Throughout much of human evolution, it is likely that large amounts of plant foods were consumed (1). In addition to being rich in fiber and plant protein, the diets of our ancestors were also rich in phytosterols—plant-derived sterols that are similar in structure and function to cholesterol. There is increasing evidence that the reintroduction of plant foods providing phytosterols into the modern diet can improve serum lipid (cholesterol) profiles and reduce the risk of cardiovascular disease (2).
Although cholesterol is the predominant sterol in animals, including humans, a variety of phytosterols are found in plants (3). Nutritionists recognize two classes of phytosterols: sterols, which have a double bond in the sterol ring (Figure 1), and stanols, which lack a double bond in the sterol ring (Figure 2).The most abundant sterols in plants and the human diet are sitosterol and campesterol. Stanols are also present in plants, but they comprise only about 10% of total dietary phytosterols. Cholesterol in human blood and tissues is derived from the diet as well as endogenous cholesterol synthesis. In contrast, all phytosterols in human blood and tissues are derived from the diet because humans cannot synthesize phytosterols (4).
* Phytosterols are plant-derived compounds that are similar in structure and function to cholesterol.
* Although early human diets were rich in phyotosterols, providing as much as 1 g/d, the typical Western diet today is relatively low in phytosterols.
* Phytosterols inhibit the intestinal absorption of cholesterol.
* Numerous clinical trials have demonstrated that daily consumption of foods enriched with at least 0.8 g of plant sterols or stanols lowers serum LDL cholesterol.
* Although some epidemiological studies have found that higher intakes of plant foods containing phytosterols are associated with decreased cancer risk, it is not clear whether phytosterols or other compounds in plant foods are the protective factors.
* The results of a few clinical trials suggest that phytosterol supplementation at relatively low doses can improve urinary tract symptoms related to benign prostatic hyperplasia, but further research is needed to confirm these findings.
* Foods rich in phytosterols include unrefined vegetable oils, whole grains, nuts and legumes.
* Foods and beverages with added plant sterols or stanols are now available in many countries throughout the world.
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