Isomalt, gut bacteria and colon markers in nineteen healthy volunteers
What it found
Eating 30 g of isomalt daily for four weeks raised levels of bifidobacteria in the gut compared with eating regular sugar.
Lab tests showed gut bacteria broke down isomalt completely and produced high amounts of butyrate.
What they found
Studies in people
More bifidobacteria in people
After four weeks on isomalt, the number of bifidobacteria in stool rose by 47 percent and their share of total gut bacteria grew by 65 percent compared with the sugar period. Total bacterial counts stayed about the same.
Lower enzyme activity
The activity of a bacterial enzyme called beta-glucosidase dropped by 40 percent during the isomalt phase. Four other bacterial enzymes measured in stool did not change.
Stool chemicals unchanged
Levels of short-chain fatty acids, lactate, bile acids, ammonia, phenol and p-cresol in stool were similar whether people ate isomalt or sugar. Stool pH was also about the same in both periods.
Animal and lab studies
Lab fermentation results
In lab dishes, mixed human gut bacteria broke down isomalt completely within 14 hours. This produced high amounts of butyrate, more than what was seen with resistant starches in the same setup.
Bifidobacteria used isomalt
Several strains of human bifidobacteria grown in lab tubes used isomalt as their only food source. Some strains consumed almost all of it and grew just as well as they did on glucose.
What the authors conclude
- They conclude that isomalt boosts bifidobacteria in healthy people and should be considered a prebiotic carbohydrate.
- They suggest it might help support a favourable environment in the lining of the colon.
How it was done
Most isomalt passes through the small intestine undigested and reaches the colon, where gut bacteria ferment it. The authors wanted to find out if this widely used sweetener acts as a prebiotic by boosting helpful gut bacteria like bifidobacteria.
Nineteen healthy adults followed a controlled diet for two four-week periods, separated by a four-week break. In one period they ate foods sweetened with 30 g of isomalt daily, and in the other with 30 g of regular sugar. Researchers collected stool samples at the end of each period and also tested how gut bacteria handled isomalt in lab dishes.
What it can’t tell you
- This trial lasted only four weeks per diet, so it cannot show what happens when people eat isomalt over many months or years.
- Lab dish tests show how bacteria handle isomalt outside the body, which may differ from what happens inside a living digestive system.
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
- Full text
- 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/bjn20051589Free full textPubMed 16441915DOI
Summary written 1 Oct 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error