For many people in their 60s and 70s, those little memory slips feel all too familiar. You walk into a room and forget why you went there, or you lose the shopping list on the way to the store.
A new twin study from King’s College London suggests that a simple daily mix of protein and plant fiber might help soften some of those lapses in healthy older adults.
Researchers found that adults over 60 who took a combination of prebiotic fibers and protein powder for 12 weeks performed better on sensitive memory tests than their twins who received a placebo. Those tests included a visual paired associates learning task often used to spot early signs of Alzheimer’s disease, and the supplemented group made fewer errors overall.
How the trial worked
The PROMOTe trial enrolled 36 pairs of twins, 72 people in total, all at least 60 years old and on average in their early 70s. Within each pair, one twin was randomly assigned a daily prebiotic mix while the other received a look-alike placebo.
Everyone in the study also did simple resistance exercises at home and took a branched chain amino acid protein supplement, since the original goal was to test both muscle and brain outcomes at the same time.
The prebiotic group received about seven grams per day of two common fibers, inulin and fructooligosaccharides, which are already sold as over the counter supplements in many countries. After three months, chair rise times and other strength measures looked similar in both groups.
Memory scores were different though. When researchers combined several cognitive measures into a single factor, the prebiotic group showed a statistically significant improvement compared with their placebo twins.
Feeding the gut to nudge the brain
Prebiotics are non-digestible fibers that act as food for gut microbes. In this trial, stool samples showed that the supplement shifted the gut community, including an increase in Bifidobacterium, a bacterial genus often linked to healthier metabolism and brain function in earlier work.
Other recent studies report that lower levels of Bifidobacterium combined with higher levels of Akkermansia are tied to more severe multiple sclerosis, which hints that this microbe balance matters well beyond digestion.
The idea that the gut and brain talk to each other is not new, but evidence connecting the so-called gut brain axis to cognition keeps growing. Reviews now suggest that gut bacteria produce short chain fatty acids and other signaling molecules that can influence inflammation, mood, and learning over time.
What the experts say and what it does not prove
“We are excited to see these changes in just 12 weeks, which holds promise for brain health in our aging population,” said geriatrician Mary Ni Lochlainn, the study’s first author. Senior author Claire Steves noted that these plant fibers are cheap, available over the counter, and generally well tolerated, while stressing that larger, longer trials are still needed.
There are important caveats. The trial was small and most participants were women, so the findings may not apply equally to men or to people already living with dementia.
The main physical outcome, muscle function, did not improve over three months, and some volunteers reported mild bloating, which is a familiar trade off for anyone who has suddenly upped their fiber intake.
What this could mean for everyday life
For the most part, the results support a simple message. Looking after your gut might help your brain age a little more gracefully. That does not mean everyone should rush to buy a specific powder, or that prebiotics can prevent Alzheimer’s on their own.
Experts still point first to a balanced lifestyle that includes movement, sleep, social contact, and plenty of fiber-rich foods like vegetables, legumes, and whole grains.
With the global population of adults over 60 expected to pass two billion by mid-century, even modest cognitive benefits from low-cost supplements could matter a great deal, especially for people worried about staying independent and keeping on top of daily tasks.
At the end of the day, what this study really offers is a proof of concept that the microbiome is a realistic target for brain health, not just a buzzword.
The study was published in Nature Communications.
