Brain & Neurons

Probiotic and Fiber Drink Deters Dementia in New Japanese Study 

Middle-aged and older adults showed improvements in cognitive ability after drinking a mixture of probiotics — beneficial bacteria — and fiber.

By Daniel R. Miranda, Ph.D.

Key Points: 

  • A dairy drink containing the probiotic Bifidobacterium animalis and inulin — a fiber found in vegetables like artichokes and asparagus — doubled the cognitive performance scores of middle-aged and older adults. 
  • The probiotic and fiber combo also increased the levels of beneficial gut bacteria called Bifidobacteria. 

Millions of people across the globe suffer from dementia, with worldwide economic costs reaching $1.3 trillion in 2019, not to mention the unmeasurable physical, emotional, and psychological costs. Since dementia is preceded by mild cognitive impairment (MCI) — decrements in memory and thinking — countering MCI could deter the path to dementia.

Now, as reported in Nutrients, Azuma and colleagues from the Nihonbashi Cardiology Clinic in Tokyo may have found a way to protect against dementia. They showed that the cognitive abilities of 50- to 80-year-old participants improved after 12 weeks of drinking a probiotic and fiber concoction. Additionally, the levels of beneficial gut bacteria called Bifidobacteria were increased in the feces of the participants, suggesting successful colonization of the intestines. 

“This is the first randomized controlled trial to demonstrate the efficacy of [the probiotic] GCL2505 and [the fiber] inulin in improving memory function in the elderly,” the authors said.  

Beneficial Bacteria Deter Dementia

A total of 67 participants were divided into two groups. One group received a drink containing a probiotic called Bifidobacterium animalis and a fiber called inulin, while the other group received a placebo drink. After 12 weeks, the group that received the probiotic and fiber drink saw significant improvements in cognition compared to the placebo group. 

Improvements in overall cognitive performance were determined by the neurocognitive index, a score based on computerized tests that assess brain functions, such as memory, reaction time, and attention. These improvements in the neurocognitive index suggest that probiotics and fiber can counter cognitive decline. Although proteins, scans, and other markers of dementia were not tested, it is worth pondering whether these effects could potentially deter the path to dementia. 

(Azuma et al., 2023 | Nutrients) Probiotic and Fiber Improves Cognitive Performance. After 12 weeks, the change in neurocognitive index (Δ Neurocognitive index) from the group who drank probiotics and fiber (Active) was double that of the placebo group (Placebo), suggesting overall improvements in cognition.

Probiotics are living microorganisms, usually bacteria that when consumed can take residence in our intestine and begin to multiply, especially with the help of fiber, which bacteria eat. Azuma and colleagues found that the participants who drank probiotics and fiber had more beneficial Bifidobacteria in their feces. These findings suggest that the beneficial bacteria consumed by the participants had made it to the intestines and began to multiply by feeding off the fiber consumed by the participants. 

(Azuma et al., 2023 | Nutrients) Probiotic and Fiber Improves Good Gut Bacteria Levels. Compared to the placebo group (white), the probiotic and fiber-drinking group (black) had increased beneficial bacteria in their feces (Fecal Bifidobacteria) after 12 weeks, suggesting the bacteria had colonized their gut.

Improving Cognition by Maintaining Gut Health 

The findings of Azuma and colleagues demonstrate that consuming beneficial bacteria and fiber can improve cognitive performance, including memory, reaction time, and attention. By doing so, MCI could be reversed and the progression to dementia could be slowed or stopped. However, longer-term studies beyond the course of 3-months are needed to confirm this. 

“Because there is currently no effective pharmacological therapy to prevent the onset and progression of cognitive decline in the pre-dementia stage, the findings of this study suggest that continuous intake of GCL2505 and inulin may be an effective approach to protect memory function in the elderly,” conclude the authors.

Outside of Japan, it may be difficult to find the GCL2505 probiotic strain. But Bifidobacterium animalis (B. animalis), also known as B. animalis subspecies lactis, B. animalis subspecies animalis, or B. lactis can be found in various probiotic products, as well as foods like Kefir — a fermented milk drink and some yogurts. 

Is Fiber the Key?

While fiber may enhance the effects of probiotics by promoting their growth in the gut, it could also increase existing beneficial bacteria in the gut. Further studies are needed to untangle the effects of fiber and probiotics on cognition, but dietary fiber alone can reduce the risk of dementia. Moreover, while inulin and other fiber supplements are available, they may not be necessary for consuming the recommended 30 grams of fiber per day for older individuals. A diet rich in high-fiber foods like fruits, vegetables, lentils, and beans may do the trick. 

Participants & Dosage

Participants: 50- to 80-year-old individuals

Dosage: A drink containing 1 × 1010 colony-forming units of Bifidobacterium animalis subsp. lactis GCL2505 and 2.0 g of inulin per 100 g


Azuma, N., Mawatari, T., Saito, Y., Tsukamoto, M., Sampei, M., & Iwama, Y. (2023). Effect of Continuous Ingestion of Bifidobacteria and Dietary Fiber on Improvement in Cognitive Function: A Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients, 15(19), 4175.

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