In both animals and plants, sterols and stanols are essential components of the cell membrane. Phytosterols are present in all foods of plant origin. The human diet includes about mg of. Phytosterols, because of their similar structure to cholesterol, compete with cholesterol absorption mechanisms in the intestine. The amounts of phytosterols present in the diet, however, are not usually sufficient to affect blood levels of.
Dietary intakes of phytosterols of mg per day or higher are needed to cause a measureable reduction in blood LDL cholesterol absorption Hendriks et al The structures of 4 major phytosterols found in plant sources are compared to that of cholesterol in Figure 1.
Phytosterols are divided into two main types: Sterols and stanols. In the sterol form, the bond is unsaturated shown as a double line. In the stanol form, the bond is saturated shown as a single line. Figure 1: Molecular structure of cholesterol compared to sterols, stanols and a fatty acid ester Also shown is a fatty acid ester of sitostanol. In this example, oleic acid is linked to the 3 position on the sterol ring replacing the hydroxyl group. Fatty acids can form ester linkages on all of the phytosterols at this position.
Fatty acid esters are created by linking free sterols and stanols to free fatty acids in the presence of a food grade catalyst. When ingested, fatty acid esters are split by digestive enzymes in the intestine to release the active free sterols and stanols.
Fatty acid esters of phytosterols were developed to increase the solubility of phytosterols in vegetable oils. The primary use of esters is in manufacturing margarines. The non-esterified phytosterol forms are better for water based food products such as yogurts and juices.
Corn oil, for example, contains only. Because they are found only in small amounts naturally, for years, plant sterols and stanols were thought to be an unattainable nutrient source. This changed in the s, when scientists found a way to extract plant sterols and stanols from plants and add them to food so that the cholesterol fighting properties of these nutrients could finally be put to use.
Today, foods fortified with plant sterols and stanols include orange juice, breads, cheese, milk, and butter products. Consuming two grams of plant sterols a day can help reduce cholesterol by around 10 percent and could lead to a 20 percent lower chance of heart disease.
Because these foods are not low in calories, those interested in increasing their plant sterol and stanol consumption must be mindful when eating fortified foods to guard against weight gain. For those who do not want to make diet changes, supplements offer an alternative means of plant sterol and stanol consumption.
For best absorption, do not consume the entire daily recommended serving of plant sterols and stanols in one sitting, but rather in smaller amounts throughout the day. 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.
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