Ingredient
Psyllium Husk
A soluble fibre from Plantago seed with a real and moderate LDL effect, and no reliable effect on triglycerides or HDL.
Psyllium is the husk of Plantago ovata seed, sold as a soluble fibre and used mainly for cholesterol and bowel regularity. It is one of the few supplement ingredients where the lipid effect is large enough and consistent enough to survive a pooled analysis.
What the trials measured
| Outcome | Effect | 95% CI | Trials | Grade |
|---|---|---|---|---|
| LDL cholesterol | −0.33 mmol/L at ~10.2 g/day | −0.38 to −0.27 | 28 RCTs | B |
| Non-HDL cholesterol | −0.39 mmol/L | −0.50 to −0.27 | Same 28 RCTs | B |
| Apolipoprotein B | −0.05 g/L | −0.08 to −0.03 | Same 28 RCTs | B |
| Total cholesterol | −9.05 mg/dL | −13.71 to −4.40 | 41 RCTs, n=2,049 | C |
| Triglycerides | −5.29 mg/dL | −12.14 to +1.54 | Same 41 RCTs | C |
| HDL cholesterol | +0.57 mg/dL | −0.88 to +2.04 | Same 41 RCTs | C |
Three of these six rows are graded C, and the reason is not that the effect is small — it is that the interval does not exclude zero. The triglyceride and HDL rows cross zero outright. The total cholesterol row is graded C because heterogeneity (I² = 89%) is too high for the pooled figure to describe any one dose or product.
The effect is real but narrow
LDL falls; triglycerides and HDL do not. A page that says psyllium “improves cholesterol profile” is describing one of three markers accurately and the others not at all. The distinction matters when comparing it to a statin, or to another fibre.
Gas is the predictable trade-off
The same trials that measured stool frequency measured flatulence, and psyllium increased it: SMD 0.80 (95% CI 0.47 to 1.13) above control, on the same 16 trials where stool frequency improved. Patients notice this. It is the most common reason people stop taking it.
The real hazard is not gas
Taken dry, or with too little fluid, psyllium swells before it clears the throat. The published obstruction and choking cases, and the fluid rules that follow from them, are documented in the psyllium side effects guide.
Psyllium versus a branded product
Metamucil is psyllium with added sugar, colour, or flavour, in formats that differ in dose per serving. The trial evidence belongs to psyllium the fibre, not to a particular box. What changes between products is the dose per scoop, what else the scoop contains, and how you take it — worked through in psyllium vs Metamucil.
Facts checked: 29 October 2026 · VitalRoundup Editorial Team · How we review