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Psyllium (usually as husk or powder) is a fiber derived from the plant Plantago psyllium that is able to bind to fatty acids and cholesterol from the diet; it can increase fecal moisture and weight.

Our evidence-based analysis on psyllium features 103 unique references to scientific papers.

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Summary of Psyllium

Primary information, health benefits, side effects, usage, and other important details

Psyllium is the common word used to refer to fibers taken from the plant known as Plantago ovata (Plantago psyllium is used synonymously, and is where the fiber name is derived from); the fiber is characterized by being water soluble (hydrophilic) and gel forming, while possessing low fermentability. It is commonly known by the brand name Metamucil.

Psyllium is used clinically as a bulk laxative, an agent that has laxative effects but secondary to increasing fecal size; a gentler laxative relative to chemical agents like caffeine or senna alexandrina. This bulk occurs due to water and gas absorption in the small intestines and colon to give chyme (made from digested food) more size and softness. This bulk is retained in the colon despite microflora as psyllium is poorly fermented (highly fermented fibers may be metabolized by bacteria in the colon, and water retaining properties with the fiber would be lost in this scenario).

Psyllium is proven to increase fecal size and moisture, and the most common characteristics of stool following supplementation of psyllium are 'soft, sleek, and easily passable.' Relative to other sources of dietary fiber, psyllium appears to be more effective at forming feces and appears to be one of the few fiber sources not associated with excessive flatulence.

Beyond the fecal properties, psyllium appears to be able to reduce total cholesterol and LDL cholesterol in persons with high cholesterol (secondary to the gel forming properties leeching bile acids, and cholesterol being used up to replace hepatic bile acids) and there is a slight reduction of HDL as well. This is common to all dietary fibers and is not unique to psyllium.

There appears to be some glucose reducing properties associated with psyllium supplementation that may benefit diabetics. These are not overly potent, but appear reliable as long as psyllium is taken; cessation of psyllium usage is associated with a loss of the glucose reduction, and this may be common to all soluble dietary fibers rather than just psyllium.

Psyllium may reduce appetite slightly when taken in high doses, but does not appear to be potent or reliable; long term studies using psyllium in the doses for fecal management have failed to find weight reducing properties of psyllium suggesting it is not a good weight management intervention.

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How to Take

Recommended dosage, active amounts, other details

On the lower end of dosing, 5g of psyllium is taken once with meals alongside some form of liquid (200mL of water or more) and can be taken at every meal if desired; coingestion of psyllium with a meal is not mandatory although coingestion with water is highly advised.

Acute doses of up to 30g appear to be well tolerated assuming enough water (in these instances, around 500mL or so) are also coingested.

If using psyllium for the fecal forming properties, a daily dose of 15g (thrice daily dosing of 5g) is a good starting point and then the dose can be titrated up or down depending on its effects on fecal formation.

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Human Effect Matrix

Unlocked for Examine members

The Human Effect Matrix summarizes human studies to tell you what effects Psyllium has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
grade-a Minor Very High See all 6 studies
Not overly potent reductions of LDL-C, although they seem to reliably occur in persons with high cholesterol
grade-b Minor Very High See all 4 studies
Reductions in blood glucose seen with psyllium seem to occur reliably in persons with high blood glucose, but are transient benefits and not of a remarkable magnitude.
grade-b Minor Very High See all 3 studies
Similar to the reductions in LDL-C and total cholesterol, the reduction in HDL-C is seemingly small in magnitude and likely not much to be concerned about
grade-b Minor Very High See 2 studies
Reduction seen in HbA1c was not overly remarkable
grade-b Minor Very High See all 4 studies
Not unique to psyllium, but has the standard slight reduction of cholesterol that affects persons with high cholesterol. Not strong enough for monotherapy, can be a nice addition to more potent supplements or drugs
grade-b - High See all 3 studies
No real significant effect of psyllium on blood pressure directly, although there may be an insignificant reduction seen with correcting other parameters of metabolic syndrome.
grade-b - Very High See all 4 studies
Currently, it does not seem like there is a significant influence of psyllium on circulating triglycerides
grade-b - Very High See all 4 studies
No convincing evidence for a weight reducing effect of psyllium.
grade-c Strong Very High See all 4 studies
Psyllium is the reference drug for increasing water content of stool.
grade-c Strong Very High See all 4 studies
Psyllium tends to be the reference drug for increasing fecal weight, and due to that and the reliability of which this occurs it gets a strong rating
grade-c Minor Very High See all 3 studies
Studies that report appetite note that there is a significant reduction after a meal containing psyllium (relative to no fiber ingestion) although it does not appear to be too remarkable in potency as overall food intake does not appear influenced.
grade-c Minor - See study
Study noted an improved augmentation index by 22% alongside a reduction in blood pressure, mechanisms unknown and no reference drug for comparison.
grade-c Minor - See study
Supplementation of 12g psyllium husk with a test breakfast is able to reduce carbohydrate absorption by around 12% relative to control.
grade-c Minor - See study
A decrease in fructosamine has been noted in diabetics supplementing psyllium husk.
grade-c Minor Moderate See 2 studies
A minor decrease in diabetics following supplementation, although it is small in magnitude and does not carry over to nondiabetics.
grade-c Minor - See study
No reference drug to compare it to, and thus the potency in psyllium delaying gastric emptying is not certain.
grade-c Minor - See study
An 11% decrease in uric acid has been noted in diabetics supplementing with psyllium husk.
grade-c - - See study
No significant alterations of insulin sensitivity in those who are not insulin resistant at baseline
grade-c - Very High See 2 studies
No significant influence on iron absorption; it is possible the inhibitory effect of phytates in the small intestine are negated by the reduced pH in the colon that enhances mineral reuptake
grade-d Notable - See study
Notably effective as dietary fibers should normally enhance flatus (almost being a 'per se' effect of dietary fiber) yet psyllium has noted the opposite effect.
grade-d Notable - See study
The potency of psyllium husk in controlling remission of ulcerative colitis is comparable to the reference drug mesalamine.
grade-d Minor - See study
Increases intestinal motility due to being a bulk laxative, but is unlikely to have a strong laxative effect.
grade-d - - See study
Failed to significantly influence food intake
grade-d - - See study
A significant reduction of lipid absorption (assessed via fecal lipids) is not yet supported.
grade-d - - See study
Failed to modify the thermic effect of food.

Studies Excluded from Consideration

  • Confounded with inclusion of carbohydrates in test wafers[1]

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Things to Note

Is a Form Of

Primary Function:

Also Known As

Psyllium Husk, Psyllium Fiber, Metamucil (brand name), ispaghula, plantago psyllium, plantago ovata, plantago

Goes Well With

  • Compounds requiring stomach exposure (increases exposure of said drug to the stomach, and may be useful for augmenting anti-ulcer agents)

Caution Notice

Psyllium should be taken with water acutely, and placement of psyllium powder or husk into the mouth without water may result in sapping of saliva and subsequent choking.

  • Psyllium can be bought in husks or powder, with no significant difference between either option for the most commonly used purposes of psyllium

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Click here to see all 103 references.