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New cholesterol-lowering margarines: Are they better?

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Two new cholesterol-lowering margarines have been approved by the U.S. Food and Drug Administration as "foods." Benecol (McNeil Consumer Health Care) contains hydrogenated sterols, primarily sitostanol derived from pine tree wood pulp. The other product is Take Control (Unilever), which contains naturally occurring unsaturated sterols, primarily sitosterol from soybean oil. The chemical structure of plant sterols resembles cholesterol. The stanol esters in Benecol are produced from sterols by hydrogenation and esterification with unsaturated fatty acids. Consultants for the Medical Letter on Drugs and Therapeutics reviewed the efficacy of these sterol-rich margarines in reducing low-density lipoprotein (LDL) cholesterol levels.

When plant sterols are administered orally, intestinal absorption of dietary and biliary cholesterol is decreased, and fecal excretion is increased. It appears that the poorly absorbed sterols compete with cholesterol for incorporation into mixed bile salt micelles, a prerequisite for uptake of cholesterol by enterocytes. The decreased supply of intestinal cholesterol available to the liver results in decreased production and increased excretion of LDL cholesterol precursors, thus decreasing LDL production. It is postulated that some patients do not respond to sterols because of the liver's attempt to increase cholesterol synthesis in response to decreased availability of cholesterol.

A double-blind, randomized trial compared plant sterol esters and sitostanol ester in margarine with a control margarine in normal and mildly hypercholesterolemic patients. After 3.5 weeks, the two enriched margarines had lowered LDL cholesterol levels by about 12 percent compared with the control margarine. Another crossover study with similar comparisons demonstrated a 6.7 to 9.9 percent reduction of LDL cholesterol levels when a sterol mixture containing 48 percent sitosterol in a full-fat (70 percent) margarine was used and compared with a control margarine.

Another double-blind trial in mildly hypercholesterolemic persons randomized participants to use margarine without sitostanol or the same margarine containing 3 g of...