Researchers are testing whether special plant fibers called prebiotics can protect memory in older adults with early signs of cognitive decline. A new randomized controlled trial of 164 people aged 60-79 will take prebiotic supplements for 26 weeks while researchers measure brain activity and memory using brain scans and cognitive tests. The theory is that prebiotics feed beneficial gut bacteria, which produce protective chemicals that communicate with the brain through the microbiota-gut-brain axis, potentially slowing memory loss before dementia develops.
Scientists are testing whether special types of fiber called prebiotics can help protect the brain and memory in older adults who are starting to notice small memory problems. According to Gram Research analysis, this new study involves 164 people aged 60-79 who will take prebiotic supplements for six months while researchers measure changes in brain activity and thinking skills. The research focuses on how gut bacteria might communicate with the brain through a pathway called the microbiota-gut-brain axis. If successful, this could lead to a simple, food-based way to prevent memory loss and dementia before serious problems develop.
Key Statistics
A 2026 randomized controlled trial published in Frontiers in Nutrition is recruiting 164 older adults aged 60-79 with early memory concerns to test whether 26 weeks of prebiotic supplementation improves brain function measured by functional MRI brain scans during memory tasks.
The PRECODE trial is testing three types of prebiotics—chicory inulin, resistant dextrin, and seaweed polysaccharide—against placebo in people with subjective cognitive decline plus additional lifestyle risk factors for Alzheimer’s disease, with results expected to guide new prevention strategies for dementia.
According to Gram Research analysis, cognitive disorders like dementia are projected to triple by 2050, making early intervention in people with subjective cognitive decline an urgent priority, which is why researchers are testing whether prebiotics targeting the microbiota-gut-brain axis can prevent accelerated cognitive decline.
The Quick Take
- What they studied: Whether special plant fibers (prebiotics) can improve brain function and memory in older adults who are experiencing early signs of memory problems
- Who participated: 164 people between ages 60-79 who have noticed some memory changes and have other risk factors for brain decline, recruited for a 26-week study
- Key finding: This is a new study just beginning, so results aren’t available yet. Researchers will measure brain activity using brain scans and memory tests to see if prebiotics help
- What it means for you: If the study shows positive results, eating more prebiotic-rich foods (like chicory, certain starches, and seaweed) might become a simple way to protect your brain as you age. However, we need to wait for the results before making any changes
The Research Details
PRECODE is a carefully designed experiment where 164 older adults are randomly divided into groups. Some groups receive different types of prebiotic fiber supplements (chicory inulin, resistant dextrin, and seaweed polysaccharide), while others receive a placebo (a fake supplement that looks identical). Neither the participants nor the researchers know who gets the real supplement versus the fake one—this is called “double-blinded” and helps prevent bias. The study lasts 26 weeks, and participants will have brain scans and memory tests at the beginning and end to measure any changes.
The researchers chose this approach because they want to understand how gut bacteria might protect the brain. Your gut contains trillions of bacteria that produce special chemicals called short-chain fatty acids and tryptophan-indoles. These chemicals may send signals to your brain through a pathway scientists call the microbiota-gut-brain axis. Prebiotics are special plant fibers that feed the good bacteria in your gut, helping them produce more of these protective chemicals.
The study focuses on people with subjective cognitive decline (SCD+), which means they’ve noticed their memory isn’t quite as sharp as it used to be, but they don’t have diagnosed dementia yet. This is an ideal time to test prevention strategies, before serious memory problems develop.
This research approach is important because it tests a prevention strategy before people develop serious memory loss. Current treatments for Alzheimer’s disease are limited, so finding ways to prevent it early is crucial. By using brain imaging (fMRI) to measure actual brain activity during memory tasks, researchers can see if prebiotics change how the brain works, not just whether people remember things better. This gives us deeper insight into the mechanism—the ‘how’ and ‘why’ behind any benefits.
This is a high-quality study design because it uses randomization (random assignment to groups), blinding (neither participants nor researchers know who gets the real supplement), and a placebo control group (for fair comparison). The study measures multiple outcomes including brain imaging, memory tests, gut health markers, and immune function, giving a complete picture. However, this is a relatively small study (164 people), and results won’t be available until the study is completed. The study is registered on ClinicalTrials.gov, which means it follows strict scientific standards.
What the Results Show
This study is currently ongoing and results are not yet available. The primary outcome being measured is brain activation during memory tasks using functional MRI (fMRI) brain scans, specifically looking at how the brain responds during a working memory test called the 2-back task. Researchers will compare brain activity between people who received prebiotics and those who received placebo to see if the supplements change how efficiently the brain works during memory challenges.
When results are published, they will show whether 26 weeks of prebiotic supplementation actually changes brain function in people with early memory concerns. The brain scans will reveal if prebiotics help the brain use less energy to complete memory tasks (a sign of better efficiency) or if they activate different brain regions involved in memory and thinking.
Beyond brain scans, researchers are also measuring traditional memory and thinking tests using a battery of neuropsychological assessments. They’re examining gut health markers to see if prebiotics actually change the composition of gut bacteria and the levels of protective chemicals they produce. The study also tracks immune system markers and metabolic factors (like blood sugar and cholesterol), since these are connected to both gut health and brain function. These secondary outcomes will help explain the ‘why’ behind any brain changes observed.
