Phytosterols are plant sterols, mainly campesterol and sitosterol, and their respective stanols (5α-saturated derivatives), which chemically resemble cholesterol. They are present in a normal diet and are absorbed proportionally to cholesterol, but to a much lesser extent, such that less than 0.1% of serum sterols are plant sterols. Phytosterols inhibit intestinal cholesterol absorption, and fat-soluble plant stanol esters were introduced as a functional food for lowering serum cholesterol in the early 1990s; plant sterol esters entered the market at the end of the 1990s. Inhibition of the intestinal absorption of cholesterol stimulates cholesterol synthesis, a factor which limits serum cholesterol lowering to about 10% with phytosterols. Enrichment of the diet with plant stanol esters reduces absorption and serum concentrations of both cholesterol and plant sterols, whereas enrichment of the diet with plant sterol esters, especially in combination with statins, lowers serum cholesterol but increases serum plant sterol levels. Recent studies have suggested that high-serum plant sterol levels may be associated with increased coincidence of coronary heart disease. Estimates of coronary heart disease reduction by 20-25% with plant sterols/stanols is based mainly on short-term studies. Long-term cholesterol lowering, needed for the prevention of coronary heart disease, may be successful with plant stanol esters, which lower serum cholesterol in both genders over at least a year.
Cholesterol lowering effects of milk with added plant sterols
