Isomaltooligosaccharide (IMO)

Last reviewed October 19, 2026

In plain words: Isomaltooligosaccharide (IMO) is a syrup sometimes sold as "fiber" in bars and snacks.

What the evidence review says

Isomaltooligosaccharide (IMO) is a syrup sometimes sold as 'fiber' in bars and snacks. The FDA has twice declined to count it as dietary fiber because the evidence did not show a fiber-like benefit. A study found it raised blood sugar much like ordinary sugar, so the concern is labeling, not a toxic effect.

The concern is mislabeling and a sugar-like glycemic effect, not a demonstrated toxic effect. FDA denied two citizen petitions to list IMO as dietary fiber (June 13, 2018, and January 9, 2020) because the evidence did not show a beneficial physiological effect. A randomized crossover found no meaningful difference in glycemic response versus a dextrose comparison and concluded that the tested IMO was digestible. In vitro work shows the usual fungal fiber assay underestimates digestion because mammalian sucrase-isomaltase does hydrolyze these links, slowly. Products that count IMO as fiber can overstate fiber and understate available carbohydrate.

• Source: Gourineni V et al., Nutrients, 2018 · doi:10.3390/nu10030301
• Source: Song YB et al., Food Chem, 2022 · doi:10.1016/j.foodchem.2022.132456

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This page is for general education. It is not medical advice and does not replace advice from your doctor, pediatrician, allergist or registered dietitian. Research changes; we review these pages when new evidence or rules come out. Last reviewed October 19, 2026.