sitosterol

Sitosterol, commonly referred to as beta-sitosterol, is a plant sterol (phytosterol) that is structurally similar to cholesterol. It is one of the most abundant phytosterols in the human diet, occurring in many plant-containing foods such as vegetable oils, nuts, seeds, fruits, and whole grains. Its chemical formula is C29H50O and its molecular weight is about 414.7 g/mol.

Sitosterol occurs naturally in plants and can be consumed as part of a regular diet. In the body, it is thought to interfere with cholesterol absorption by competing for incorporation into intestinal micelles, which can modestly lower serum low-density lipoprotein (LDL) cholesterol when consumed at levels used in fortified foods or supplements. Beyond cholesterol effects, sitosterol (beta-sitosterol) is marketed as a supplement for urinary symptoms associated with benign prostatic hyperplasia, with evidence showing potential benefits that vary by study.

Regulatory and dietary use: Plant sterol esters and free sitosterol are approved in many regions for addition to foods and supplements designed to reduce cholesterol absorption. Effective intakes are typically around 1.5 to 3 grams per day, consumed as part of a balanced diet; such use is not a substitute for medical therapy when it is indicated.

Safety and precautions: Sitosterol is generally safe at typical dietary levels. High-dose intake may cause gastrointestinal symptoms and can influence the absorption of fat-soluble vitamins. Individuals with sitosterolemia, a rare genetic condition, accumulate plant sterols and should avoid plant sterol supplements. People on medications affecting fat-soluble vitamin absorption should consult a clinician.

Related compounds include campesterol and stigmasterol.