What it is
Psyllium is the husk and the seed of Plantago ovata. Its soluble fibre swells on contact with water and forms a viscous gel that increases stool volume and slows whatever passes through with it. People buy it for constipation, LDL cholesterol, blood sugar and satiety.
What the label does not say
- The cholesterol claim is quantified: Health Canada (December 2011 decision, 21 human studies) reserves it for foods providing at least 1.75 g of psyllium soluble fibre per serving, on the basis of 7 g per day. A serving that does not show its grams of psyllium soluble fibre cannot be compared with that dose.
- The effect on LDL is real and modest: 0.33 mmol/L lower (confidence interval 0.27 to 0.38) at a median dose of about 10.2 g per day in the meta-analysis of 28 trials (1,924 participants).
- The water is not a suggestion. Health Canada requires "for each dose, drink at least 250 mL of liquid" and contraindicates the product in case of difficulty swallowing; U.S. regulations impose a notice of possible choking without enough liquid, and the EMA describes a risk of esophageal or intestinal obstruction, ruling out taking it just before bedtime.
- The gel slows the absorption of whatever is swallowed at the same time. Health Canada asks you to take it "a few hours before or after" other medications and health products; the EMA retains a half hour to one hour apart and monitoring with thyroid hormones and antidiabetics.
The forms on the shelf
- Powdered husk: the form used in the trials. The Health Canada monograph doses it at 2.5 to 30 g per day in adults, maximum 8 g per dose; the seed, at 2.5 to 40 g per day, maximum 13 g per dose.
- Capsules: the same fibre, but the EMA's 7 to 11 g per day requires many capsules, with the same liquid requirement.
- "Fibre" blends (inulin, acacia gum, wheat dextrin, methylcellulose): these fibres do not carry psyllium's data on LDL, and the Canadian health claim targets psyllium soluble fibre.
Published reference values
- No recommended intake specific to psyllium; the NIDDK puts total fibre at 22 to 34 g per day in adults depending on age and sex.
- Non-HDL cholesterol and apoB: 0.39 mmol/L and 0.05 g/L lower in the same 2018 meta-analysis.
- Blood sugar: in a meta-analysis of 35 trials, psyllium taken before meals lowers fasting glucose by 37 mg/dL (about 2 mmol/L) and HbA1c by 0.97 points in people with type 2 diabetes, little in prediabetes, not at all with normal blood sugar.
- Transit: effect observed 12 to 24 hours after the first dose, sometimes 2 to 3 days, according to Health Canada. Expected effects: temporary gas and bloating.
When
Before meals when the goal is blood sugar (that is how the trials dosed it), always with at least 250 mL of liquid drunk immediately, and not just before bedtime. The NIDDK advises increasing fibre little by little, which limits gas and bloating.
Keep apart from
- All medications and health products: "a few hours" apart according to Health Canada, a half hour to one hour according to the EMA.
- Thyroid hormones, antidiabetics and insulin: monitoring requested by the EMA (altered absorption or effect).
- Lithium, carbamazepine, cardiac glycosides such as digoxin, coumarin derivatives, minerals and vitamin B12: absorption possibly reduced according to the EMA.
To mention to a professional
- Difficulty swallowing, fever or undiagnosed digestive disorder (contraindications), intestinal narrowing or obstruction, sudden change in bowel habits lasting more than 2 weeks, unexplained rectal bleeding, diabetes, pregnancy and breastfeeding: check with a health care professional. Chest pain, vomiting or difficulty swallowing or breathing after taking it: seek care immediately.
From the plate first
Psyllium is not something you eat from your plate; it adds to the NIDDK's 22 to 34 g of daily fibre.
Sources
- Health Canada, natural health product monograph, Psyllium
- Health Canada, Psyllium products and blood cholesterol lowering, summary of a health claim assessment
- Jovanovski et al., Effect of psyllium (Plantago ovata) fiber on LDL cholesterol and alternative lipid targets, American Journal of Clinical Nutrition (meta-analysis, 2018)
- Gibb et al., Psyllium fiber improves glycemic control proportional to loss of glycemic control: a meta-analysis, American Journal of Clinical Nutrition (2015)
- European Medicines Agency (EMA), Community herbal monograph on Plantago ovata Forssk., seminis tegumentum
- FDA, 21 CFR 101.17(f), Foods containing psyllium husk (labelling notice)
- NIDDK, Constipation, Eating, Diet and Nutrition
Educational information, drawn from the sources above. It does not replace the advice of a health professional, who remains the reference for your situation, your medications, pregnancy or breastfeeding.