This page shows what was measured, who it was measured in, and what that does not settle.
What Psyllium husk does in the body
The gel also slows how quickly sugar from a meal reaches the bloodstream.
Psyllium husk is a seed coat that absorbs many times its weight in water and turns into a thick gel. That gel does three physical things. In the small intestine it traps bile acids, which the body normally recycles, so they leave in the stool and the liver has to make more — and making bile acids consumes cholesterol, which is why LDL falls. And because psyllium is barely eaten by gut bacteria, the gel is still intact in the colon, where its trapped water softens hard stool and firms loose stool. No receptor, no enzyme, no absorption into the body at all.
Why people take it. Taken for constipation and regularity, and to lower cholesterol
What happened in people
LDL cholesterol fell 0.33 mmol/L and non-HDL 0.39 mmol/L across 28 randomised trials in 1,924 people
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
That psyllium reduces cardiovascular events, which no trial has tested — the claim rests on the LDL surrogate
Where it acts
Lumen of the small intestine, where the gel forms and binds bile acids, and the colon, where the retained water changes stool form. It is not absorbed.
Kind of result
A number that stands in for health
Supervision
Not usually supervised: sold as a supplement or food ingredient where recorded. That is a legal category, not a safety judgement.
What the registries record it as
The substance registry classes this as mixture.
FDA substance registry · 0SHO53407G · read 2026-08-29
The supplement label database classes it as botanical, under the name Psyllium (unspecified).
A person wrote this explanation into the record, with the studies named in the path below.
The recorded use, written for a reader without medical training. Not signed off.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 145 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
Randomisation
Randomisation means chance decides who gets which treatment.
A picture of it, and where the picture fails
It is like a coin toss deciding the groups.
Where that stops being true. A coin toss is fair once. Fairness here comes from doing it for everyone.
What people get wrong. It is thought to make groups identical. It makes them similar on average, including on things nobody measured.
Allocation of participants to arms by a chance process, so that unmeasured factors are balanced in expectation.
Absolute difference
An absolute difference is how many more people in a hundred were affected.
A picture of it, and where the picture fails
It is like counting heads in two rooms of a hundred.
Where that stops being true. Heads are easy to count. Study results carry a margin of error too.
What people get wrong. It is confused with a percentage change, which can look far larger.
The arithmetic difference in event rates between arms.
Confidence interval
A confidence interval is the range the true answer is likely to sit in.
A picture of it, and where the picture fails
It is like a weather forecast giving a range rather than one number.
Where that stops being true. A forecast range covers tomorrow. This one covers what the study could resolve.
What people get wrong. The middle number is read as the answer. A range crossing zero means no change is still possible.
An interval estimate that would contain the true parameter in a stated proportion of repeated studies.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Change in LDL cholesterol, non-HDL cholesterol and apolipoprotein B
✓ The study showed what it set out to show
Who was studied
Jovanovski 2018 meta-analysis of psyllium and blood lipids
How many people
1924
Study design
Systematic review and meta-analysis of 28 randomised controlled trials
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
LDL -0.33 mmol/L (95% CI -0.38 to -0.27), P < 0.00001; non-HDL -0.39 mmol/L (95% CI -0.50 to -0.27), P < 0.00001
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. All lipid endpoints are surrogates. No randomised trial has tested psyllium against cardiovascular events, and the authorised FDA claim rests on the same surrogate.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral powder, granules, wafer or capsule; not absorbed at any point
Interval reported. 95% CI -0
Written into the record, not signed off as a reviewed claim.
