Isomalt and gut bacteria in healthy volunteers
What it found
In people, eating isomalt daily for 4 weeks increased bifidobacteria in stool and lowered one bacterial enzyme, compared with sucrose.
In lab tests, isomalt was broken down by bifidobacteria and produced high butyrate levels.
What they found
Studies in people
Gut bacteria shift
Stool tests showed more bifidobacteria after the isomalt diet than after the sucrose diet.
Bacterial enzyme activity
During the isomalt phase, the activity of bacterial beta-glucosidase went down. Other enzymes tested (beta-glucuronidase, sulfatase, nitroreductase and urease) stayed the same.
Faecal polyamines
Most polyamines in stool were similar between the two periods. Cadaverine tended to be lower after isomalt.
Other stool markers
Short-chain fatty acids, lactate, bile acids, neutral sterols, nitrogen, ammonia, phenol and p-cresol in stool were not affected by eating isomalt.
Animal and lab studies
Lab fermentation
In lab tests, several bifidobacteria strains broke down isomalt and produced high levels of butyrate.
What the authors conclude
“Isomalt, which is used widely as a low-glycaemic and low-energy sweetener, has to be considered a prebiotic carbohydrate that might contribute to a healthy luminal environment of the colonic mucosa.”
Also in their conclusions
- They say isomalt should be considered a prebiotic carbohydrate.
- They suggest it might contribute to a healthy environment in the colon.
How it was done
Much of the isomalt eaten reaches the colon because it is poorly digested in the small intestine, but little was known about how it affects gut bacteria.
Nineteen healthy volunteers ate a controlled diet with either 30 g isomalt or 30 g sucrose daily for two 4-week periods, in a double-blind, placebo-controlled, cross-over design. Stool samples were collected at the end of each phase and tested for bacteria and other markers. Isomalt fermentation was also tested in the lab.
What it can’t tell you
- We summarised it from the abstract only.
- The study lasted only 4 weeks per phase, so it cannot show what happens over longer periods.
- The findings are from a small group of healthy volunteers and may not apply to other people.
Who paid
- Authors work at
- German Institute of Human Nutrition Potsdam-Rehbrücke, Germany
The paper
- Title
- Effect of isomalt consumption on faecal microflora and colonic metabolism in healthy volunteers
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Abstract only
- Cite
- Gostner A, Blaut M, Schäffer V, et al (2006). Effect of isomalt consumption on faecal microflora and colonic metabolism in healthy volunteers. The British journal of nutrition. doi:10.1079/bjn20051589PubMed 16441915DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error