Soluble fibre (barley first)

Gel-forming fibre from barley, oats or psyllium. It lowers LDL cholesterol a little and helps raised blood sugar. Claims that it clears chemicals from the body rest on very weak evidence.

At a glance

Our verdict	Lowers LDL a little, and helps blood sugar when it is raised. Barley beta-glucan first; oat beta-glucan if avoiding gluten; psyllium only with published heavy-metal results.
Best use	Cholesterol and blood sugar
How sure the evidence is	Moderate for LDL; Very low for chemicals
Cost a month	About $47 to $64 (barley beta-glucan product); oats $5 to $10

Written for adults in Canada. It explains the evidence; it is not advice for you personally. Last reviewed 20 October 2026.

Supplement Check

Is it right for you?

Fibre suits most people, but whether it is the right step for you depends on your LDL, your blood sugar, your gut and the medicines it must be spaced from. Your check looks at all of it, and says when a medicine would do more. Our Supplement Check looks at:

Difficulty swallowing, a narrowing of the gullet or bowel, a previous bowel blockage, a slow-emptying stomach (gastroparesis), or recent bowel surgery
A doctor has told you to limit fluids
Coeliac disease or gluten sensitivity
Diabetes treated with insulin or a sulfonylurea
LDL of 5.0 mmol/L or more, or a condition where a statin is advised and none is taken
Every medicine you take

Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.

$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check

Tell me when it opens

What it is

Soluble fibre is the kind that forms a gel in water. The main forms are beta-glucan from barley or oats, and psyllium husk.

Dr. French's order: barley beta-glucan first; oat beta-glucan from certified gluten-free (purity-protocol) oats for anyone avoiding gluten; psyllium only from a brand that publishes its heavy-metal test results, because psyllium can carry lead and arsenic.

About the barley product, honestly. It is sold in Canada as a food, not as a licensed natural health product, so it has no NPN. The grams of beta-glucan per serving are not printed (about 1 g per tablespoon, worked out from the maker's own figures), and the maker does not publish heavy-metal or mould-toxin results. It “contains trace amounts of gluten because it's extracted from barley” (maker's words), so it is not for anyone who must avoid gluten. We have not yet named an oat beta-glucan product, and on 14 Oct 2026 we found no psyllium brand in Canada that publishes its heavy-metal results.

Structure of Soluble fibre (barley first) — Structure: PubChem (public domain).

How it acts

In the gut the gel slows the absorption of sugar, and it binds bile acids so they leave in the stool. The liver then uses cholesterol to make new bile, and LDL falls. This effect depends on the fibre being thick (high molecular weight): oat bran with native beta-glucan raised bile acid loss by 144% in 9 people with an ileostomy, [1] and 3 g of high-molecular-weight barley beta-glucan raised bile acid production, while a low-molecular-weight form, even at 5 g, did not. [2, 3]

Anything carried in bile can in theory be carried out with it, including some long-lasting chemicals. That is the mechanism behind the “binding” claims; it has been shown for prescription resins, not for fibre (see below).

