Taking a Daily Fiber Supplement Can Boost Brain Function in Older Adults, Study Finds

A new study suggests that the daily intake of fiber supplements could enhance cognitive function in older adults.

The research, appearing in the scientific journal Nature Communications, revealed that participants over 60 years old who consumed prebiotic fiber supplements for a period of 12 weeks demonstrated a significant improvement in memory and cognitive tests compared to those who did not.

The scale of the study was relatively small, with only 72 individuals, consisting of 36 twin pairs, and it does not conclusively establish that fiber can enhance cognition, says Amy Reichelt, PhD, a nutrition and neuroscience investigator at the University of Adelaide in South Australia, who didn't contribute to the new research. However, it does establish a correlation.

Reichelt highlighted to Health that the research shows a relationship between the fiber supplement and improved cognition, rather than proving a clear cause-and-effect scenario.

While the findings are intriguing, claims Thomas R. Vidic, MD, a member of the American Academy of Neurology based in Elkhart, Indiana, he notes that the medical community must exercise caution when drawing broad conclusions from the study.

“The connection between the gut and brain is just beginning to be scrutinized; we are only in the early stages of this understanding,” Vidic told Health.

The goal of the researchers was to investigate if alterations to the gut microbiome driven by fiber supplements could bolster cognition and muscle function.

For this test, one twin from each pair was randomly selected to consume a daily prebiotic fiber supplement - inulin, a dietary fiber, or fructooligosaccharides (FOS), a plant-based carbohydrate for three months. Prebiotics are a form of fiber that the body can't break down but benefit the gut's probiotics (beneficial bacteria).

The other twin from each duo was given a placebo each day. All the mostly female participants were uninformed if they had obtained the prebiotic, and participating subjects also consumed a daily protein supplement and performed resistance exercise during the trial period.

At the conclusion of the 12 weeks, the participants' stool samples were tested by the investigators. The results showed an upsurge in beneficial gut bacteria such as Bifidobacterium, in individuals consuming prebiotics, a bacterium that other research has linked to cognitive enhancements.

However, when evaluating muscle strength, no substantial differences were observed between the two groups concerning how swiftly participants could rise from a seated position.

In cognitive testing, investigators found that the group consuming fiber supplements achieved higher scores on the visual memory and new learning components of the Paired Associates Learning test, which can indicate early Alzheimer’s disease. Compared to those consuming the placebo, the supplement users made half as many errors on this test.

Joel Salinas, MD, a clinical assistant professor of neurology at NYU Langone Health and chief medical officer at Isaac Health, mentioned to Health that assessing the significance of the results is challenging because the researchers amalgamated parts of the cognitive tests into a single score.

According to Salinas, the meaning of the results for a larger demographic is as yet uncertain due to limited data. The study does not clarify how fiber affects the risk of developing dementia or cognitive decline.

Researchers are starting to comprehend the interaction between gut health and the brain, with most of the research focusing on the psychological effects of microbiome changes, stated Salinas.

But, Reichelt explained, there is some understanding about how fiber and cognition might affect each other.

“Our ingested foods are fermented by gut microbes, and the byproducts of this fermentation can enter the bloodstream and reach the brain,” she said.

After this, the gut bacteria synthesize neurochemicals, Reichert added.

“Alterations in the gut microbiota composition due to fiber may impact the production and availability of these neurochemicals, subsequently affecting mood regulation, cognitive function, and behavior,” Reichert continued.

Hariom Yadav, PhD, director of the University of South Florida Center for Microbiome Research in Tampa, Florida, disclosed to Health that fiber might also reduce inflammation, a significant risk factor in cognitive decline.

Salinas added that older individuals considering a fiber supplement for boosting cognition should recall that the study linked prebiotics with an improved performance on just one cognitive test; it did not conclusively demonstrate that fiber enhances mental performance.

Even though there is no definitive proof that fiber improves cognition, evidence suggests it's beneficial for brain and overall health across all age groups.

“We can safely say that implementing more fiber-containing foods into one’s diet is beneficial,” Thomas M. Holland, MD, an instructor in digestive diseases and nutrition at Rush University in Chicago, told Health. 

Reichert emphasized that most people can get the fiber they need from a balanced diet—good sources include fruits, veggies, and whole grains. However, those who rely heavily on “junk food” may need to speak to a healthcare provider about taking a supplement.

“Supplements are generally only helpful when there’s a deficit in your diet,” Salinas said. “If you want to take a supplement to enhance your health, make sure it’s safe, affordable, and provides a benefit.”