Prebiotics & Cognitive Function

Results of a randomized controlled trial performed to evaluate the effectiveness of a prebiotic supplement on both muscle function and cognition in a healthy older population were recently published in Nature Communications. To limit genetic confounding, this study was conducted among twins (monozygotic and dizygotic) and is known as the PRebiotic and PrOtein on Muscle in Older Twins (PROMOTe) trial. Researchers from King’s College London randomized one twin from each pair (aged 63-83 years, an average of 73) to receive placebo and the other twin to receive 7.5 g of a prebiotic (comprised of inulin, 3.375 g, and fructooligosaccharides 3.488 g) per day for 12 weeks. Additionally, all participants in both groups received 3.32 g of a branched-chain amino acid powder daily (containing l-leucine, 1.66 g, l-isoleucine, 0.83 g, and l-valine, 0.83 g), and were advised to perform resistance exercises (squats, calf raises, sit-to-stand, etc.) at least twice per week.

No effect of prebiotic supplementation on muscle function was observed, including on the primary outcome or chair rise time, as well as secondary outcomes including hand grip strength, Short Physical Performance Battery (SPPB), or self-reported physical activity. However, microbiome analyses indicate that the prebiotic did impact the composition of the gut microbiota; many differences were found between groups, perhaps most notably an increase in Actinobacteria, especially Bifidobacterium, with prebiotic vs. placebo.

Additionally, the prebiotic appeared to improve cognition compared to placebo, assessed using CANTAB (Cambridge neuropsychological test automated battery) cognitive tests. Perhaps most important was a reduction in the number of errors in the Paired Associates Learning test, a memory test identified as a possible marker for diseases such as Alzheimer’s. Though a larger and more specific clinical trial should confirm and expand on these findings, previous studies suggest a prebiotic-associated improvement in cognition is possible.