Soluble corn fiber, reaction times and gut bacteria in adults
What it found
Taking 18 g of soluble corn fiber daily for 4 weeks sped up reaction times and increased a type of gut bacteria called Parabacteroides in adults aged 45 to 75.
The effect on reaction times depended partly on how much that bacteria changed.
What they found
Studies in people
Faster reaction times
People who took the corn fiber reacted faster on computer tasks that tested their ability to ignore distractions. Reaction times were quicker by about 10 to 14 milliseconds compared to the placebo. Accuracy stayed the same.
Gut bacteria changes
Corn fiber increased a group of gut bacteria called Parabacteroides by about fourfold in 90% of participants. Two other types of bacteria also rose. Overall variety of bacteria dropped slightly.
Digestive comfort
Stomach symptoms were mostly absent or mild during both periods. Gas scores rose slightly after taking corn fiber but stayed in the mild range. Bloating scores barely changed.
Memory and mood unchanged
The fiber did not change scores for relational memory, working memory, mood or stress compared to the placebo.
Animal and lab studies
Bacteria grown in lab
In lab tests, a specific species called Parabacteroides distasonis was able to grow using corn fiber as its food source. It showed a two-phase growth pattern over 14 hours.
What the authors conclude
- They conclude that 4 weeks of daily soluble corn fiber improved attention and shifted gut bacteria toward more Parabacteroides in middle-aged and older adults.
- Their exploratory analyses suggest the cognitive benefits may depend partly on how much Parabacteroides changed, though not in a simple way.
- They call for more research using detailed measurements of metabolites and different doses to better understand how this fiber affects the brain.
How it was done
Dietary fiber may support brain function through changes in gut bacteria, but human trials testing this idea are limited. About 95% of Americans do not eat enough fiber.
Forty-two healthy adults aged 45 to 75 took part in a crossover trial. Each person consumed 18 g of soluble corn fiber or a placebo daily for 4 weeks, with a break between periods. Researchers measured attention, memory, mood, gut bacteria and digestive comfort.
What it can’t tell you
- The study group was mostly white, female and highly educated, so the results might not apply to everyone.
- Because the trial lasted only 4 weeks, it cannot show whether these effects last longer.
- The researchers did not take blood samples, so they could not measure how much of the bacterial products actually reached the rest of the body.
Who paid
- Conflicts
- Conflict of interest HDH is an Editorial Board Member for The Journal of Nutrition and played no role in the Journal’s evaluation of the manuscript. All other authors report no conflicts of interest.
- Authors work at
- University of Illinois Urbana-Champaign, United States; Beckman Institute of Advanced Science and Technology, United States
The paper
- Title
- Effects of Soluble Corn Fiber Consumption on Executive Functions and Gut Microbiota in Middle to Older Age Adults: A Randomized Controlled Crossover Trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Alvarado DA, Holthaus TA, Martell S, et al (2026). Effects of Soluble Corn Fiber Consumption on Executive Functions and Gut Microbiota in Middle to Older Age Adults: A Randomized Controlled Crossover Trial. The Journal of nutrition. doi:10.1016/j.tjnut.2026.101473Free full textPubMed 41825740DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error