Change in total and LDL cholesterol on 10.2 g/day psyllium versus cellulose placebo
✓ The study showed what it set out to show
Who was studied
Anderson 2000 meta-analysis of psyllium adjunctive to a low-fat diet
How many people
656
Study design
Meta-analysis of 8 controlled trials
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Total cholesterol -4% (P < 0.0001); LDL -7% (P < 0.0001); apoB:apoA-I ratio -6% (P < 0.05); no effect on HDL or triglycerides
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. All subjects completed an 8-week low-fat diet lead-in first, so the effect measured is strictly additive to diet and is not a standalone result.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral powder, granules, wafer or capsule; not absorbed at any point
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Stool water content +2.33% versus +0.01% (P = 0.007); total output 359.9 versus 271.9 g/week (P = 0.005); bowel movements 3.5 versus 2.9 per week in week 2 (P = 0.02)
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Bowel movement frequency did not differ in treatment week one. Docusate is itself a weakly evidenced comparator, so this is a win against a low bar.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral powder, granules, wafer or capsule; not absorbed at any point
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Change in fasting blood glucose and HbA1c by baseline glycaemic status
✓ The study showed what it set out to show
Who was studied
Gibb 2015 meta-analyses of psyllium and glycaemic control
How many people
35
Study design
Eight meta-analyses across 35 randomised controlled studies
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
In type 2 diabetes: fasting glucose -37.0 mg/dL (P < 0.001); HbA1c -0.97 percentage points, -10.6 mmol/mol (P = 0.048)
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. No significant glucose lowering in euglycaemic subjects. The search included unpublished clinical records held by Procter & Gamble, the manufacturer of the leading psyllium brand. Sample size here counts studies, not participants.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral powder, granules, wafer or capsule; not absorbed at any point
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Relative risk of remaining symptomatic after fibre therapy
✓ The study showed what it set out to show
Who was studied
Moayyedi 2014 meta-analysis of fibre supplementation in irritable bowel syndrome
How many people
906
Study design
Systematic review and meta-analysis of 14 randomised controlled trials
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
All fibre RR 0.86 (95% CI 0.80 to 0.94), NNT 10; soluble fibre RR 0.83 (95% CI 0.73 to 0.94), NNT 7; bran RR 0.90 (95% CI 0.79 to 1.03), not significant
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Bran showed no benefit but also no evidence of harm. The soluble-fibre trials pooled several different fibres, so the estimate is not psyllium-specific.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral powder, granules, wafer or capsule; not absorbed at any point
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 5 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Psyllium husk
What a person takes: Oral powder, granules, wafer or capsule; not absorbed at any point.
The measurement behind this step
Sold in the United States both as a dietary supplement and as an OTC bulk-forming laxative, and uniquely among the entries in this file it carries an FDA-authorised health claim written into 21 CFR 101.81. That regulation requires labelling consistent with 21 CFR 101.17(f), the warning provision for these products, and requires all general health claim conditions of 21 CFR 101.14. Capsules deliver far less psyllium per unit than powder, so reaching the dose used in the lipid trials by capsule requires a large number of them. Product husk purity and particle size affect gel formation and are not standardised across brands.
Getting in
It absorbs water and becomes a gel, and that is the entire pharmacology
Psyllium husk holds many times its weight in water. There is no receptor and nothing enters the bloodstream — every effect it has comes from the physical properties of that gel.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
The active fraction is a highly branched arabinoxylan in the seed coat, which hydrates into a viscous gel. Viscosity, not solubility, is the property that predicts clinical effect: McRorie and McKeown group psyllium with beta-glucan and raw guar gum as high-viscosity gel formers, and separate them from non-viscous soluble fibres such as inulin and fructooligosaccharides that do not produce the same benefits.
The gel traps bile acids so the liver has to make more
Bile acids are normally reabsorbed and reused. Trapped in the gel, they leave the body instead, and the liver must build replacements out of cholesterol.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Sequestration of bile acids in the ileal lumen interrupts enterohepatic circulation, increasing faecal bile acid loss. The hepatocyte compensates by upregulating CYP7A1, the rate-limiting 7-alpha-hydroxylase of bile acid synthesis, which consumes hepatic cholesterol and drives compensatory upregulation of the LDL receptor. Serum LDL falls as a consequence — the same mechanistic route as a bile acid sequestrant drug, achieved physically.
