Low-cost dietary supplements are boosting scientists' interest in the role of the gut in maintaining brain health, after a recent study showed that taking certain types of prebiotics daily may improve memory in older adults.
This led to the launch of a new clinical trial to investigate its ability to reduce cognitive decline and lower the risk of developing dementia.
A study published in the journal Nature Communications found that taking protein and prebiotic supplements daily improved the performance of people over 60 years old in memory tests, after an experiment conducted on 36 pairs of twins.
The study has garnered widespread attention in scientific circles, having been cited nearly one hundred times since its publication, and has paved the way for new clinical trials exploring the relationship between gut health and brain function.
Later, researchers from Wageningen University in the Netherlands launched a clinical trial called PRECODE, which aims to study the effect of prebiotic supplements on gut and brain health in older adults suspected of having cognitive decline.
This is the first human study to examine the combined effects of three types of dietary fiber on both the gut microbiome and cognitive functions: inulin from chicory, resistant dextrin, and a polysaccharide from seaweed, compared to a placebo, maltodextrin.
The trial involves people over the age of 60, who take these supplements twice a day for 26 weeks after mixing them with water, tea, or coffee, and undergo periodic brain scans and cognitive tests, with the final results to be announced in 2027.
Inulin is one of the supplements that has attracted the attention of researchers after its success in a previous study. It is a type of dietary fiber that feeds beneficial bacteria in the intestines.
In the first study, the researchers tested two types of plant-based prebiotics available without a prescription in many countries: inulin and fructooligosaccharide (FOS), a plant carbohydrate that is also used as a low-calorie natural sweetener.
The researchers randomly divided 36 pairs of twins, so that one twin took a prebiotic supplement mixed with protein powder, while the other received a placebo powder, without either of them knowing which supplement they were taking.
After three months, participants who consumed inulin or fructooligosaccharide scored better on cognitive ability tests compared to the other group.
The analysis also showed changes in the gut microbiome, represented by an increased abundance of beneficial Bifidobacterium bacteria in those who took these supplements, bacteria that animal studies indicate may help reduce cognitive decline by regulating communication between the gut and the brain.
Mary-Nee Loughlin, a researcher in aging medicine at King's College London, said that the emergence of these changes in just 12 weeks is a promising indicator of the potential to improve brain health and memory in older adults, adding that understanding the mechanisms of communication between the gut and the brain may open the door to new ways of promoting healthy aging.
These findings are based on growing scientific interest in the gut-brain axis, the communication network between the digestive and nervous systems. Accumulating research suggests that the gut microbiome plays not only to digestion but may also influence immunity and brain function; some researchers even refer to the gut as the "second brain," although the mechanisms of this influence are still being investigated.
Claire Steves, a gerontologist at King's College London, said that these plant fibers are inexpensive, readily available and safe to use, making them a promising option if long-term studies prove their effectiveness.
She added that the next step is to ensure that these benefits last for longer periods and to test them on larger numbers of participants, which is what the PRECODE trial is aiming for.
Researchers believe that the success of this experiment may pave the way for the use of simple nutritional supplements to support brain health and reduce cognitive decline in the elderly, but they emphasize that more studies are still needed before these supplements can be adopted as a therapeutic or preventative measure.
