One study suggests that molecules found in fish and other seafood may play a role in protecting and improving cognitive function in the brain.
The researchers investigated the role of trimethylamine N-oxide (TMAO), which is present in people’s diets, and is produced by the body during the digestion of fish.
It is broken down by bacteria in the gut as foods containing TMAO are ingested.
Researchers say the breakdown product is carried into the bloodstream and converted back into TMAO, which interacts with organs throughout the body.
The circulatory and vascular systems of the brain are exposed to TMAO, which interacts directly with the blood–brain barrier.
This work is a major step toward better understanding how our diet can positively affect cognitive function and healthy aging.
This barrier prevents potentially harmful toxins in the body from reaching the brain.
However, as people age, the blood-brain barrier leaks out and is more easily penetrated by these toxins.
They found in the new study that TMAO makes the blood-brain barrier less leaky.
According to the research, the long-term presence of TMAO in the diet positively affected both blood-brain barrier integrity and cognition in rats—preventing recognition memory loss—compared to the absence of the molecule.
Researchers from Nottingham Trent University and Queen Mary University of London argue that the findings have implications for dietary interventions in humans that target the gut-brain connection to potentially improve cognitive function.
Professor Leslie Hoyles, a microbiologist at Nottingham’s School of Science and Technology, said: “This work is a major step forward in better understanding how our diet can positively affect cognitive function and healthy aging.”
She adds: “Microbiota-produced metabolites come from gut bacteria and have many effects on our bodies.
“We have shown that TMAO – a bacterial metabolite associated with the human gut microbiome and found in high amounts in fish and seafood – has a direct and beneficial interaction with the blood–brain barrier and affects cognitive function.
“This opens up many new works exploring dietary interventions linking the gut and brain.”
Lead author Dr Simon MacArthur, from the Institute of Dentistry, Queen Mary University of London, said: “We know that damage to the blood vessels of the brain is a feature of many neurological diseases, including stroke and dementia.
“By identifying gut bacteria capable of modifying brain blood vessel integrity, our findings open up exciting new avenues for protective interventions by manipulating diet.
“We’ve known for a long time that eating fish is good for your brain—now we can add gut bacteria to this old adage as a new aspect.”
The study is published in the journal Microbiome.