THE BRAIN BEGINS IN THE GUT: How Prebiotics Help Preserve Memory

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What benefits your gut may also benefit your brain. A new study published in Nature Communications suggests that some of the simplest dietary supplements may help improve your memory.

FOOD FOR THE MICROBIOME, BENEFITS FOR MEMORY

A new twin study has found that taking protein and prebiotic supplements daily may improve memory performance in people over the age of 60. The findings attracted particular attention because the same visual memory and learning test used in the study is also employed to detect the early signs of Alzheimer’s disease. As part of the double-blind trial, researchers examined two inexpensive and widely available prebiotics derived from plant fibers that are sold over the counter in many countries. Prebiotics are non-digestible dietary compounds that stimulate the growth and activity of beneficial gut bacteria. One of the supplements was inulin, a member of the fructan family. The other consisted of fructooligosaccharides (FOS), which are commonly used as natural low-calorie sweeteners.

A TWIN STUDY: WHAT THE RESULTS REVEALED

Like the rest of the body, the brain gradually wears down and ages over time. Yet this process may be easier to counteract than previously thought. Researchers at King’s College London recruited 36 pairs of twins aged 60 and older. Within each pair, one twin received a daily prebiotic supplement together with a protein powder, while the other was given a placebo. After three months, the twins who had unknowingly been taking either inulin or FOS consistently performed better on cognitive tests. In addition, regular fiber supplementation was associated with small but measurable changes in the composition of the gut microbiome.

In particular, participants receiving the supplements showed an increase in the abundance of Bifidobacterium. Animal studies have also suggested that bifidobacteria may help reduce cognitive impairment by influencing communication along the gut–brain axis. As geriatric medicine researcher Mary Ni Lochlainn noted, “These changes in just 12 weeks are promising and offer hope for enhancing brain health and memory in our aging population”. According to her, further research into the gut–brain axis could pave the way for new strategies to extend a healthy, active life.

WHY TWIN STUDIES ARE SO IMPORTANT

King’s College London maintains the UK’s largest registry of adult twins. Research involving these twin pairs is particularly valuable because it makes it possible to distinguish more accurately between the effects of genetic factors and environmental influences on human health. Every individual has a unique microbiome — the community of microorganisms that inhabit the gut. Previous studies in rodents have shown that a high-fiber diet, including inulin and FOS, promotes the growth of beneficial bacteria in the large intestine. Research also suggests that some of these bacteria are associated with improved cognitive function in both animals and humans. Moreover, each year brings growing evidence of the close relationship between the gut and the brain. Some scientists even refer to the gut as the “second brain”. Nevertheless, the mechanisms underlying this interaction remain far from fully understood.

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LIMITATIONS AND NEW QUESTIONS

The findings suggest that certain microbiome-targeting foods could become part of future strategies for treating cognitive impairment. They complement a growing body of research indicating that specific nutrients may help slow cognitive decline. Geriatrician Claire Steves emphasizes that plant fibers such as those used in the study are affordable, safe, and potentially beneficial for a wide range of people. However, she notes that the next step is to determine whether these effects persist with longer-term use and in larger study populations.

THE GENDER QUESTION

It is important to note that the study did not reveal any significant physical changes among the participants. In particular, the supplements did not reduce age-related muscle loss, even though inulin and FOS are considered important for supporting musculoskeletal health. Moreover, the study population consisted predominantly of women. Although the researchers accounted for sex differences in their analysis, they acknowledge that the composition of the sample may have influenced the findings. Nevertheless, women are disproportionately affected by Alzheimer’s disease, and studies like this reinforce the idea that cognitive decline may be driven not only by processes within the brain itself but also by factors originating elsewhere in the body.

THE GUT, THE BRAIN, AND THE FUTURE OF THERAPY

According to the Lancet Commission on dementia, approximately 7% of the risk of developing Alzheimer’s disease is associated with elevated levels of low-density lipoproteins (LDL) in midlife — the particles responsible for transporting cholesterol and fatty acids throughout the body. A 2025 study conducted at King’s College London suggests that this factor may help explain why the disease is more common among women. Other research has shown that an imbalance in the gut microbiota — such as a reduced ratio of Bifidobacterium to Akkermansia — is associated with multiple sclerosis and with more severe disease progression. The gut plays a vital role in numerous physiological processes, including the functioning of the immune system and the central nervous system. Supporting the microbiome through prebiotics and probiotics may, in the future, open new avenues for treating a wide range of diseases.

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