ATLANTA, Nov. 8 -- A low-fat spread made from vegetable oil with added sterol esters could reduce the risk of heart attack and stroke for millions of people, according to a study presented today at the American Heart Association Scientific Sessions.
Sterol esters are similar to cholesterol, which is found in meat and dairy products. But sterols are derived from plant oils. The substances are structurally similar to cholesterol so they interfere with cholesterol absorption in the intestines.
The good news is that the sterol spread seems to lower LDL -- low-density lipoprotein, the so-called "bad" cholesterol -- without lowering HDL, also known as the "good" cholesterol, says lead researcher Kevin C. Maki, Ph.D., director of the Nutrition and Metabolism Research Unit at the Chicago Center for Clinical Research.
"From a public health standpoint, high cholesterol levels are a huge problem. Roughly half of the U.S. population has high cholesterol," he says. "If we can find more non-drug options that will help people lower their cholesterol levels, it would have a great impact on reducing their risk of cardiovascular disease."
There are two FDA-approved cholesterol-lowering spreads. The one used in this study, Take Control, contains vegetable oil sterol esters from soybeans. The other spread, Benecol, contains plant stanol esters, which come from wood pulp from pine trees. The stanol-based spread has been used in Finland since 1995. The spreads won U.S. Food and Drug Administration approval this year and are sold in grocery stores.
Cholesterol is a fatty substance that forms deposits in the blood vessel. Blood vessels that become severely blocked by cholesterol deposits are unable to supply blood to the heart or brain, triggering a heart attack or stroke. In a study of 224 people with cholesterol levels in the mildly to moderately high range, the spread lowered cholesterol levels at doses of 1 to 2 grams per day over a five week period, Maki says. The subjects in the study were divided into three groups. The control group followed a low-fat, low-cholesterol diet and consumed a control low-fat spread. The other two groups followed the same diet with one group eating the 1-gram dose and the other taking 2 grams of the sterol spread.
The study was a "double-blind study" in which neither the researchers nor the subjects were aware of which spread the subjects were eating. According to Maki, was that more was not necessarily better when it came to the sterol spread's cholesterol-lowering benefits. In fact, those eating 2 grams per day of the substance showed similar cholesterol-lowering rates as those eating the 1-gram amount. The drop in LDL cholesterol was 7.6 percent in the 1-gram group and 8.1 percent in those consuming 2-grams per day. The control group participants who didn't consume the soybean spread saw an average increase in LDL cholesterol of 2.7 percent.
"It surprised us that the low- and high-dose versions of the spread offered almost equal benefits. That's good news because you don't have to consume very much to get cholesterol-lowering, which might keep the cost down. However, it was disappointing because we had hoped that the more the subjects ate, the more their cholesterol levels would decrease," says Maki.
People with very high cholesterol levels will still need to follow a diet low in saturated fat and cholesterol and probably take cholesterol-lowering drugs as well, Maki says. Individuals with a total cholesterol level of 200 milligrams per deciliter (mg/dl) have a relatively low risk of heart disease. However, the risk of heart disease increased by 50 percent in those with a total cholesterol level of 240 mg/dl. Study participants had a level of 240 mg/dl when the study began.
Because sterols affect cholesterol metabolism, researchers wanted to know if they would reduce the good cholesterol that helps clear the bad cholesterol from the blood stream. The spread did not affect HDL cholesterol levels. It did, however, lower the amount of the antioxidant beta-carotene, which is fat-soluble and transported with cholesterol. Antioxidants help prevent damage from oxygen free radicals, which are unstable molecules that can damage cells. Although beta-carotene levels dropped by as much as 20 percent in some of the study participants, they remained in the normal range.
Previous studies show that simply eating a diet that is low in both saturated fat and cholesterol can reduce LDL cholesterol levels by 5-10 percent. "So, if on top of that you can get another five percent reduction with a product like this, you're talking about a 10 to 15 percent reduction in LDL cholesterol, which over time may reduce the risk of heart disease by 15 to 30 percent or more," says Maki.
"Compared to the 20 percent reductions associated with some drug therapies for high cholesterol, a five percent drop in the bad LDL looks pretty small. But in terms of public health significance, five percent translates into potentially millions of reduced heart attacks."
Co-authors include Michael H. Davidson, M.D.; Denise Umporowicz, M.S., Ernst Schaefer, M.D.; Mary R. Dicklin, Ph.D.; Kate A. Ingram, M.P.H., R.D.; Shirley Chen, Ph.D.; Brian Gebhart, Ph.D.; and William C. Franke, Ph.D.