Memory decline is one of the biggest fears people face as they age. While Alzheimer’s disease and dementia remain complex conditions with no cure, new evidence suggests that supporting gut health could be a simple way to protect the brain.
Researchers at King’s College London tested a daily mix of prebiotic fiber and protein in older adults and found it improved memory in just 12 weeks. The findings, published in Nature Communications, highlight how everyday supplements may help keep the brain sharper for longer. Here, we’ll look at what the study uncovered and how prebiotics like inulin and fructooligosaccharides could protect cognitive health.
The supplement and what the study found
The trial enrolled 36 pairs of twins aged 60 and older. One twin in each pair received a prebiotic supplement containing inulin and fructooligosaccharides along with a modest protein shake, while the other received a placebo plus the same protein. Both groups were encouraged to perform light resistance exercises.
After three months, the twins who took the prebiotic scored higher on sensitive memory tests compared to their siblings. In particular, they made fewer mistakes on the paired associates learning (PAL) test, a measure often used to detect subtle changes linked to early Alzheimer’s disease. Lead researcher Dr. Mary Ni Lochlainn explained that these improvements were significant because they showed up in a relatively short time frame.
The supplement also changed the composition of the gut microbiome, increasing levels of Bifidobacterium, a beneficial genus known to thrive on inulin and fructooligosaccharides. These bacteria produce metabolites such as short-chain fatty acids that influence brain function through the gut-brain axis. This pathway involves immune signals, nerve communication, and hormones that connect digestive health with cognition.
Participants tolerated the supplement well, with only mild digestive complaints reported. Adherence to the daily routine was high, suggesting that prebiotics could be a practical option for older adults looking to support their memory.
What else to know before trying prebiotics
While the results are promising, the researchers caution that this was a small, short-term study. The trial included mostly healthy older women, so it does not tell us how people with dementia, more advanced memory decline, or different medical conditions might respond. Larger and longer studies are needed to confirm whether these early gains persist and whether they translate into fewer daily memory slips.
Experts also stress that supplements are just one piece of the puzzle. A balanced diet rich in fiber, regular exercise, good sleep, and social engagement all contribute to brain health. Since people respond differently based on their baseline microbiome and overall health, it’s best to check with a healthcare provider before starting a new supplement routine.
Still, the accessibility and affordability of prebiotic fibers make them an appealing candidate for further research. As Professor Claire Steves, senior author of the study, noted, these plant-based fibers are “cheap and available over the counter“, a rare combination when it comes to potential dementia prevention strategies.
The gut and brain are more connected than most of us realize. By feeding beneficial bacteria with prebiotic fibers, it may be possible to strengthen memory and reduce dementia risk. While it’s too early to call this a solution, the findings point to a safe, low-cost way to support cognitive health as we age.
