DALLAS -- One out of three women in a study were able to normalize their blood cholesterol levels by replacing regular canola margarine with one that contains a cholesterol-blocker called sitostanol ester, according to today's American Heart Association journal Circulation.
Sitostanol ester, a biochemical cousin of cholesterol, engages in tug-of-war in the intestine with blood cholesterol to thwart absorption of cholesterol and keep it from being deposited in blood vessel walls. Cholesterol deposits cause the blood vessel blockages that lead to heart attacks and strokes.
Sitostanol appears doubly effective for those who also are taking cholesterol-lowering drugs, and it may allow individuals to reduce dosage of such drugs, says Tatu Miettinen, M.D., professor of internal medicine of the University of Helsinki, Finland.
"The present findings showed for the first time that sitostanol ester margarine effectively inhibited cholesterol absorption. The results suggest that a third of women with heart disease can be treated using only dietary sitostanol ester margarine and not cholesterol-lowering drugs," he says.
Sitostanol margarine is sold in Finland, but it is not available in the United States, although there is some commercial interest in marketing it in this country.
"The sitostanol is totally tasteless and people cannot tell the difference between margarine with and without sitostanol, and one can cook with it as with regular margarine," says Miettinen.
The study included two groups of postmenopausal women with diagnosed heart disease. One group of 22 women ate low-fat "home diets" followed by a similar seven-week diet that contained three grams per day of margarine with sitostanol ester. For the next seven weeks they ate the same amount of margarine without the sitostanol ester. A second group of 10 women who were taking the cholesterol-lowering drug simvastatin ate sitostanol margarine for 12 weeks.
While the canola oil margarine reduced cholesterol levels overall by about 5 percent, the sitostanol ester-enriched spread was much more effective. The sitostanol ester margarine lowered total blood cholesterol levels by an average of 13 percent and LDL, or low-density lipoprotein, the "bad" cholesterol, by 20 percent. Combining the sitostanol margarine with drug therapy further reduced total and LDL cholesterol levels by 11 percent and 16 percent respectively, the study shows.
Individuals taking the sitostanol ester and the drug combination were able to reduce medication dose and sometimes eliminate the need for the drug more often than individuals who were only taking the drug. Sitostanol reduced cholesterol in all of the 32 women tested and trimmed amounts of LDL to below 100 milligrams per deciliter of blood, considered a healthy level. By contrast, none of the women's LDL levels went down to this desirable level while they were on a regular low-fat "home diet", the researchers say.
Slowing the body's production of cholesterol and reducing its absorption into the body can lower blood levels of cholesterol. Drugs of the so-called statin family, which have recently been shown to dramatically slash the risk of dying from heart attacks, reduce the amount of cholesterol by blocking a key enzyme that body cells need to manufacture cholesterol. Sitostanol ester works via the other route, blocking cholesterol absorption.
One problem, however, is that when the body senses that less cholesterol is being absorbed, it responds by making more, potentially reducing the effectiveness of absorption-blocking efforts. Researchers found that while sitostanol ester sharply inhibited cholesterol absorption, it also stimulated extra production. Thus, the Helsinki research team says that using combined therapies that work on both pathways at the same time may prove most beneficial, "especially for the patients not responding satisfactorily to sitostanol ester margarine alone."
Some individuals naturally tend to produce more cholesterol while others absorb it more efficiently, the scientists explain. Sitostanol ester margarine appears to be most effective in those people who have higher cholesterol absorption rates and correspondingly lower cholesterol production, while statin drug therapy is most beneficial for those with high production rates who don't respond to sitostanol ester in the diet.
Other dietary studies of dietary sitostanol ester have suggested that cholesterol-lowering benefits in men are similar to those found in the new study of postmenopausal women, the researchers add.
Co-authors are Helena Gylling, M.D., and Rajaratnam Radhakrishnan, M.D., of the University of Helsinki, Finland.
Circulation is one of five scientific journals published by the American Heart Association, which has its national headquarters in Dallas.
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Media advisory: Dr. Miettinen can be reached in Helsinki by calling 358-9-471-2220, or by fax 358-9-471-4013. Reporters may call (214) 706-1173 for copies of his report. (Please do not publish telephone numbers.)