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Dietary fiber · in-depth review

Fructooligosaccharides (FOS)

Fructooligosaccharides (FOS)

Fructooligosaccharides are short-chain β(2,1) fructo-oligosaccharides. The small intestine barely absorbs them; bifidobacteria ferment them rapidly only in the colon, used for microbiota and stool form.

Also known asFOSfructooligosaccharidesoligofructosescFOS
Related symptomsConstipationBloating

Marked asPrimarySupporting

Primary

Increase intestinal bifidobacteria

Fructose units in FOS are linked by β(2,1) bonds that gastric enzymes cannot cut. After they enter the proximal colon, bifidobacteria rapidly ferment them into short-chain fatty acids. Trials in healthy adults can show fecal bifidobacteria rising with continued use.

Primary

Improve stool form and bowel movements

After a refined diet the microbiota is often monotonous; after one to two continuous weeks, changes in bowel frequency and stool firmness are more often seen. Bloating and gas are most obvious when fermentation comes too fast; the gut needs time to adapt to this proximal fermentation.

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Constipation

After a refined diet the microbiota is often monotonous; after one to two continuous weeks, changes in bowel frequency and stool firmness are more often seen. People with hard stools and longer intervals more often notice frequency and softness after several continuous weeks.

Bloating

After a refined diet the microbiota is often monotonous; after one to two continuous weeks, changes in bowel frequency and stool firmness are more often seen. People whose belly swells after meals and who loosen a belt notch more often notice abdominal softness and less gas after several continuous weeks.

Functional constipation

Fructose units in FOS are linked by β(2,1) bonds that gastric enzymes cannot cut. People with functional constipation who strain to pass stool more often notice softness and less straining after several continuous weeks.

Irritable bowel syndrome

After a refined diet the microbiota is often monotonous; after one to two continuous weeks, changes in bowel frequency and stool firmness are more often seen. People who cycle between pain, bloating, and irregular stools more often notice a calmer abdomen and more regular bowel habits after several continuous weeks.

With foodTake with plenty of water; start low. Fine with meals.
Best timeMorning or with main meals; avoid one large evening dose.
SolubilityWater-soluble

After continued use, reassess by how you feel and whether you still need it.

General wellnessTypical daily intake: FOS 5–10 g, starting at 2.5 g and increasing gradually.
Specific needsCommon adult upper limit about 15–20 g/day; reduce if you have IBS or marked gas, and do not exceed this on your own long term.

How oftenUsually fine to use daily; adjust to personal need.

Cautions

If you take medicines, are pregnant, or have a chronic condition, ask a clinician before use.

Interactions

  1. Separate from oral medicines
Common side effects

· Some people may notice mild digestive or other discomfort.

Rare but important

· If discomfort persists or you worry about drug interactions, seek professional advice.

Long-term dependenceNo typical addiction evidence; do not exceed labeled amounts on your own long term.

Sources

These are institution pages you can check—not a certification of this ingredient.

Medical disclaimerThis page is compiled by the HerbBB editorial team for general health information only. It is not a substitute for advice from a doctor, pharmacist, or other qualified clinician. If you have a health condition, take medicines, or are pregnant or breastfeeding, speak with a professional first.