A randomized twin study revealed that a daily intake of protein mixed with prebiotics enhanced performance on a sensitive memory assessment after a 12-week period.
Researchers have been exploring how the gut microbiome interacts with the brain, utilizing immune, neural, and hormonal pathways to influence cognitive function throughout life.
This broader context is crucial when considering if nurturing gut bacteria can improve memory as we age.
The lead researcher, Mary Ni Lochlainn from King’s College London, along with her team, investigated whether incorporating a daily prebiotic alongside a moderate protein supplement and light resistance exercises could influence cognition in older twins.
In the study, 36 pairs of twins, all aged 60 or above, were enrolled. One twin was given inulin and fructooligosaccharides, while the other received a placebo, all conducted under double-blind conditions.
Both twins received the same branched-chain amino acid protein powder along with simple strength exercises they could do at home.
The 12-week program was conducted remotely, using video conferencing, online surveys, and mailed kits for cognitive assessments and stool sample analysis.
By choosing a twin study design, researchers minimized genetic and early environmental influences, making it more likely that differences observed between the twins reflected the effects of the supplements rather than shared familial habits.
What changed in the gut
Prebiotics are components of food that our enzymes cannot digest; bacteria in our gut ferment these components.
This study observed changes in levels of certain microbes, notably an increase in Bifidobacterium, which often responds positively to inulin and fructooligosaccharides in controlled studies.
Participants tolerated the supplement well, experiencing only mild and expected gastrointestinal discomfort. Adherence to the regimen remained high throughout the three months.
While the gut microbiota experienced some shifts, overall diversity remained stable. A few specific taxa did change in ways that biologically made sense in relation to fiber fermentation.
The group receiving prebiotics scored better on a combined cognition factor and committed fewer errors on the PAL test, which assesses visual paired associations and is sensitive to early signs of Alzheimer’s. This aligns with previous work suggesting that PAL can detect subtle memory issues earlier than many standard clinical scales.
“We are thrilled to witness these improvements in just 12 weeks. This presents a significant opportunity for enhancing brain health and memory in our aging population,” remarked Dr. Lochlainn.
The significance of the improvement in test scores lies in the ability to establish new links between locations and patterns, a fundamental skill that tends to deteriorate early in Alzheimer’s. Hence, even minor improvements in this area are noteworthy for individuals over 60.
What did not change
The supplement did not enhance chair rise time or other muscle strength indicators over the 12-week period, even though participants were provided with protein and encouraged to engage in simple exercise routines.
Short intervention periods often struggle to produce noticeable improvements in physical outcomes for older adults. The researchers recognized that the duration might have been too brief to effect muscle remodeling, although it was sufficient to initiate cognitive changes.
“These plant fibers are affordable and readily available over the counter, potentially benefiting a broad audience, especially during these economically challenging times. They are also safe and well-accepted,” noted Professor Claire Steves, a senior author from King’s College London. She emphasized the need for larger and longer trials in the future.
Gut-brain link fits the data
Gut bacteria produce short-chain fatty acids, neurotransmitter precursors, and other metabolites that communicate along nerves and through the immune system. Research indicates this axis plays a crucial role in learning and memory, particularly as we age.
Aging alters the makeup of microbial communities and the barriers that typically control inflammation, and these changes can impact brain circuits involved in attention, processing speed, and memory consolidation.
Fiber-fermenting organisms like Bifidobacterium thrive on inulin and fructooligosaccharides, generating metabolites associated with synaptic plasticity.
This biochemical understanding sheds light on why cognitive improvement occurred while physical metrics did not in the span of the three-month trial.
How to read these results
This randomized controlled trial utilized a robust within-family comparison, a clear intervention, and validated cognitive outcomes. It also kept participants involved through a completely remote design, making it easier for older volunteers to participate.
However, the study cohort was relatively small and predominantly female. Additionally, the findings primarily pertain to healthy older adults rather than individuals with diagnosed dementia.
While cognitive improvements were statistically significant, the study wasn’t geared towards assessing changes in daily functioning in a measurable way.
Diet, medications, and baseline microbiomes vary significantly among individuals; therefore, responses to a uniform fiber dosage may differ. This is a point that future research should address with larger sample sizes and extended follow-up.
Where this could go next
A practical next step would involve comparing various types of fiber, different doses, and durations among older adults.
Further investigation might also explore whether initial cognitive improvements persist after six or twelve months and whether they lead to fewer memory lapses in daily life.
Mechanistic studies could help clarify which metabolites increase with supplementation and how they influence brain networks. The remote design used in this study demonstrates that such research can be both feasible and inclusive.
The favorable safety profile and accessibility of these fibers lower barriers for thorough testing within community environments.
The pressing question isn’t whether the gut communicates with the brain, but rather how to optimize that dialogue for lasting cognitive benefits.
This study appears in Nature Communications.
