Quick answer

There is no official daily amount of inulin. Trials used 3 to 20 g a day of chicory inulin-type fructans: 5 to 8 g a day raised bifidobacteria, 8 to 10 g a day raised calcium absorption, and one bowel trial used 12 g. Gas grows with the amount, so the studied range is also the cautious one.^1,2,3,4

Key facts

An expert panel says most prebiotics need about 3 g a day or more to have an effect.⁵
Bifidobacteria rose at 5 g a day in two trials, and in one of them more people responded at 8 g.^2,6
The calcium trials used 8 to 10 g a day of chicory inulin mixed with oligofructose, for 6 weeks to a year.^3,7,8
The bowel trial gave 12 g a day, as 4 g three times a day, for 4 weeks.⁴
In a study of short-chain fructans, excess gas appeared above about 30 g a day, well above the amounts in most trials.⁹

What the trials used

No expert body has set a recommended amount of inulin, so the best guide is what the studies gave people. The amount depends on what the researchers were measuring, and the table lists the main ones side by side.^1,10

Daily amounts of inulin-type fructans in trials, by what was measured^{2,3,4,7,8,11,12,13,14}
What was measured	Amount a day	Length	Result
Bifidobacteria in stool	5 g and 8 g of inulin	2 weeks	Both amounts raised them
Bifidobacteria in stool	7.7 g, then 15.4 g, in snack bars	7 days, then 14 days	Raised
Calcium absorption in adolescents	8 g of inulin mixed with oligofructose	1 year	More absorbed
Calcium absorption after menopause	10 g of oligofructose-enriched inulin	6 weeks	More absorbed
Bowel movements	12 g of chicory inulin, as 4 g three times a day	4 weeks	Median 3 to 4 a week
Bowel movements	5, then 10, then 15 g of oligofructose	4 weeks per step	Raised only at 15 g
Stool weight and transit time	20 g of chicory inulin in ice cream	3 weeks	No change
Iron absorption	About 20 g of inulin in three portions	4 weeks	No change

Read the last two rows as limits, not failures. A fiber that feeds gut bacteria did not change stool weight or iron absorption at 20 g, so more is not a way to get a different result.^13,14

The amounts, one result at a time

An expert panel says most prebiotics need an oral dose of about 3 g a day or more to have an effect.⁵

In a trial of 30 healthy adults, 5 g and 8 g of inulin a day for 2 weeks both raised bifidobacteria, and more people responded at 8 g.²

Most calcium trials used 8 to 10 g a day of chicory inulin mixed with oligofructose. Across the studies FDA reviewed, amounts ranged from 3 to 40 g a day.³

The bowel trial of chicory inulin used 12 g a day, taken as 4 g three times a day, for 4 weeks.⁴

More did not reliably mean a bigger effect. In a 200 person trial, amounts from 2.5 to 10 g a day of short-chain fructooligosaccharides gave similar rises in bifidobacteria, and a low starting count predicted the larger rise.¹⁵

Reading the amount on a label

The Daily Value for dietary fiber on US labels is 28 g a day, and inulin may be counted in a label's dietary fiber.^16,17

Labels may give inulin in milligrams or grams, so convert before you compare: a thousand milligrams make one gram. Check the grams in one serving, and check whether the serving is one scoop, one capsule or several.

We found no source for the weight of a teaspoon of inulin powder, and powders differ in how tightly they pack. Use the grams on the label and the scoop that comes with the product, or a kitchen scale, rather than a teaspoon.

What's in ours

The label amount is 200 mg, which is 0.2 g, about one fifteenth of the 3 g an expert panel gives as the usual minimum for a prebiotic effect. That is why we make no inulin claim for this product.⁵

How much is too much, and who should ask first

We found no official upper limit for inulin. Trials in healthy adults used up to about 20 g a day for 2 to 4 weeks, and gas and other complaints rose with the amount.^13,14,18

In a study of short-chain fructans, excess gas appeared above about 30 g a day, rumbling and bloating above 40 g, and cramps and diarrhea around 50 g.⁹

Most healthy adults in trials had only mild complaints at 5 to 10 g a day, so there is no reason to start at the top of the range. If gas is a problem at your current amount, a smaller one is the first thing to try.^18,19

Children are a separate question. Food gives young children about 1.3 g a day on average, trials included people from 0 to 83 years old, and we found no official amount for a child, so ask a pediatrician before giving a supplement to a 2 or 3 year old.^1,20

People with irritable bowel syndrome or another long-term bowel condition, people who take levothyroxine and people who are pregnant or nursing should ask a doctor before choosing any amount.^21,22,23

Questions people ask

How many teaspoons of inulin is 5 g?

We found no source for that conversion, and it varies with the powder. Weigh it, or use the scoop and the grams per serving printed on your label.

Is 5 g of inulin enough?

For gut bacteria, two trials found bifidobacteria rose at 5 g a day. For calcium absorption the trials used 8 to 10 g a day, so 5 g is below what those studies tested.^2,3,6

Can I take inulin every day?

The longest trial gave 8 g a day for a year and absorption was still higher than with placebo at the end. There is no official upper limit, so ask your doctor about long-term use.^3,7

What is a safe amount of inulin for a toddler?

We found no official amount for children. Food supplies about 1.3 g a day to young children on average, and a pediatrician should decide on anything more.²⁰

See what we make

Every product shows its whole label and what its lab report covers. The store opens soon.

See the Full Measure line

Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.