plant sterol
Meaning of plant sterol: The active ingredient in cholesterol-lowering spreads, backed by a measurable drop in LDL but not by proof of fewer heart attacks.
Definition of plant sterol
A plant sterol is a fat-like compound made by plants that closely resembles cholesterol in shape but is barely absorbed by the human gut. Present naturally in vegetable oils, nuts, seeds and grains, it competes with cholesterol for a place in the mixed droplets the intestine takes up, so less cholesterol reaches the bloodstream. Concentrated forms are added to spreads and supplements.
How does it lower cholesterol?
Most of the cholesterol arriving in the intestine never came from food. The liver pours far more into the gut in bile than a meal delivers, and much of that is reabsorbed. Before any of it can cross the gut wall it has to be packaged into tiny mixed droplets. A plant sterol fits into those droplets as readily as cholesterol does, but is then rejected at the cell surface and pumped straight back out. It takes up space in the queue and leaves less room, so a share of the cholesterol passes on through and is lost in the stool. The level of low-density lipoprotein in the blood, the fraction usually called bad cholesterol, falls modestly as a result. Laboratory reports and ingredient lists often use the word phytosterol for the same class of compound.
What does the evidence support?
The fall in low-density lipoprotein is consistent across trials, which is why several countries permit a cholesterol-lowering claim on enriched foods. What has never been shown is the step that matters more: that the people eating them go on to have fewer heart attacks or strokes. No study has been large enough or long enough to answer that. Claims about cancer prevention rest on cell and animal work rather than results in people.
How do sterols and stanols compare?
| Form | Main sources | Absorbed by the gut |
|---|---|---|
| Plant sterol | Vegetable oils, nuts, seeds, grains | Very little |
| Plant stanol | Made from sterols; traces in cereals and wood pulp | Almost none |
| Cholesterol | Animal foods and the body's own bile | Readily |
Both plant forms lower cholesterol to a similar degree, and the choice between them in a product is largely commercial. Two cautions attach to the class. Enriched foods reduce the uptake of beta carotene and other fat-soluble plant pigments alongside the cholesterol. And in a rare inherited disorder called sitosterolemia, the pump that normally ejects these compounds from the gut wall is missing, so they build up in blood and tissue and drive artery disease from an early age.
Also known as
Used in a sentence
The diet history noted daily use of a spread enriched with plant sterol esters.
Good to know
Plant sterols lower measured low-density lipoprotein reliably, yet no trial has shown that eating them reduces heart attacks or strokes, and in the rare inherited disorder sitosterolemia they accumulate in the blood and cause early artery disease.
Word origin
Where “plant sterol” comes from
Sterol joins the Greek stereos, meaning solid, to the chemical ending -ol, which marks an alcohol. The plant prefix separates these compounds from the sterols animals make for themselves.