The Gut–Brain Connection: How Your Microbiome May Protect Your Brain as You Age
Many people worry about their brain health as they get older, about memory loss, brain fog, or even the risk of diseases like Alzheimer’s or Parkinson’s. What’s often overlooked is that one of the most powerful influences on your brain may be happening quietly in your gut microbiome.
Gut Microbiome and Brain Health: How the Gut Talks to the Brain
Your gut is home to trillions of microbes that send constant signals to your brain. These signals include nutrients, neurotransmitters, and proteins that affect how your nervous system functions. This two-way street is called the gut–brain axis.
When your gut is balanced, these signals tend to be calming and protective. But when the gut ecosystem is disrupted (dysbiosis), the signals can become inflammatory, stressful, and, as new research suggests, even harmful for brain proteins themselves.
Gut Microbiome and Neurodegeneration
Most people have heard of the gut–brain connection in IBS and IBD, where stress, mood, and gut symptoms feed into each other. That work focuses on how the microbiome influences digestion, sensitivity, and mood regulation.
While I was recently in Spain, I came across the work of Dr. Natalia Sánchez de Groot (Autonomous University of Barcelona). Her research is shining a light on a very different side of the gut–brain connection. She and her colleagues are uncovering that some gut bacteria can produce proteins that act a bit like prions.
Prions are proteins that can misfold and then encourage other proteins to misfold, a process linked with diseases like Alzheimer’s and Parkinson’s.These microbial proteins may “whisper” to our own, nudging them into harmful shapes. In other words, the microbiome might influence the very first steps of dementia and neurodegeneration.
Why Diet Matters More Than Ever
This is where your food choices become critical. A gut that lacks fibre and plant diversity often loses its protective species and becomes dominated by inflammatory bacteria. These microbes produce endotoxins like LPS, degrade the gut lining, and may amplify harmful protein signals.
High-protein, high-fat, low-fibre diets (like strict paleo or carnivore) can tip the balance toward exactly this kind of dysbiosis.
On the other hand, a diverse, plant-rich diet provides the raw materials your gut microbes need to protect you:
Fibre fuels butyrate producers → Butyrate is an anti-inflammatory molecule that strengthens the gut lining and calms immune over activation, supporting long-term cognitive health.
Polyphenols feed protective microbes → Found in richly coloured plants (berries, pomegranates, olives, green tea, walnuts, etc)., polyphenols encourage anti-inflammatory bacteria and shield brain cells from damage.
Resistant starches build resilience → Foods like healthy whole grains (quinoa, rye, oats and whole wheat) and green bananas nurture microbes that restore the gut barrier and protect against “leaky gut” brain inflammation.
The more variety, the better. Studies consistently show that eating 30-40+ different plant foods per week is linked with greater microbial diversity and resilience as well as lower risk of cognitive decline. The more variety, the better. Studies consistently show that eating diverse plant foods is linked with greater microbial diversity and resilience as well as lower risk of cognitive decline.
What About the Carnivore Diet and Neuroinflammation?
You may have seen headlines or social media stories suggesting that carnivore or ketogenic diets can reduce neuroinflammation and improve brain health. And it’s true: there is some early evidence that being in ketosis, the metabolic state these diets create, can calm overactive immune cells in the brain, reduce oxidative stress, and improve mitochondrial function in animal models of Alzheimer’s and Parkinson’s.
There are even small case series and pilot studies suggesting people with neurological or inflammatory conditions may feel better on very low-carb diets.
But here’s the important context:
Most of this research is animal or cell-based, not large human trials.
The human studies we do have are very small, short-term, and uncontrolled. This is low quality evidence.
The long-term effects of eliminating fibre and polyphenol-rich plant foods are unknown, and potentially harmful.
Meanwhile, we have decades of robust evidence that diets rich in fibre, resistant starch, and polyphenols improve microbial diversity, reduce systemic inflammation, and protect against dementia and cognitive decline.
So while ketosis may provide short-term symptom relief for some, relying solely on animal foods may come at the cost of losing the very microbial allies that help protect your gut and brain in the long run.
Protecting Your Gut Barrier to Reduce Neuroinflammation
You can’t change your genes. But you can change your gut environment. That means you can influence the signals reaching your brain every day.
Here’s where to start:
Build diversity: choose a wide range of vegetables, fruits, legumes, nuts, and seeds.
Include daily fibre and resistant starch: oats, beans, lentils, cooled rice or potatoes.
Prioritise polyphenols: berries, pomegranates, walnuts, green tea, olives.
Support your gut barrier: nutrients like glutamine and zinc carnosine, or herbs like marshmallow root, can protect the intestinal lining.
Reduce animal protein, saturated fat and ultra-processed foods: they feed inflammatory microbes and may increase LPS-related neuroinflammation.
Gut Health and Alzheimer’s, Dementia, and Aging Brains
Your gut isn’t just about digestion, it’s a frontline for brain health. Research by Dr. Sánchez de Groot and others is showing us that certain gut bacteria may play a role in the earliest stages of neurodegeneration by producing prion-like proteins.
The hopeful message is this: by eating more plants, fibres, and polyphenol-rich foods, and by protecting your gut lining, you’re not only caring for your digestion, you’re investing in your brain’s future and supporting your health span.