Diagram: how Soluble fibre (barley first) acts

Outline of a person showing where Soluble fibre (barley first) acts in the body

What it is used for, and what the evidence says

Use	What the trials found	How sure we are
LDL cholesterol, barley beta-glucan	14 trials, 615 people, a median of 6.5 g a day: LDL 0.25 mmol/L lower. Apolipoprotein B (the number of LDL-type particles) did not change significantly. [4]	Moderate
LDL cholesterol, psyllium	28 trials, 1,924 people, about 10 g a day: LDL 0.33 mmol/L lower, non-HDL cholesterol 0.39 lower, apolipoprotein B 0.05 g/L lower. [5]	Moderate
Blood sugar in type 2 diabetes	Viscous fibre, 28 trial comparisons, 1,394 people, about 13 g a day on top of usual care: average blood sugar (HbA1c) 0.58% lower, fasting glucose 0.82 mmol/L lower. [6] Psyllium: HbA1c 0.97% lower in diabetes, a modest effect in prediabetes and none with normal blood sugar; this review was written by employees of the maker of Metamucil. [7]	Moderate
Blood sugar, oat or barley beta-glucan extracts	Oat beta-glucan 2.5 to 3.5 g a day, 4 short trials, 350 people with diabetes: HbA1c 0.21% lower. [8] Across 18 trials, whole oats and oat bran lowered HbA1c, but oat or barley beta-glucan extracts did not reach significance. [9] That matters for the barley product we use, which is a barley extract.	Low
Triglycerides	Neither the barley nor the psyllium reviews found a fall. [4, 5] In diabetes, a network review ranked other fibres (guar, fenugreek), not beta-glucan or psyllium, for triglycerides. [10] We do not recommend fibre for triglycerides.	Very low
Long-lasting chemicals (PFAS, pesticides)	The “binding” idea is proven for prescription resins: cholestyramine halved the time the pesticide chlordecone stayed in the blood of 22 poisoned workers (165 to 80 days), [11] and 12 weeks of colesevelam lowered blood PFOS by 38% against 2% in 10 highly exposed adults. [12] For fibre itself, the only study in people is an exploratory analysis of a 4-week trial in 72 Canadian men: total PFAS fell in both groups, and long-chain PFAS fell only in the oat beta-glucan group; the difference between groups was not reported. [13] In a US survey, people eating more fibre had 4 to 8% lower PFAS levels, but that is an association, not proof. [14]	Very low (fibre)
Heavy metals and mould toxins	No study of oat or barley beta-glucan. One good trial of a different fibre (inulin 10 g a day) in 29 people on dialysis lowered blood arsenic by 1.03 µg/L from a starting level of 3.5. [15] No study in people of any fibre against mould toxins.	Very low to none
Heart attacks, strokes, deaths	No trial of a fibre supplement has measured them. In long-term studies, people eating more fibre from food had 15 to 30% lower death rates, less heart disease, type 2 diabetes and bowel cancer. [16]	Low (food fibre)

How sure we are: High means further research is very unlikely to change the answer; Moderate, it might; Low, it may well change; Very low, we are very unsure. These follow the GRADE method that guideline panels use.

Benefits

LDL cholesterol: 0.25 to 0.33 mmol/L lower (about 5 to 10%); Moderate
HbA1c, type 2 diabetes: 0.2 to 0.6% lower; Moderate
HbA1c, normal blood sugar: No change; Moderate
Triglycerides: Not shown; Very low
PFAS and other long-lasting chemicals: Possible small help; not measured properly; Very low
Heavy metals, mould toxins: Not shown; Very low to none

Risks and side effects

Gas and bloating. Start low and build up.
Blockage of the gullet or bowel if taken without enough water, especially with swallowing problems, Parkinson disease, a previous bowel narrowing or a gastric band (case reports with psyllium).
Allergy to psyllium, mostly in people who handle it at work.
Heavy metals in psyllium, which is why we use only a brand that publishes its results.
Gluten: the barley product contains traces.

Interactions with medicines

Fibre does not change how the liver clears medicines. Its interactions come from slowing or reducing absorption in the gut, and from lowering blood sugar.

Medicine	What can happen	What to do
Most tablets and capsules	Less absorbed if taken together	Take other medicines at least 2 hours before or after
Levothyroxine	Less absorbed	Space by 4 hours
Lithium, digoxin, carbamazepine, warfarin	Small changes in absorption matter for these	Blood level or INR checked after starting
Insulin, gliclazide, glyburide, glimepiride	Blood sugar may fall too far	Held for a doctor

Who should not take it

Difficulty swallowing, a narrowing of the gullet or bowel, a previous bowel blockage, a slow-emptying stomach (gastroparesis), or recent bowel surgery.
A doctor has told you to limit fluids.
Coeliac disease or gluten sensitivity: not the barley product; oat beta-glucan from purity-protocol oats instead (most people with coeliac disease tolerate these; a minority react to oats).
Diabetes treated with insulin or a sulfonylurea: a doctor first.
LDL of 5.0 mmol/L or more, or a condition where a statin is advised and none is taken: see a doctor; fibre is not a substitute.
Older adults: split the dose and take it with a full glass of fluid.
Pregnancy and breastfeeding: no concern from fibre itself.
Under 18: outside the Supplement Check.

