Sitosterol (a plant sterol) has been shown to lower serum cholesterol levels. The cholesterol-lowering effect is achieved by the inhibition of cholesterol absorption in the intestine. In comparisons of studies done in Europe (Finland) and the United States, response to plant sterols has been variable. It has been suggested that the difference (which show a generally more favorable effect in the Finnish studies) is the result of a higher fat and cholesterol intake in the Finnish diet. Nguyen and associates performed a randomized controlled trial of three different stanol ester margarine-like spreads compared with placebo in a U.S. population of mildly hypercholesterolemic men and women.

Eligible patients had to be older than 20 years of age, with a fasting total cholesterol level between 200 and 280 mg per dL (5.20 and 7.25 mmol per L) and a triglyceride level of 350 mg per dL (9.05 mmol per L) or lower. Patients had no clinically manifested cardiovascular disease and could not be taking a cholesterol-lowering medication. Patients were instructed to substitute 24 g of their daily dietary fat intake with three servings (8 g per serving) a day of a placebo margarine spread. At the end of four weeks, participants were randomized to receive one of three stanol ester spreads or placebo. Patients were advised to maintain their usual dietary and exercise habits. Blood samples were collected regularly during the study and six weeks after the patients had discontinued use of the study spread (week 14).

Total cholesterol values were found to be significantly reduced in all three active-ingredient groups compared with the placebo group at all points during the study. There was a dosage-dependent response in cholesterol-lowering effect. In the group taking 1 g of stanol ester three times a day, total cholesterol was lowered by 6.4 percent, and low-density lipoprotein cholesterol was lowered by 10.1 percent. There was no effect on serum triglycerides or high-density lipoprotein levels. After discontinuation of the stanol ester spreads, cholesterol levels in these patients returned to pretreatment levels.

The authors conclude that stanol esters are effective in lowering serum cholesterol levels in patients with mild hypercholesterolemia, without significant adverse side effects. Stanol esters may represent a useful adjunct in the treatment of mild hypercholesterolemia.