Fiber
FOS (Fructooligosaccharides)
Also known as: Fructooligosaccharides, Oligofructose
Short-chain prebiotic fiber that rapidly feeds bifidobacteria. More gas-producing than longer-chain fibers.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every FOS (Fructooligosaccharides) product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | NOW Foods Prebiotic Inulin Fiber | 81 A- | $0.31 |
| 2 | Swanson Epic Pro 25-Strain Probiotic | 76 B+ | $0.98 |
| 3 | Bluebonnet Nutrition MILK FREE PROBIOTIC ACIDOPHILUS & FOS POWDER | 69 B | $0.39 |
| 4 | Bluebonnet Nutrition MILK-FREE PROBIOTIC ACIDOPHILUS & FOS | 66 B- | $0.39 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much FOS (Fructooligosaccharides) should I take?
The typical range is 2-8 g daily. Start very low
When should I take FOS (Fructooligosaccharides)?
Any time. Optional.
Which form of FOS (Fructooligosaccharides) is best?
Powder — Sweet taste. Other forms in the catalog: Capsules.
Is FOS (Fructooligosaccharides) safe?
Commonly reported: Gas, Bloating, Cramping. Serious warnings: FODMAP issues. Safe
Which FOS (Fructooligosaccharides) supplement scores highest?
NOW Foods Prebiotic Inulin Fiber, at 81/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
Primary uses
- Prebiotic
- Bifidobacteria support
- Calcium absorption
How it works
- Rapidly fermented by bifidobacteria
- Increases SCFA production
- Enhances calcium absorption
Dosage
- Typical range
- 2-8 g daily
- Timing
- Any time
- With food
- Optional
- Duration
- Start very low
- Special populations
- FODMAP-sensitive avoid
Forms
- Powder
- Capsules
Safety
Common side effects
- Gas
- Bloating
- Cramping
Contraindications
- SIBO
- FODMAP intolerance
Products containing FOS (Fructooligosaccharides)
Top-scoring supplements in our catalog that list FOS (Fructooligosaccharides) on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Evidence notes
Effective prebiotic, may cause gas
Grade B: Some human trials support key claims; further confirmation needed.
Related in Fiber
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.