Plant sterols cholesterol-lowering properties

Plant sterols such as sitosterol and camposterol, as by-products from vegetable oils at prices of about 15 kg-1, are also important starting materials for the production of steroid hormones. A new application is the cholesterol lowering property of these sterols esterified with fatty acids (with a production of about 10000 t a 1). They can be found in the margarine Becel pro-active of Unilever. A Finnish equivalent is Benecol, which contains stands such as sitostanol and campostanol, sterols having the 5,6-double bound hydrogenated, also esterified with fatty adds [33]. 

The cholesterol-lowering properties of dietary plant sterols have been known for decades (Best et al., 1954 Peterson, 1951 Poliak, 1953), due specifically to reductions in cholesterol absorption. Inverse correlations between plant sterol intake and cholesterol absorption have been reported in animals (Carr et al., 2002 Ntanios and Jones, 1999) and humans (Ellegard et al., 2000). The exact mechanism by which plant sterols inhibit cholesterol absorption is unclear, and several mechanisms of action have been proposed, including (1) competition with cholesterol for solubilization in micelles within the intestinal lumen, (2) cocrystallization with cholesterol to form insoluble crystals, (3) interaction with digestive enzymes, and (4) regulation of intestinal transporters of cholesterol. 

The cholesterol-lowering properties of phytosterols were first demonstrated in the early 1950s by Peterson (1951), who fed cholesterol and plant sterols to chicks and found that soy sterols inhibited the increase in cholesterol concentration otherwise induced by cholesterol feeding. Shortly afterwards, Poliak (1953) showed the same effect in humans, to whom he administered 5-10 g of crude sitosterol daily for up to 8 months. In similar studies in rabbits, he observed that sitosterol was poorly absorbed and that, if present in excess, it blocked the absorption of cholesterol and prevented atherosclerosis. Poor absorption and lack of any endogenous synthesis of sitosterol in humans were subsequently demonstrated by Salen et al. (1970). 

Phytosterols (PS) are plant sterols and stanols widely distributed in plant sources that resemble cholesterol in terms of structure and physiological functions. The cholesterol-lowering capacity of PS is well documented in animal and human studies. However, recent studies suggest that the beneficial effects of PS are not only limited to their hypocholesterolemic capacity as they can also act as immunomodulatory, anti-inflammatory, and antidiabetic agents. Further, there is a growing body of evidence which supports that they play an important role in the prevention of other diseases such as cancer and atherosclerosis. Nevertheless, the mechanisms by which PS exert their beneficial functions, the physiological relevance of PS, and their potential adverse effects are not yet fully understood. Therefore, the main aim of this chapter is to provide a contemporaneous overview of the beneficial properties of PS, their mechanism of action, and safety. 

Othman RA, Moghadasian MH (2011) Beyond cholesterol-lowering effects of plant sterols clinical and experimental evidence of anti-inflammatory properties. Nutr Rev 69(7) 371-382.doi 10.1111/j.l753-4887.2011.00399.x... 

Irrespective of the actual mechanisms behind the reduction of cholesterol absorption by plant sterols, solubilization into the emulsified fat phase of the food digest is a prerequisite for plant sterols to be incorporated into the micelles. The physical properties of free, crystalline plant sterols and stanols limit their applicability in foods and their cholesterol-lowering effect in many food matrices, but these limitations can be partly solved by producing fat dispersions of plant sterols or emulsifier-sterol aggregates. Currently, however, plant sterols are mainly used as fatty acid esters in functional foods. 

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