Alzheimer’s disease or other neurodegenerative diseases causing similar memory problems, while others did not have any memory problems.

Using PET scans, researchers measured the amount of harmful plaques and then quantified the presence in their blood of various inflammation markers and 
proteins produced by intestinal bacteria.

High blood levels of lipopolysaccharides and certain short-chain fatty acids (acetate and valerate) were associated  with large amyloid deposits in the brain.  

Conversely, high levels of another short-chain fatty acid, butyrate, were associated with less amyloid pathology.

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Moira Marizzoni, of the Fatebenefratelli Center in Brescia, Italy, and lead author of the study, said: “Our results are indisputable: certain bacterial products of the intestinal microbiota are correlated with the quantity of amyloid plaques in the brain.”

Scientists say the discovery paves the way for potential protective strategies – through the administration of a “bacterial cocktail” for example, or of pre-biotics to feed the “good” bacteria in the intestine but cautioned that such interventions would have to be applied at a very early stage in the disease.

Professor Craig Ritchie, Professor of the Psychiatry of Ageing at the University of Edinburgh and Director of Brain Health Scotland, said: “This is an exciting avenue of enquiry that does make biological sense.” 

The body is full of trillions of bacteria, viruses and fungi, known collectively as the microbiome. While some bacteria are associated with disease, others are said to be important for the immune system, heart, weight and many other aspects of health.

Probiotics are the good bacteria while prebiotics are the good bacteria promoters. They work in synergy with each other to keep the gastrointestinal tract healthy.

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Both are available as supplements but can also be sourced through diet. Probiotic sources include sauerkraut.

Researchers from the University of Geneva have already proved a link between inflammation, certain intestinal bacteria and Alzheimer’s disease and wanted to study the interplay more closely.

Moira Marizzoni, of the Fatebenefratelli Center in Brescia, said: “High blood levels of lipopolysaccharides and certain short-chain fatty acids (acetate and valerate) were associated with large amyloid deposits in the brain.

“Conversely, high levels of another short-chain fatty acid, butyrate, were associated with less amyloid pathology.
“This work thus provides proof of an association between certain proteins of the gut microbiota  and cerebral amyloidosis through  a blood inflammatory phenomenon.”

Craig Ritchie, Professor of the Psychiatry of Ageing at the University of Edinburgh and Director of Brain Health Scotland, said the next step would be to confirm the findings in a larger cohort of patients.

He added: “This science is a few years away from any practical implications as much is still needed to be done and understood but this is certainly new evidence that provides further evidence between gastrointestinal and brain health.”

HeraldScotland:

The Herald’s Think Dementia Campaign aims to improve care, treatment and financial support for people affected by dementia and their families.