Sterols are a form of cholesterol found in plants and animals. In plants, sterols act as fatty tissue, contributing to cellular growth, propagation and structural support. The sterols found in plants when ingested by humans blocks excess cholesterol from entering into the bloodstream, thus aiding in the reduction of cholesterol levels. Three types of plant sterols have proven significant in cholesterol and health management.
Sterols, also referred to as phytosterols, are found in fruits, vegetables, whole grains and seeds. Sitosterol is prevalent in wheat germ, flax and pumpkin seeds, soybeans and peanuts. A specific sitosterol, beta-sitosterol, is incorporated into commercial foods such as margarine and corn oil. While such products may be marketed as heart healthy because of the sterols' cholesterol-lowering properties, those with low HDL (good cholesterol) levels should limit the amount of additive beta-sterols in their diet.
Many foods have been fortified with the sterol stigmasterol, including shortening and margarines, baking chocolate, salad dressings and corn chips. Stigmasterol is found naturally in corn, nuts, eggs, avocados, grape leaves, lemon grass and most fruits and vegetables. Soybeans are also rich in stigmasterol, and it contains antioxidants that may aid in reducing the risk of prostate cancer.
Campesterol is found in the herb yarrow in significant quantities. In conjunction with other compounds, the phytosterol in yarrow acts as an anti-inflammatory agent, promotes healthy liver function and aids in the reduction of cholesterol levels.
Sterols are monounsaturated fats. Stanols are fully saturated fats and are derived from phytosterols, in particular sitosterol. Like phytosterols, stanols are structurally similar to cholesterol and may contribute to controlling moderately higher cholesterol levels in humans. Stanols are incorporated into foods, often those containing fats such as margarine. Products such as fish oil capsules and other oil-based supplements contain stanols. These compounds work in conjunction with sterols to create a kind of blockade within the human body, directing monounsaturated, polyunsaturated and saturated fats away from the vascular system. The body extracts just the amount of fats it requires and the remainder is directed to the digestive system for disposal.
Though numerous foods are now fortified with plant sterols and stanols, adults with normal cholesterol levels, pregnant women and children should limit the amount of sterol-fortified foods they ingest. Higher levels of phytosterols and stanols may result in lowered levels of good cholesterol and a reduction of fats necessary for healthy body functions.