Phytosterols, also known as plant sterols, are a group of naturally occurring steroid alcohols found in the cell membranes of plants. Their chemical structure is similar to that of cholesterol, differing primarily in the side chain at the C-24 position. Common examples include β-sitosterol, campesterol, and stigmasterol. The primary and most significant application of phytosterols is as a functional food ingredient for cholesterol management. They are added to various food products such as margarines, spreads, dairy products, and dietary supplements. Their mechanism of action involves competitively inhibiting the intestinal absorption of dietary and biliary cholesterol, thereby helping to lower total and LDL ("bad") cholesterol levels in the blood. This health benefit is well-established and supported by regulatory authorities like the FDA and EFSA, which approve specific health claims for phytosterol-enriched foods. Beyond their use in functional foods, phytosterols also find applications in the pharmaceutical and cosmetic industries. In pharmaceuticals, they can serve as starting materials for the synthesis of steroid hormones and as excipients. In cosmetics, they are valued for their skin-conditioning and emulsifying properties. They are generally recognized as safe (GRAS) for consumption at recommended levels.