The gel makes the contents of the small intestine thicker, so sugars diffuse to the gut wall more slowly and the post-meal glucose rise is blunted.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Increased luminal viscosity slows gastric emptying and impedes convective mixing and diffusion of glucose to the absorptive surface. Gibb et al. measured the clinical consequence and its dependence on starting point: fasting glucose down 37.0 mg/dL and HbA1c down 0.97 percentage points in treated type 2 diabetes, with no significant lowering in euglycaemic subjects.
Bacteria barely touch it, which is why the gel survives to the colon
Most fermentable fibres are consumed by gut bacteria before they get far. Psyllium is not, so it arrives in the colon still holding its water.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Psyllium is a non-fermented or minimally fermented gel-forming fibre. A fermentable gel former loses its water-holding capacity to bacterial metabolism in the proximal colon and cannot deliver a laxative effect there. Non-fermentability is therefore not a limitation of psyllium but the precondition of its stool effect, and it is also why psyllium produces far less gas than fermentable prebiotic fibres.
In the colon the trapped water normalises stool in both directions
The same gel softens hard stool by adding water to it and firms loose stool by holding water inside itself. One mechanism, two opposite-looking results.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
McRorie et al. measured stool water content rising 2.33% on psyllium against 0.01% on docusate, stool water weight 84.0 versus 71.4 g per bowel movement and total output 359.9 versus 271.9 g per week. The bidirectional normalising effect follows from the gel being a water reservoir that neither dissolves nor is fermented away.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
People with chronic constipation, people with irritable bowel syndrome, people with raised LDL cholesterol who want a non-drug option, people with type 2 diabetes, and a large number of people simply trying to eat more fibre.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
Where the result stopped carrying
The soluble-versus-insoluble classification of dietary fibre, replaced by viscosity and fermentability as the properties that predict effect
Bran for irritable bowel syndrome, which produced no benefit across its trials in the pooled analysis
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
The product may not be what it says
Contents of a sold product are not always what the label states.
On this record: This is sold as a supplement, so no agency checked what is in a given tub before it was sold.
Other reasons RNAWiki checked and found nothing for (10)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Varies by country
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Oral powder, granules, wafer or capsule; not absorbed at any point
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Not usually supervised: sold as a supplement or food ingredient where recorded. That is a legal category, not a safety judgement.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
The identity record classes it as a supplement ingredient; no medicines register records an approval.
No source is stored against this line.
What is in the pack
81. 14. Capsules deliver far less psyllium per unit than powder, so reaching the dose used in the lipid trials by capsule requires a large number of them. Product husk purity and particle size affect gel formation and are not standardised across brands.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No register entry is recorded.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Bloating and flatulence, generally less than with fermentable fibres because psyllium is minimally fermented. The specific serious hazard is physical: psyllium swells on contact with liquid, and dry or incompletely hydrated product can obstruct the throat or oesophagus, which is why federal labelling rules apply. It is contraindicated in known bowel obstruction or stricture. Delayed gastric emptying can slow the absorption of medicines taken at the same time. Occupational and, more rarely, ingestion-related IgE-mediated allergy to Plantago ovata is documented, particularly among people handling the powder.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Oral powder, granules, wafer or capsule; not absorbed at any point
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
81. 14. Capsules deliver far less psyllium per unit than powder, so reaching the dose used in the lipid trials by capsule requires a large number of them. Product husk purity and particle size affect gel formation and are not standardised across brands.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
What is recorded as being sold
40 products list this as an active ingredient in the United States drug directory. 39 of them contain it and nothing else.
FDA National Drug Code directory · 37000-024 · read 2026-08-29
They are sold as capsule, granule and powder, taken oral.
FDA National Drug Code directory · 37000-024 · read 2026-08-29
39 published labels name it as an active ingredient. 38 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 2ee637c4-c4c6-4a24-ae99-612205afd592 · read 2026-08-29
Those labels are classed as human otc drug.
