A plant stanol is a small, but essential, chemical compound that acts as a component of the cellular membranes of certain plants. Stanols belong to a class of naturally occurring plant compounds termed phytosterols. Researchers recognize two forms of phytosterols in plants: sterols and stanols. Both are necessary structural components in plants. These substances act to protect the integrity of the cell membrane just as cholesterol does for the cells of the human body.
Scientists have been studying plant sterols and plant stanols for more than 50 years. The health benefits of both forms of phytosterols have been well established. Research studies have determined that these plant compounds have cholesterol-lowering properties. Phytosterols protect the heart by lowering low-density lipoprotein (LDL) cholesterol levels. High LDL levels are considered to be a potential precursor to the development of medical problems, such as cardiovascular disease.
Stanols work to counter high cholesterol in a manner similar to some prescription medications. A plant stanol will actually block the absorption of cholesterol in the intestine. Stanols chemically resemble the cholesterol found in animal products. Once in the bloodstream, a plant stanol simply gets in the way of dietary cholesterol. The cholesterol that cannot be completely absorbed passes out of the body as waste.
A plant stanol is a naturally occurring substance. It cannot be manufactured by the body as cholesterol can. Instead, it must be consumed. Only wood pulp, certain types of grains, vegetables, fruits, nuts, legumes, and vegetable oils contain plant stanols.
Less common than sterols, plant stanols comprise only about 10 percent of the total phytosterols in plants. Sterols account for the remaining 90 percent. Due to their low concentration, it is very difficult to consume enough plant stanols from natural food to effectively lower cholesterol. In the 1980s, scientists developed a method to extract both stanols and sterols from plants. The compounds formed by the extraction process are called plant stanol esters.
Following the esterification process, stanols are more fat-soluble and, consequently, can be easily added to foods that contain fats. A variety of functional foods such as margarines, salad dressings, and cheese, have now been created that make it possible to incorporate a high enough concentration of plant stanols into the diet to help in lowering cholesterol. According to the United States Food and Drug Administration (USDA), the daily consumption of 3.4 grams of plant stanol esters, along with a low-fat diet, may have a cholesterol-lowering effect.