Phytosterols which include plant sterols and stanols, are steroid compounds. These are similar to cholesterol which occurs in plants except variation only in carbon side chains and/or presence or absence of a double bond. Stanols are saturated sterols, whose sterol ring structure has no double bonds. Over 200 sterols and related compounds have been identified till date. Free phytosterols extracted from oils are insoluble in water, comparatively insoluble in oil, and soluble in alcohols.
In 1953 it was first demonstrated in humans that phytosterols have got the ability to reduce cholesterol levels. They were later on marketed as a pharmaceutical under the name Cytellin as a treatment for elevated cholesterol from 1954-1982.
A potential safety concern relating to phytosterol consumption is in patients with phytosterolaemia, a rare genetic disorder which results in a 50- to 100-fold increase in blood plant sterol levels and is associated with rapid development of coronary atherosclerosis.
Unlike the statins, where cholesterol lowering has been proven to reduce CVD risk and overall mortality under well-defined circumstances, no such effect has ever been documented with phytosterol-enriched foods or phytosterol OTC medications. While cholesterol lowering was frequently used as a surrogate endpoint for beneficial effects on CVD, counter-examples exist where specific medications for cholesterol lowering were found to have unfavorable effect on clinical endpoints, such as with ezetimibe.