US prescribing information · 2ee637c4-c4c6-4a24-ae99-612205afd592 · read 2026-08-29
653 marketed supplement labels list this ingredient, classed as botanical, botanical with nutrients, fiber and other nutrients and other combinations.
Those labels carry all other, approved health and nutrient claims. A claim of that kind is written by the manufacturer and is not assessed by any regulator, so its presence says nothing about whether it is true.
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
Watching one thing carefully can tell you whether it moved. It cannot tell you what moved it.
This is sold without a prescription, so a person can sensibly watch one thing and see whether it moves.
Pick one goal. One goal only. Two at once cannot be told apart afterwards.
Pick one thing to watch. No registered study lists a measure RNAWiki could read for this.
Measure before you start. Take the same measurement several times first. One reading is not a starting point.
Know the swing. Write down how much it moves on its own across a normal week.
Change one thing. Change nothing else at the same time, including training and sleep.
Give it the study length. No finished study window is recorded, so no length is suggested here.
Track whether you took it. Missed days are the most common reason a home test shows nothing.
Read the trend. Look at the line across weeks. A single reading tells you almost nothing.
What not to measure
Anything that swings more day to day than the change you are looking for.
A wearable estimate of sleep stages, which is an estimate and not a measurement.
Weight on one morning, which mostly records water.
A feeling you did not write down before starting.
When to stop
Stop if something new and unpleasant starts, and ask a pharmacist or doctor.
Stop if you cannot keep everything else steady, because the result will not mean anything.
Stop at the end of the window you set, and read the trend then.
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki does not work out an amount for anyone.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That psyllium reduces cardiovascular events, which no trial has tested — the claim rests on the LDL surrogate
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That psyllium evidence transfers to fibre generally, when bran failed in the same IBS analysis and non-viscous soluble fibres fail on lipids and glucose
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That it improves blood sugar in people whose blood sugar is normal, which the pooled data specifically rules out
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
How much did people take in the studies?
The sources RNAWiki checked hold nothing for this field.
Why it matters. A result belongs to an amount. Without the amount the result floats free.
What would answer it
A stored source that records it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Psyllium husk are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
A federal regulation authorises the claim, at a stated dose
In plain words
Almost uniquely for a supplement, the FDA examined the evidence and wrote into federal regulation that psyllium at seven grams of soluble fibre a day can carry a heart disease claim.
What was measured
The daily intake of psyllium soluble fibre the FDA associates with reduced coronary heart disease risk
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
21 CFR 101.81 governs health claims relating soluble fibre from certain foods to a reduced risk of coronary heart disease. It lists the daily dietary intakes of eligible soluble fibre sources associated with reduced risk: 3 g or more per day of beta-glucan soluble fibre from whole oats or barley, and 7 g or more per day of soluble fibre from psyllium seed husk. The regulation also states that "the label and labeling of foods containing psyllium husk shall be consistent with the provisions of § 101.17(f)," the warning provision covering these products, and requires all conditions of 21 CFR 101.14 to be met. Two features of the claim matter for any reader. First, it is conditional on a diet low in saturated fat and cholesterol — the claim is for an adjunct, not a standalone. Second, it is a risk-reduction claim built on the LDL surrogate; no randomised trial has tested psyllium against cardiovascular events.
Source
21 CFR 101.81 — Health claims: soluble fiber from certain foods and risk of coronary heart disease
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
LDL down 0.33 mmol/L across 28 randomised trials
In plain words
Pooling 28 randomised trials in 1,924 people, about ten grams of psyllium a day lowered LDL cholesterol, non-HDL cholesterol and apolipoprotein B.
