Also known as: Plantago ovata, Ispaghula, Psyllium fibre, Isabgol
FoundationalStrong evidence
Soluble fibre from the husk of Plantago ovata seeds, and one of the few supplements in this index with genuinely strong evidence across several outcomes. Cheap, unglamorous and it works.
Typical dose
5.0–10.0 g per day
With a large glass of water; separate from medication by 2 hours
What it is
Psyllium is the husk surrounding the seeds of Plantago ovata, a plant grown mainly in India. It is roughly 70 per cent soluble fibre, which is unusually high.
What makes it distinctive is that it forms a viscous gel in water rather than simply adding bulk. That gel-forming property is the mechanism behind most of what it does, and it is why psyllium behaves differently from bran or other insoluble fibres.
It is also unusual among fibres in being only partially fermented by gut bacteria. Highly fermentable fibres like inulin produce gas; psyllium largely does not, which makes it far better tolerated by people with sensitive digestion.
How it works
In water psyllium forms a gel that holds many times its weight. In the gut that gel adds bulk and water to stool, softening it and making it easier to pass, while also slowing transit when things are moving too fast.
That dual action is unusual: the same substance helps in both directions, which is why psyllium is recommended for opposite problems.
The gel also binds bile acids in the intestine, forcing the liver to make more from cholesterol, which is the mechanism behind the lipid effects. And by slowing gastric emptying and carbohydrate absorption, it flattens the blood glucose rise after a meal.
What the evidence shows
Bowel regularity is thoroughly established, with consistent evidence across many trials for both stool frequency and consistency.
The cholesterol evidence is genuinely strong. Meta-analyses consistently report reductions in total and LDL cholesterol with daily psyllium, and this is one of the better-evidenced effects of any supplement in this entire index.
There is also good evidence for flattening post-meal blood glucose, and reasonable evidence for increased satiety and modest effects on body weight. For a cheap kitchen-cupboard product, the evidence base is remarkable, and it is considerably better than most things sold at ten times the price.
Dosing
Start at 3 to 5 g daily and build to 10 g or more, split across servings. Building up gradually matters, as with any fibre.
Fluid is not optional. Psyllium must be taken with a large glass of water and followed by more, and it should be drunk immediately after mixing because it thickens within a minute or two. Taking it with insufficient fluid is the one way to genuinely cause yourself trouble with it.
Take it away from medication and from other supplements by at least two hours, since the gel can reduce absorption of things taken alongside it. For blood glucose purposes, take it just before a carbohydrate-containing meal.
Acts throughout transit; lipid effects accrue over weeks
Timing
With a large glass of water; separate from medication by 2 hours
Competition status
Permitted — not on the WADA Prohibited List
Category
Foundational
Safety and side effects
Psyllium is well tolerated and better suited to sensitive digestion than fermentable fibres, since it produces little gas. Bloating in the first week is common and settles.
The one genuine hazard is taking it with too little fluid. Psyllium expands rapidly, and taken dry or with a small amount of liquid it can cause choking or obstruction. Always take it with a full glass of water and drink it promptly.
Anyone with difficulty swallowing, or who has been told they have a narrowing anywhere in the digestive tract, should not take it. Separate from medication, since it can reduce absorption.
Who should avoid it
Always take with a full glass of water and drink promptly — taken dry or with insufficient fluid it can cause choking or obstruction. Avoid if you have difficulty swallowing or have been told there is a narrowing anywhere in your digestive tract. Separate from all medication by at least two hours, since it reduces absorption. Build the dose up gradually.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
