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What role might gut bacteria play in Alzheimer’s? Image credit: Westend61/Getty Images.
  • Studies have suggested that the health of a person’s gut microbiome can affect their overall health.
  • Previous research has also shown a correlation between gut health and diseases like Alzheimer’s disease and other types of dementia.
  • Researchers from the University of Nevada, Las Vegas have identified 10 specific types of bacteria in the gut associated with the likelihood of developing Alzheimer’s disease.

Over the past few years, we have learned more about how the health of the gut microbiome affects a person’s overall health.

Previous studies show having the proper amount of good bacteria in the gut helps with proper nutrient absorption and keeping the body’s immune system healthy.

Additionally, research suggests a well-balanced gut microbiome may help ward off diseases such as inflammatory bowel disease, Crohn’s disease, and ulcerative colitis.

And other studies show there may even be a correlation between gut health and diseases like cardiovascular disease, diabetes, obesity, and neurodegenerative diseases such as Alzheimer’s disease and other types of dementia.

Now, researchers from the University of Nevada, Las Vegas have identified 10 specific types of bacteria in the gut associated with the likelihood of developing Alzheimer’s disease.

Researchers hope their findings will eventually lead to new treatments to help lower an individual’s risk of developing the disease.

This study was recently published in the journal Scientific Reports.

The gut microbiome consists of literally trillions of microscopic organisms living in the body’s intestinal tract. These microorganisms consist of bacteria, fungi, viruses, and other organisms that assist with:

  • nutrient absorption from food
  • breaking down fiber
  • recovering energy from food metabolism
  • keeping the gut safe from diseases.

Every person’s gut microbiome is different. What is in it depends on a person’s diet, genetics, medication use, and their surrounding environment.

Signs of an unhealthy gut microbiome include:

Thankfully, there are a number of ways you can improve your35 gut microbiome, including:

According to Dr. Jingchun Chen, associate research professor at the University of Nevada, Las Vegas, and the lead researcher of this study, most people are surprised that their gut bacteria could affect their mood, their behaviors, and brain functions, but the evidence is mounting, and researchers are building an understanding of how gut bacteria and the health of the brain are connected.

“The gut microbiome could modulate brain function and behavior via the microbiota-gut-brain axis (MGBA) — a bidirectional communication system connecting neural, immune, endocrine, and metabolic pathways,” she explained to Medical News Today.

“For example, studies have shown that changes in the gut bacteria can affect the immune system, leading to chronic inflammation throughout the body, including the brain. This inflammation is thought to play a role in the development of various neurodegenerative diseases, including Alzheimer’s disease,” the researcher told us.

“Additionally, it has been suggested that some species of bacteria inhabiting the gut microbiome produce chemicals that can cross the blood-brain barrier and affect brain function. These chemicals, or metabolites, can work as neurotransmitters and interact with the nervous system and influence various processes, including cognition, mood, and behavior.”

– Dr. Jingchun Chen

Furthermore, Dr. Chen said, the gut microbiome is involved in the production of short-chain fatty acids (SCFAs), which have been shown to have anti-inflammatory effects on the brain.

“SCFAs can also affect the levels of certain hormones and neurotransmitters in the brain, which may play a role in the development of neurodegenerative diseases,” she added.

In this study, Dr. Chen and her team examined a large set of genetic data from the MiBioGen consortium initiative, which researchers said is the largest, multi-ethnic genome-wide meta-analysis of the gut microbiome to date.

At the conclusion of their research, scientists identified 10 specific types of gut bacteria associated with a likelihood of developing Alzheimer’s disease.

Six bacteria categories were identified as protective:

And four bacteria types were identified as risk factors for Alzheimer’s disease:

“In general, when the balance of gut bacteria is disrupted, it can lead to inflammation and immune dysfunction in the gut and throughout the body,” Dr. Chen explained. “This, in turn, can contribute to chronic inflammation in the brain, which is a hallmark of Alzheimer’s disease. For example, the Collinsella genus, a risk genus among the 10 Alzheimer’s disease-associated bacteria, has been found to produce more pro-inflammatory molecules.”

Dr. Chen said some studies have also suggested that specific types of gut bacteria may produce chemicals or proteins that can directly impact the brain and contribute to the development of Alzheimer’s disease.

“Overall, gut bacteria cause their effects by stimulating the central nervous system, immune system, and metabolite system, or even interacting with Alzheimer’s disease risk genes, such as theAPOE gene,” she added. “Much more needs to be learned about the specific mechanisms by which gut bacteria may contribute to this disease.”

Dr. Chen said the identification of a potential link between gut bacteria and Alzheimer’s disease has opened up new avenues for research into the prevention and treatment of this devastating disease.

“If researchers can understand the mechanisms by which gut bacteria contribute to the development of Alzheimer’s disease, it may be possible to develop new therapies that target these mechanisms,” she continued.

And Dr. Chen said these findings can be used by doctors in the future to highlight the importance of maintaining a healthy gut microbiome for overall health and well-being, including brain health.

“By educating patients about the importance of maintaining a healthy gut microbiome, doctors may be able to help prevent or delay the onset of Alzheimer’s disease and other neurodegenerative conditions,” she added.

After reviewing this study, Dr. David Merrill, a geriatric psychiatrist and director of the Pacific Neuroscience Institute’s Pacific Brain Health Center in Santa Monica, CA, not involved in the research, told MNT this is an important area of study to detail the potential connections between the gut microbiome and risk for dementia.

“We now know that dementia risk can be modified through changes in diet and lifestyle-related behaviors, so it would make sense to target those lifestyle changes in a way that helps promote a healthy gut microbiome,” he explained. “If we learn what constitutes a lower dementia risk microbiome, then we might try to target achieving that gut microbiome makeup and in an effort to actually decrease dementia risk.”

MNT also spoke with Dr. Clifford Segil, a neurologist at Providence Saint John’s Health Center in Santa Monica, CA, about this study. He was not involved in the research.

He said that while it was interesting to see the list of 10 specific bacteria teased out of hundreds normally living inside the gut, it still remains challenging to say how a diet is going to change the concentration of those 10 bacteria.

“In the year 2023, I’m not aware of a diet that can be changed to increase or decrease the concentration of the 10 proposed microorganisms,” Dr. Segil explained. “For example, I don’t know what you can eat to increase the concentration of one of their proposed preventative bacteria, Eisenbergiella. Or what you can eat to decrease the concentration of one of their proposed risk factor bacteria Collinsella.”

However, he said this research does speak to the importance of an overall healthy diet for keeping a person’s brain healthy.

“A healthy diet is going to lower sugars, it’s going to keep you not obese, and these kinds of things are great for general health,” Dr. Segil added. “If your general health is good, your brain health should be better, too.”