Dose and timing

Barley beta-glucan product: 3 tablespoons a day for about 3 g of beta-glucan, the amount behind Health Canada's cholesterol claim. Start with 1 tablespoon a day for a week. Mix in at least 250 mL of fluid and split across meals.
Avoiding gluten: oat beta-glucan from purity-protocol oats, 3 g a day.
Psyllium (only a brand with published heavy-metal results): 7 g of soluble fibre a day for LDL (about 10 g of husk), each dose with 250 mL of water; before meals when the aim is blood sugar.
For chemicals: no dose is established. The only study used oat beta-glucan with each meal for 4 weeks. [13]
Space other medicines by 2 hours (levothyroxine 4 hours).
How to tell it is working: LDL (with non-HDL cholesterol or apolipoprotein B) at 6 to 12 weeks, expecting about 0.25 to 0.33 mmol/L lower; HbA1c at 3 months if your blood sugar is raised. There is no practical test for chemical binding.
Food first: oats, barley, beans, lentils, vegetables and fruit every day.
Store sealed, cool and dry.

What we know about Canadians

Almost no one in Canada eats enough fibre. In the 2015 national nutrition survey, men averaged 18.4 g a day and women 16.2 g, against targets of 38 g and 25 g (30 g and 21 g after 50). Only 1 to 6% of men and 4 to 22% of women reached the target. [17] These figures count fibre naturally present in food only, so true intake is slightly higher, but not by enough to change the picture.

Most at risk: nearly everyone; men most; diets low in whole grains, legumes, vegetables and fruit.

How sure are we: moderate. National survey, but based on recalled food and 11 years old.

An honest comparison: LDL cholesterol

The same outcome, in the same units, with the cost a month in Canadian dollars.

Option	Effect	How sure we are	Cost a month (CAD)
Psyllium about 10 g a day (published heavy-metal results only)	LDL 0.33 mmol/L lower [5]	Moderate	$10 to $20
Barley beta-glucan product	LDL 0.25 mmol/L lower [4]	Moderate	$47 to $64
Portfolio eating (oats or barley, nuts, soy, plant sterols together)	LDL 0.73 mmol/L lower (about 17%) [18]	High	Food roughly neutral; dietitian about $30
Statin, moderate dose (atorvastatin 10 mg, generic)	LDL 1.8 mmol/L lower (40%) from 4.8 [19]	High	$10 to $20
Ezetimibe 10 mg	LDL 18.6% lower [20]	High	$15 to $25

Read honestly: for LDL, a statin does 6 to 7 times what fibre does, at about a third of the barley product's monthly cost. Fibre is an add-on, or a choice for people below the point where a statin is advised. For blood sugar in type 2 diabetes, viscous fibre does about half of what metformin does (HbA1c about 1.1% lower); [21] beta-glucan extracts do much less.

Our verdict

For adults with a raised LDL cholesterol below the level where a statin is advised, or with raised blood sugar (prediabetes or type 2 diabetes), alongside food: barley beta-glucan first, oat beta-glucan if you avoid gluten, psyllium only from a brand that publishes heavy-metal results. For smokers and people exposed to fumes at work it is part of the package with sulforaphane and sauna, with the honest wording: it may help the body clear some long-lasting chemicals; it has not been shown to remove them, nor heavy metals or mould toxins.

Not for triglycerides, not for normal blood sugar, and not instead of a statin or metformin when one is advised.

Soluble fibre carries bile out of the body, which is how it lowers cholesterol, and it has moderate-certainty evidence for a small fall in LDL and in raised blood sugar. It is cheap as food and safe for most people. Medicines do more, and we show that side by side. Prescription resins that work the same way speed the removal of some long-lasting chemicals, such as PFOS; for fibre itself that has only been tested in small, early studies, so we say “may help”, never “removes”. Dr. French's order (barley first, oat beta-glucan for gluten avoiders, psyllium only with published heavy-metal results) puts purity and gluten first. It is worth taking for cholesterol and blood sugar anyway, and that is the main reason we recommend it.