This research builds on growing evidence that gut bacteria influence brain health through the microbiota-gut-brain axis. Previous studies have shown that people with dementia have different gut bacteria than healthy people, and that certain bacterial metabolites protect brain cells. However, most previous research has been observational (watching what happens naturally) rather than testing whether changing the gut bacteria actually prevents cognitive decline. PRECODE is one of the first rigorous trials to test whether prebiotics can prevent memory loss in people at risk, making it an important next step in translating laboratory findings into practical prevention strategies.
This study has several limitations to keep in mind. First, it’s relatively small (164 people), so results may not apply to everyone. Second, it only lasts 26 weeks, so we won’t know if benefits last longer or if they continue after stopping the supplements. Third, the study focuses on people aged 60-79 with specific risk factors, so results may not apply to younger people or those without these risk factors. Fourth, we don’t yet know if the prebiotic supplements will actually work—this is an experimental study, not proven treatment. Finally, the study measures brain activity during one specific memory task, which may not capture all aspects of thinking and memory.
The Bottom Line
Wait for study results before making major changes. However, eating more prebiotic-rich foods (like chicory root, asparagus, garlic, onions, and seaweed) is generally healthy and safe for most people, so you could gradually increase these foods in your diet now. If you have concerns about memory loss, talk to your doctor about screening and prevention strategies. Do not rely on supplements alone—maintaining a healthy lifestyle with exercise, sleep, social connection, and a Mediterranean-style diet remains the strongest evidence-based approach to brain health. Confidence level: Moderate (based on emerging research, not yet proven in this specific trial).
This research is most relevant to people aged 60 and older who have noticed subtle memory changes or have risk factors for cognitive decline (like high blood pressure, diabetes, or family history of dementia). It’s also important for healthcare providers looking for new prevention strategies. People with diagnosed dementia or Alzheimer’s disease should not rely on this as a treatment. Younger people without memory concerns may not see the same benefits, though maintaining gut health is beneficial for everyone.
If the study shows positive results, benefits would likely take weeks to months to appear, since the study measures changes over 26 weeks. Real-world benefits might take even longer. Don’t expect immediate improvements in memory—brain health changes happen gradually. If you start eating more prebiotic foods, give it at least 8-12 weeks before assessing any effects on energy, digestion, or thinking.
Frequently Asked Questions
Can prebiotics really help prevent memory loss and dementia?
Prebiotics show promise based on laboratory research showing gut bacteria produce brain-protective chemicals, but human evidence is still emerging. The PRECODE trial will provide the first rigorous test in people with early memory concerns. Results aren’t available yet, so prebiotics aren’t proven to prevent dementia, though eating prebiotic-rich foods is generally healthy.
What are prebiotics and where can I find them in food?
Prebiotics are plant fibers that feed beneficial gut bacteria. Common food sources include chicory root, asparagus, garlic, onions, leeks, bananas, oats, legumes (beans and lentils), and seaweed. Unlike probiotics (live bacteria), prebiotics are the food that helps your existing gut bacteria thrive and produce protective compounds.
How does the gut-brain axis work and why does it matter for memory?
Your gut bacteria produce chemicals called short-chain fatty acids and tryptophan-indoles that travel through your bloodstream and cross into your brain, influencing inflammation, nerve cell health, and brain function. An imbalanced gut microbiota is associated with cognitive decline, so improving gut health through prebiotics may protect memory and thinking skills.
Who should consider taking prebiotic supplements right now?
Most people should focus on eating prebiotic-rich foods rather than supplements, since food provides additional nutrients. People aged 60+ with memory concerns or family history of dementia might discuss prebiotic supplementation with their doctor, but wait for PRECODE results before starting. Maintain proven brain-healthy habits like exercise, sleep, and Mediterranean diet first.
How long does it take to see benefits from prebiotics?
The PRECODE study measures changes over 26 weeks, suggesting benefits take months to appear. Real-world effects might take 8-12 weeks or longer. Don’t expect immediate memory improvements—brain health changes gradually. Some people notice improved digestion within days, but cognitive benefits require sustained dietary changes.
Want to Apply This Research?
- Track daily prebiotic food intake (servings of chicory, asparagus, garlic, onions, seaweed, legumes) and weekly subjective memory performance (rate your memory on a 1-10 scale for specific tasks like remembering names, appointments, or shopping lists without writing them down)
- Gradually increase prebiotic-rich foods by adding one new source per week: Week 1 add garlic to meals, Week 2 add onions, Week 3 add asparagus, Week 4 add legumes. Track which foods you enjoy and which improve digestion. Set a goal of 5+ servings of prebiotic foods daily
- Use the app to log prebiotic foods daily and rate memory performance weekly using the same memory challenges (like remembering a shopping list or recalling what you did yesterday). After 8-12 weeks, review trends to see if increased prebiotic intake correlates with subjective memory improvements. Also track digestive comfort, since prebiotics can initially cause bloating
This article describes a clinical trial that is currently ongoing with results not yet available. The findings discussed are theoretical and based on the study design, not proven outcomes. Prebiotics are not a cure or proven treatment for dementia or cognitive decline. Anyone concerned about memory loss should consult with a healthcare provider for proper evaluation and diagnosis. This information is for educational purposes only and should not replace professional medical advice. Do not start prebiotic supplements without discussing with your doctor, especially if you take medications or have digestive conditions. Prebiotic foods can cause bloating or gas in some people, particularly when first introduced.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.