The Power of Prebiotics: Enhancing Memory and Cognition in the Elderly

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What if protecting your brain from the ravages of aging was as simple as stirring a cheap, plant-based powder into your morning smoothie? A groundbreaking new study suggests this tantalizing possibility.

A randomized, double-blind trial in older adult twins found that taking prebiotic supplements containing inulin or FOS daily for 12 weeks led to improved scores on memory tests and beneficial changes in gut bacteria compared to a placebo. The findings point to the potential of these affordable, over-the-counter supplements to boost brain function in the elderly population.

In the quest to maintain mental sharpness throughout the lifespan, scientists are increasingly turning their attention to the complex relationship between the gut and the brain. A pioneering new study1 has found that supplementing the diet with specific plant fibers known as prebiotics can lead to improved memory and cognitive performance in adults over 60, possibly by altering the composition of the gut microbiome.

The randomized, double-blind trial, led by researchers at King's College London, involved 36 pairs of twins over the age of 60. Within each pair, one twin was assigned to take a daily prebiotic supplement mixed into a protein powder, while the other twin received a placebo powder. The prebiotics used in the study were inulin, a type of fructan fiber, and fructooligosaccharides (FOS), a plant-based carbohydrate, known to feed 'good' bacteria within the gut. Both are readily available and affordable over-the-counter supplements.

After just 12 weeks, the twins taking the prebiotic supplement generally achieved higher scores on tests of visual memory and learning compared to their placebo-assigned counterparts. Notably, the cognitive assessment used in the study is the same one used to detect early warning signs of Alzheimer's disease, suggesting the findings could have implications for staving off this devastating form of dementia.

To explore the potential mechanisms behind the brain benefits, the researchers analyzed stool samples from the participants. They discovered that the prebiotic supplements were associated with modest alterations in the gut microbiome, including an increase in beneficial Bifidobacterium bacteria. Prior studies in mice2 have shown that Bifidobacterium can reduce cognitive deficits by modulating the communication channels between the gut and the brain, known as the gut-brain axis.

Mary Ni Lochlainn, a geriatric medicine researcher involved in the study, expressed enthusiasm about the results, stating, "We are excited to see these changes in just 12 weeks. This holds huge promise for enhancing brain health and memory in our aging population. Unlocking the secrets of the gut-brain axis could offer new approaches for living more healthily for longer."3

The use of twins in the study design helps to disentangle the influence of genetics versus environmental factors like diet, as twins share a large proportion of their genetic makeup. Previous research in rodents4 had already hinted that prebiotic fibers like inulin and FOS can nourish the gut microbiome in beneficial ways, promoting the growth of "good" bacteria. Some of these microbial strains have been linked to better cognitive function in both animal models and humans.

However, the precise mechanisms by which the trillions of microbes in our gut communicate with our central nervous system remain largely mysterious. The emerging field of "psychobiotics"5 is attempting to elucidate this complex interplay and develop targeted interventions to improve mental health via the microbiome.

While the prebiotic supplements in the study showed promise for enhancing memory and information processing speed, they did not appear to impact muscle loss, which often goes hand-in-hand with cognitive decline in aging. This is despite previous evidence pointing to inulin and FOS as important factors for maintaining musculoskeletal health.

Geriatrician Claire Steves of KCL noted the practical advantages of the prebiotic fibers, saying, "These plant fibers, which are cheap and available over the counter, could benefit a wide group of people in these cash-strapped times. They are safe and acceptable too."3 However, the researchers caution that larger and longer-term studies will be necessary to confirm whether the positive effects are enduring.

As females are known to be at higher risk for Alzheimer's and other forms of dementia, it's notable that the majority of twins in the study were women. While the researchers controlled for sex differences in their analysis, they acknowledge the need for a more diverse sample in future trials to ensure broad applicability of the results.

The study adds to the growing recognition that age-related cognitive decline is a complex, multifaceted process that extends beyond the brain itself. By manipulating the gut microbiome, we may be able to tap into the far-reaching influence of our "second brain" to support healthy aging of the mind. With further research, prebiotic supplements could potentially emerge as an accessible, natural tool to help older adults hold onto their memories and mental faculties well into their golden years.

Learn more about the benefits of prebiotics here.

Learn more about natural approaches to prevent or mitigate neurodegenerative disorders here.


References

1. Ni Lochlainn MN, Spencer SEF, Cox SR, Brett FH, Walsh G, Malcomson FC, et al. Prebiotic supplement effects on cognitive function, muscular strength and gut microbiome in healthy older adults: a double-blind randomised placebo controlled trial. Nat Commun [Internet]. 2023 Jan 31 [cited 2024 Mar 4]; 14:560. Available from: https://www.nature.com/articles/s41467-023-36291-9

2. O'Hagan C, Li JV, Marchesi JR, Plummer S, Garaiova I, Good MA. Long-term multi-species Lactobacillus and Bifidobacterium dietary supplement enhances memory and changes regional brain metabolites in middle-aged rats. Neurobiol Learn Mem. 2017 Oct; 144:36-47. 

3. King's College London. Prebiotic supplements modulate cognition and the gut microbiome in older people [press release]. London; 2023 Jan 31 [cited 2024 Mar 4]. Available from: https://www.kcl.ac.uk/news/prebiotic-supplements-modulate-cognition-and-the-gut-microbiome-in-older-people

4. So D, Whelan K, Rossi M, Morrison M, Holtmann G, Kelly JT, et al. Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis. Am J Clin Nutr. 2018 Apr 25; 107(6):965-983. 

5. Sarkar A, Lehto SM, Harty S, Dinan TG, Cryan JF, Burnet PWJ. Psychobiotics and the Manipulation of Bacteria-Gut-Brain Signals. Trends Neurosci. 2016 Nov; 39(11):763-781.

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