How Gut Bacteria Affect Aging and Cognition

By Simon Spichak, Reporter at Being Patient

The human body is host to trillions of microscopic organisms — collectively called the microbiome — that shape our health across the lifespan. This exciting field of research provides a new approach to understanding and treating cognitive decline and dementia. Unlike the genetic code stored within each of our cells, the microbiome community can be changed easily through diet and other lifestyle factors like exercise. But as we change the microbes in our gut, how do these changes affect the aging brain?

Over millennia, microorganisms co-evolved with humans to form a beneficial working relationship: Our body provides room and board so that microbes digest the foods that our body cannot. After digesting these foods, the byproducts of this process — biological molecules — can exchange signals with different cells within the human body.

During birth, the infant is exposed to their first set of microbes, which make their way to the gastrointestinal tract, and play formative roles in immune, gut, and nervous system development. As an infant develops and grows, the community of microorganisms within the gut stabilizes into a healthy ecosystem. But as the body ages, this ecosystem begins to destabilize. Around this time, many older adults may experience cognitive decline or various forms of dementia. Researchers still don’t know the relationship between our brain health and our gut microbiome. Studies are underway now, searching for answers as to why the composition of this microbial community is different in dementia, and whether changes in the microbiome actually cause changes in cognitive function. 

A Microbiome-Based Treatment for Alzheimer’s

Shanghai Green Valley pharmaceuticals have developed the first microbiome-based therapeutic for Alzheimer’s disease, with promising results in mild to moderate Alzheimer’s in China. In 2020, it received approval from the FDA for testing in the USA. The drug, sodium oligomannate, is an extract made from seaweed and kelp, food for gut bacteria. 

According to studies in humans, the gut bacteria digest this food, initiating a domino effect within the ecosystem — including alterations in the microbiome, peripheral immune cells, and neuroinflammation. It is akin to introducing more native flowers for pollinators in a forest; this one small change can make the ecosystem a little healthier. 

In sodium oligomannate’s Phase 3 trial conducted in China, the drug led to cognitive improvements over 36 weeks. It was also well-tolerated and did not cause significant side effects. 

Whether or not further trials show this drug is effective, it provides a blueprint for developing new gut microbiome-based therapeutics for mild to moderate cognitive impairment and dementia. 

While sodium oligomannate is not yet approved for use by the FDA, there are other ways to promote a healthy gut — and possibly in turn, a healthier brain.

Feeding the Gut Microbiome

While the multi-billion-dollar probiotics market would have us believe otherwise, there isn’t a single secret pill or superfood that will supercharge the microbes in your gut. Instead, healthier food choices, such as the Mediterranean diet, have been found to improve both the health of the gut microbiome and cognition in older populations. Several studies found that eating a healthy Mediterranean diet — which is rich in fruits, vegetables, legumes, nuts, seeds, and fish — reduced the risk of developing mild cognitive impairment or dementia.  

You might also be wondering about the rows upon rows of products with beneficial microbes, marked probiotics, on the shelves of your grocery store or pharmacy. Many products in the U.S. are inadequately labeled and may not adhere to the definition of a probiotic, making it unclear whether the bacteria survive the stomach acid and reach the gut. In the E.U., probiotic labeling is a lot stricter — requiring evidence that a certain amount of ingested bacteria confers a beneficial effect. 

Instead of probiotics, experts recommend looking towards transitioning to a Mediterranean diet. Other ways to maintain a healthy microbiome include reducing levels of stress and exercising regularly. While there aren’t any approved gut microbiome therapeutics yet, research proves all of these microbiome-friendly lifestyle choices will help you and your microbes age healthily. In the meantime, microbiome scientists are hard at work developing potential new microbiome treatments for Alzheimer’s and dementia.


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Melissa Belardo, APRN

Clinical Investigator

Melissa Belardo, is a certified family nurse practitioner (FNP-BC), joins K2 Medical Research with more than a decade of clinical experience. She has served as an investigator in over 20 trials. Prior to clinical research, she held roles in gastroenterology, hepatology, and nurse education.

Melissa’s academic background includes a Bachelor of Science in Nursing from Adventist University, followed by a master’s degree in Family Nurse Practitioner from Georgetown University.

Melissa is a native of the US Virgin Islands’ and is fluent in both English and Spanish; Melissa has lived in central Florida for the past twenty years. When she’s not at work, you can find her volunteering at her local church and spending time with family.