Soluble corn fiber and polydextrose effects on stool weight in people
What it found
Eating 20 g a day of soluble corn fiber or polydextrose increased stool weight and frequency in healthy men and women.
Both fibers were well tolerated, though they caused more gas than a low-fiber control.
What they found
Studies in people
Stool weight and frequency
Both fibers led to heavier stools over 5 days compared with the low-fiber control. People also passed more stools per day during both fiber treatments. Daily stool output rose to 166 g with polydextrose and 157 g with soluble corn fiber, up from 125 g on the control.
Softer stools with polydextrose
Polydextrose made stools softer than both the soluble corn fiber and the low-fiber control. Soluble corn fiber did not change stool softness compared with the control.
Gut transit time unchanged
The time it took food to travel through the whole gut was about the same across all three treatments. Researchers measured this by having participants swallow tiny markers and tracking them in x-rays.
Gas and stomach noises
People reported more flatulence and stomach rumbling when eating either fiber compared with the low-fiber control. However, the average gas score was only 3 out of 10, which the authors describe as mild.
Stool acidity changes
Polydextrose lowered stool pH, making it more acidic, compared with the low-fiber control. Soluble corn fiber showed a similar trend but the difference was smaller.
What the authors conclude
- They conclude that both fibers produce a mild laxative effect when eaten at 20 g a day in muffins and cereal.
- The authors say these fibers can be added to regular diets to increase stool weight without causing serious stomach problems.
- They note that measuring short-chain fatty acids in stool needs standardized methods before results can be reliably compared across studies.
How it was done
Most people eat far less fiber than recommended amounts of 25 g a day for women and 38 g a day for men. The authors wanted to see if adding these two fibers to everyday foods could improve bowel habits without causing stomach problems.
Thirty-six healthy adults ate muffins and cereal containing either 20 g a day of polydextrose, 20 g a day of soluble corn fiber, or a low-fiber control. Each treatment lasted 10 days with a 2-week break between them. Participants collected their stools for the last 5 days of each period and filled out daily symptom questionnaires.
What it can’t tell you
- This trial lasted only 10 days per treatment, so it cannot show what happens when people eat these fibers for months or years.
- The study tested a specific dose of 20 g a day, so the effects of smaller or larger amounts are not known from this work.
Who paid
- Authors work at
- University of Minnesota, USA
The paper
- Title
- Polydextrose and soluble corn fiber increase five-day fecal wet weight in healthy men and women
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Timm DA, Thomas W, Boileau TW, Williamson-Hughes PS, Slavin JL (2013). Polydextrose and soluble corn fiber increase five-day fecal wet weight in healthy men and women. The Journal of nutrition. doi:10.3945/jn.112.170118Free full textPubMed 23427334DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error