The health of your gut might be surprisingly beneficial for your brain as it ages. Recent research highlights the link between gut health and cognitive function, revealing methods to enhance memory and overall brain health.
A groundbreaking study involving twins has discovered that daily supplementation of protein and prebiotics can enhance memory test results in individuals over 60. Published in 2024, these findings are particularly relevant, as the same memory assessment is employed to identify early signs of Alzheimer’s disease.
This double-blind trial examined two affordable plant-based prebiotics readily available in over-the-counter supplements worldwide. Prebiotics are non-digestible substances that promote the growth of beneficial gut microbes.
One supplement used in the study was inulin, a type of dietary fiber classified as a fructan. The other was fructooligosaccharide (FOS), a plant carbohydrate often utilized as a natural low-calorie sweetener.
Watch the video below for a summary of the research:
To investigate how these supplements influence aging brains, researchers from King’s College London recruited 36 pairs of twins, all aged 60 or older.
The pairs were randomly assigned: one twin received a daily prebiotic mixed into protein powder, while the other received a placebo powder.
Three months later, twins who unknowingly consumed inulin or FOS generally achieved higher scores in cognitive tests. Moreover, the daily intake of fiber supplements correlated with minor shifts in the gut microbiome between the twins.
The beneficial Bifidobacterium was notably more abundant among those taking inulin or FOS.
Research on mice indicates that Bifidobacterium can alleviate cognitive declines by enhancing gut-brain communication.
Mary Ni Lochlainn, a geriatric medicine researcher at King’s College London, expressed excitement about the study’s results, noting, “Seeing such changes in just 12 weeks is incredibly promising for enhancing brain health and memory in older adults.” She added, “Unlocking the mysteries of the gut-brain axis may offer innovative ways to promote healthier aging.”
King’s College houses the largest adult twin registry in the UK, and twin studies are extremely valuable for distinguishing between genetic and environmental influences on health.
Previous studies on rodents suggest that high-fiber supplements, including inulin and FOS, can nurture the colon’s microbiome, allowing beneficial bacteria to thrive.
These friendly bacteria also correlate with enhanced cognitive performance in both mice and humans.
Research is accumulating demonstrating the link between gut health and brain function, with increasing numbers of experts referring to the gut as the body’s ‘second brain.’
However, the precise mechanisms by which these two systems interact remain unclear.
This twin study at KCL suggests that consuming certain ‘brain foods’ could be an effective method for combating cognitive decline and adds to previous research indicating that specific nutrients may help slow brain aging.
Geriatrician Claire Steves from KCL pointed out that “These affordable plant fibers are easily accessible, which could assist many during these financially challenging times. They are also safe and well-tolerated.” She emphasized, “Our next step is to explore whether these benefits are maintained over extended periods and with larger groups.”
While prebiotics seem to enhance some cognitive abilities for the aging brain, particularly in memory and processing, significant improvements in physical health were not observed.
Muscle loss did not show signs of improvement among aging twins consuming high-fiber supplements, despite the importance of inulin and FOS in musculoskeletal health.
The twins involved in this trial were predominantly female, and although researchers adjusted for sex differences in their analysis, they acknowledge potential selection bias within the KCL twin cohort.
Nonetheless, data suggests women are at a higher risk for Alzheimer’s disease, supporting the emerging perspective that cognitive decline may not solely stem from brain health, but could also involve external influences.
A recent Lancet Commission for Dementia estimated that 7 percent of the risk for Alzheimer’s is associated with high midlife levels of low-density lipoprotein, which transports cholesterol and fatty acids throughout the body.
This risk factor might explain why women develop Alzheimer’s at twice the rate of men, as outlined in a 2025 study led by King’s College London.
Related: 117-Year-Old Woman’s Diet Could Help Us All Live Longer
Researchers also reported in 2025 that a decreased ratio of Bifidobacterium to Akkermansia among gut bacteria in humans and mice is associated with multiple sclerosis and correlates with more severe disease.
The gut plays an integral role in various bodily systems, including the immune and nervous systems. Providing its microbiome with certain prebiotics and probiotics has the potential to treat numerous diseases and conditions.
The study was published in Nature Communications.
An earlier version of this article was published in March 2024.
