What is good for your aging gut may also be good for your aging brain. A landmark study in twins found that daily prebiotic supplements improve memory scores in people over 60. Moreover, these supplements are inexpensive and widely available — making this discovery especially promising for public health.
What the Study Found
Researchers at King’s College London conducted a double-blind trial using two affordable plant-fiber prebiotics. Specifically, they tested inulin and fructooligosaccharide (FOS). Both supplements are available over the counter in many countries.
After just 12 weeks, participants who consumed the supplements scored higher on cognitive tests. Importantly, scientists use the same visual memory and learning test to detect early signs of Alzheimer’s disease. Therefore, these results carry significant weight in the field of brain health research.
How the Twin Trial Worked
The study enrolled 36 pairs of twins — all aged 60 or above. Researchers randomly split each pair. One twin received a daily prebiotic mixed into protein powder, while the other received a placebo powder. Crucially, neither twin knew which supplement they consumed.
Twin studies hold particular value in scientific research. They help scientists separate the effects of genetics from those of environment. As a result, findings from such trials carry greater statistical reliability. King’s College London hosts the United Kingdom’s largest adult twin registry, adding further credibility to this work.
Inulin and FOS: What Are They?
- Inulin is a dietary fiber from the fructan class, found naturally in chicory root and garlic.
- FOS (Fructooligosaccharide) is a plant carbohydrate that producers commonly use as a low-calorie natural sweetener.
Both supplements are affordable and safe for regular consumption. Additionally, both mix easily into everyday foods or drinks, making them practical choices for older adults.
The Gut-Brain Connection Explained
Prebiotics are non-digestible plant fibers that feed beneficial bacteria living in the gut. Scientists increasingly refer to the gut as the body’s “second brain” — and for good reason. The gut contains its own extensive nervous system, which communicates constantly with the brain through what researchers call the gut-brain axis.
Interestingly, evidence linking gut health to brain function grows stronger every year. High-fiber supplements like inulin and FOS nourish the colon’s microbiome. Consequently, they allow “good” bacteria to thrive and multiply. This bacterial activity, in turn, appears to influence cognitive performance in measurable ways.
What Bifidobacterium Does for the Brain
After 12 weeks, twins who consumed prebiotic supplements showed noticeably higher levels of Bifidobacterium in their gut. This finding is significant. Studies on mice suggest that Bifidobacterium actively reduces cognitive deficits by regulating gut-brain connections.
“We are excited to see these changes in just 12 weeks,” said Mary Ni Lochlainn, a geriatric medicine researcher at King’s College London. “This holds huge promise for enhancing brain health and memory in our aging population.”
Furthermore, geriatrician Claire Steves at King’s College London highlighted the practical advantages of these supplements. “These plant fibers are cheap and available over the counter. They are also safe and acceptable,” she said. “Our next task is to see whether these effects last over longer periods and in larger groups.”
Limitations and Next Steps
Study Limitations
The trial had a relatively small sample of 36 twin pairs. Additionally, the participant group skewed mostly female. Although researchers adjusted for sex differences, some selection bias may remain within King’s College London’s twin cohort.
However, this limitation opens an important conversation. Women develop Alzheimer’s disease at twice the rate of men. Therefore, studying female-majority groups may provide more relevant insights into cognitive decline prevention. Notably, the supplements did not produce significant physical benefits — muscle loss in aging participants did not improve despite the role inulin and FOS play in musculoskeletal health.
What Comes Next
Researchers plan to test whether cognitive benefits persist over longer periods. They also aim to run larger trials with more diverse participants. These follow-up studies will clarify whether prebiotics can become a mainstream strategy for supporting brain health in older populations.
Why This Matters for Aging Adults
Cognitive decline affects millions of older adults around the world. Currently, few affordable and accessible tools exist to slow this process. However, this study suggests that a simple daily supplement could make a meaningful difference.
Cost is a particularly compelling factor. Unlike many pharmaceutical interventions, inulin and FOS require no prescription and are widely available at low prices. As a result, they could benefit a broad population — especially in communities with limited healthcare access.
Beyond memory, a healthy gut microbiome connects to outcomes across multiple conditions, including multiple sclerosis, Parkinson’s disease, and obesity. Feeding the gut the right fibers may, therefore, open pathways to treating a wide range of illnesses.
