A major new review has found growing evidence that problems in the gut may be linked to memory loss and brain diseases like Alzheimer’s.
The study was done by scientists at the George Washington University School of Medicine and Health Sciences. They looked at 58 studies from different countries, all done on people (not animals), making this one of the most complete reviews so far.
The researchers focused on something called the “gut microbiome.” This is the name for all the bacteria and other tiny organisms that live in our digestive system. When the balance of these bacteria is off—a condition called dysbiosis—it may affect the whole body, including the brain.
Experts are still trying to understand why some people lose their memory or develop dementia. One area they are studying is the “gut-brain axis.” This is the way the gut, immune system, and brain talk to each other.
When the gut bacteria are not balanced, it may cause inflammation and harm brain cells. This could play a role in diseases like Alzheimer’s, which affects nearly 7 million people in the U.S. and around 50 million worldwide.
Across all the studies, people with mild memory problems or Alzheimer’s disease had different gut bacteria compared to healthy older adults. For example, people with Alzheimer’s had higher levels of certain bacteria groups called Pseudomonadota and Actinomycetota.
They also had less diversity in their gut bacteria, meaning fewer types of bacteria were present than in healthy people. This is important because a more diverse microbiome is usually a sign of better gut health.
The researchers also found that the types and amounts of gut bacteria changed between different stages of cognitive decline—from mild memory issues to full Alzheimer’s. In those with Alzheimer’s, their gut bacteria showed signs of working differently, including reduced activity in areas related to energy and immune system function.
Dr. Leigh Frame, the lead author of the study, said that these changes in gut bacteria might help explain how poor gut health could lead to brain inflammation and memory loss. She emphasized that while these findings are promising, more research is needed. Current studies mostly show a link but do not prove that one causes the other.
However, many scientists believe that improving gut health might be one way to protect the brain. Diets rich in fiber, fruits, vegetables, and whole grains are known to support a healthy gut. These foods may help reduce inflammation and support brain function over time.
Right now, clinical trials are underway to test if changing the gut microbiome can slow down or prevent memory problems. These trials are being done at George Washington University and other research centers around the world.
This new review adds to a growing body of research showing that the gut may play a bigger role in brain health than we once thought. If future studies confirm these early findings, it could open the door to new treatments for Alzheimer’s disease and other memory disorders.
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The study is published in Alzheimer’s & Dementia.
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