What was measured
Mean difference in LDL cholesterol, non-HDL cholesterol and apolipoprotein B versus placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Jovanovski and colleagues searched Medline, EMBASE, CINAHL and CENTRAL through October 2017 for randomised controlled trials of at least three weeks assessing psyllium and blood lipids, in people with or without hypercholesterolaemia. Twenty-eight trials with 1,924 participants were included. A median dose of about 10.2 g psyllium per day significantly reduced LDL cholesterol by 0.33 mmol/L (95% CI -0.38 to -0.27, P < 0.00001) and non-HDL cholesterol by 0.39 mmol/L (95% CI -0.50 to -0.27, P < 0.00001), with apolipoprotein B also reduced. The earlier Anderson meta-analysis of 8 controlled trials, in 384 psyllium and 272 cellulose-placebo subjects all taking 10.2 g/day for at least 8 weeks on top of at least 8 weeks of low-fat diet lead-in, found total cholesterol down 4% (P < 0.0001), LDL down 7% (P < 0.0001) and the apoB to apoA-I ratio down 6% (P < 0.05), with no effect on HDL or triglycerides. The two analyses, eighteen years apart, agree closely, which is more than can be said for most of this file.
Written into the record, not signed off as a reviewed claim
It beat docusate sodium head-to-head on every objective stool measure
In plain words
In 170 people with chronic constipation, psyllium outperformed a standard over-the-counter stool softener on stool water content, stool weight, total output and bowel movement frequency.
What was measured
Stool water content and weight, total stool output, and bowel movements per week
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A multi-site, randomised, double-blind, parallel-design trial in 170 subjects with chronic idiopathic constipation ran a two-week placebo baseline then two weeks comparing psyllium 5.1 g twice daily plus docusate placebo against docusate sodium 100 mg twice daily plus psyllium placebo, with stools collected and assessed. Against baseline, psyllium increased stool water content by 2.33% versus 0.01% for docusate (P = 0.007), stool water weight to 84.0 against 71.4 g per bowel movement (P = 0.04), total stool output to 359.9 against 271.9 g per week (P = 0.005), and the O'Brien rank-type composite score to 475.1 against 403.9 (P = 0.002). Bowel movement frequency was significantly greater on psyllium in treatment week two (3.5 versus 2.9 per week, P = 0.02) but not in week one (3.3 versus 3.1, P > 0.05). These are objective, collected, weighed measurements rather than symptom questionnaires, which is unusual and is what makes the result credible.
Written into the record, not signed off as a reviewed claim
The glycaemic benefit is proportional to how bad the glucose control already is
In plain words
Psyllium improved blood sugar substantially in people with type 2 diabetes, modestly in people at risk, and not at all in people whose glucose was already normal.
What was measured
Change in fasting blood glucose and glycated haemoglobin, stratified by baseline glycaemic status
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Gibb and colleagues identified 35 randomised controlled studies spanning three decades and three continents, assessed in 8 meta-analyses. In patients with type 2 diabetes, multi-week studies with psyllium dosed before meals showed fasting blood glucose down 37.0 mg/dL (P < 0.001) and HbA1c down 0.97 percentage points, or 10.6 mmol/mol (P = 0.048). The effect was proportional to baseline fasting glucose: no significant glucose lowering in euglycaemic subjects, modest improvement in pre-diabetes, greatest improvement in treated type 2 diabetes. That gradient is the finding, and it is the same repletion-shaped pattern that runs through this whole file — the intervention does most where the deficit is largest and nothing where there is no deficit. The conflict belongs on the record: the search covered "clinical records stored by Procter & Gamble", the manufacturer of the leading psyllium brand, alongside the published literature, and the authors are associated with that company. An HbA1c reduction of nearly a full percentage point is close to what some glucose-lowering drugs achieve, which makes the provenance of the pooled dataset something a reader should weigh.
Written into the record, not signed off as a reviewed claim
IBS: soluble fibre worked, bran did not, and the difference is the point
In plain words
Across fourteen randomised trials in irritable bowel syndrome, soluble fibre helped and wheat bran did not. Roughly one in seven people benefited from soluble fibre.
