fructooligosaccharides
FOS is inulin's little sibling — shorter chains, faster fermentation, same prebiotic job with a more clinical name.
Also appears on labels as: fructooligosaccharide · fructo-oligosaccharides · fos
What it is
Short-chain fructans (the label may say FOS), produced from sucrose or by trimming inulin. Shorter chains ferment faster and further up the gut than inulin's — a technical difference formulators occasionally exploit, and a distinction without much difference at label doses.
Why it's in pet food
Prebiotic positioning in 'digestive health' and senior formulas, often paired with a probiotic organism so the bag can say 'pre- and probiotics.' The pairing is coherent — one is bacteria, the other is their food.
How Bowlmark scores it
Scores are deterministic math over the printed label — the rules below apply to every product identically, and nothing estimates or fills in a blank.
Neutral: no bonus (the roster seats chicory root, not extracted fructans — same treatment as bare inulin), no deduction, no flag. Despite the '-saccharide' name and sucrose parentage, FOS is not on the sugars deduction list — it behaves as fiber, not sugar, and the roster sits with the physiology.
Foods that list fructooligosaccharides
Ranked by score where scores exist. Placement here is never sold.
- Hill's Science Diet Adult Large Breed Chicken & Barley Recipe91
- Hill's Science Diet Adult Large Breed Lamb Meal & Brown Rice Recipe91
- Hill's Science Diet Adult Light Small Bites Chicken Meal & Barley Recipe91
- Hill's Science Diet Adult 6+ Large Breed Chicken Meal, Barley & Rice Recipe90
- Hill's Science Diet Adult 7+ Chicken Meal, Barley & Rice Recipe90
- Hill's Science Diet Adult Chicken & Barley Recipe90
- Hill's Science Diet Adult Light Dry90
- Hill's Science Diet Adult Small & Mini Chicken & Brown Rice Recipe90
Compare foods that list fructooligosaccharides
Same species, same form, both scored — closest scores first, so the comparison is a real one.
- Hill's Science Diet Adult 6+ Large Breed Chicken Meal, Barley & Rice Recipe vs Hill's Science Diet Adult 7+ Chicken Meal, Barley & Rice Recipe
- Hill's Science Diet Adult 6+ Large Breed Chicken Meal, Barley & Rice Recipe vs Hill's Science Diet Adult Chicken & Barley Recipe
- Hill's Science Diet Adult 6+ Large Breed Chicken Meal, Barley & Rice Recipe vs Hill's Science Diet Adult Small & Mini Chicken & Brown Rice Recipe
- Hill's Science Diet Adult 7+ Chicken Meal, Barley & Rice Recipe vs Hill's Science Diet Adult Chicken & Barley Recipe
Sources
Related ingredients
Further reading
Cite this page
Bowlmark. "Fructooligosaccharides in pet food — what it is and how it scores." https://www.bowlmark.com/ingredient/fructooligosaccharides
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- Last verified August 12, 2026
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