What was measured
Relative risk of remaining symptomatic after fibre therapy, and number needed to treat
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Moayyedi and colleagues searched MEDLINE, EMBASE and the Cochrane Controlled Trials Register to December 2013 for trials comparing fibre supplements against placebo, control therapy or usual management in adults with irritable bowel syndrome. Fourteen randomised trials in 906 patients were identified. Overall there was a significant benefit of fibre (relative risk of remaining symptomatic 0.86, 95% CI 0.80 to 0.94; number needed to treat 10, 95% CI 6 to 33), with no significant heterogeneity (I-squared 0%, Cochran Q 13.85 with 14 degrees of freedom, P = 0.46). The benefit was confined to soluble fibre (RR 0.83, 95% CI 0.73 to 0.94; NNT 7, 95% CI 4 to 25), with no effect from bran (RR 0.90, 95% CI 0.79 to 1.03). The authors found no evidence of harm from bran but also no benefit. The clean separation between two things both called fibre, in the same analysis, is the strongest single argument against treating fibre as a category.
Written into the record, not signed off as a reviewed claim
The field stopped talking about soluble versus insoluble, and started talking about viscosity
In plain words
Fibre was long divided into soluble and insoluble as though that predicted its effects. It does not. What predicts them is whether the fibre forms a thick gel and whether bacteria eat it.
What was measured
That "soluble fibre" is a functional category whose members share clinical effects
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
McRorie and McKeown set out the reclassification directly. Clinically meaningful small-bowel benefits — cholesterol lowering and improved glycaemic control — are highly correlated with viscosity: high-viscosity gel-forming fibres such as beta-glucan, psyllium and raw guar gum produce them, while non-viscous soluble fibres such as inulin, fructooligosaccharides and wheat dextrin do not. In the large bowel only two mechanisms drive a laxative effect: coarse insoluble particles mechanically irritating the mucosa and stimulating water and mucus secretion, and the high water-holding capacity of a gel-forming soluble fibre. Psyllium sits in the second group and is additionally almost entirely unfermented, so its gel is still holding water when it reaches the colon — a fermentable gel-former loses its water-holding capacity to the bacteria before it gets there. This reframing explains why "add more fibre" produces such inconsistent clinical results, and why psyllium's evidence does not transfer to most of the fibre aisle.
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What is not here
7 questions this page could not answer
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The record as stored
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The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
Psyllium lowers LDL cholesterol by about 0.33 mmol/L across 28 randomised trials, softens stool and increases output more than docusate did head-to-head, and holds an authorised FDA heart-disease health claim at 7 g/day of soluble fibre — with the caveats that much of the pooled evidence was assembled by scientists at the company selling the leading brand, and that its glycaemic effect is zero in people whose glucose is already normal.
Which one trial of Psyllium husk posted no result?
Posted no result
1 of 1 completed trials
Registrations
NCT05867550
Completion dates
oldest 2023-06-10
Show the evidence
TrialNCT05867550
2023-06-10
Q4
At the median, Psyllium husk's trials enrolled 42 people — anything larger?
Median enrolment
42
Largest enrolment
162
Registered trials counted
4
Q5
What do 71 spontaneous reports say about Psyllium husk — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Psyllium husk appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 71 reaction mentions were counted: fatigue 13; constipation 11; drug hypersensitivity 9; cerebrovascular accident 7. FAERS via Open Targets · CHEMBL2108126 · 2026-06-24
Show the evidence
fatigue
13
constipation
11
drug hypersensitivity
9
cerebrovascular accident
7
confusional state
7
crohn's disease
5
4 more recorded rows
oropharyngeal pain
5
speech disorder
5
vision blurred
5
anal incontinence
4
recorded 2026-06-24 · last checked 2026-09-04
Where it is registeredIdentifiers, relations and other names
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✓ source coverage passed: 3 source rows
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