Margarine Enriched with Plant Sterols May Help Guard Against Heart Disease

What are Phytosterols?

Plant sterols, or phytosterols as they are sometimes called, are natural chemicals found in plants. They are the plant equivalent of cholesterol, and play a role in the structure of plant cell membranes. In the late 1990s, scientists discovered that they are so similar to cholesterol that they can fool the body into thinking that they are cholesterol. Phytosterols, which encompass plant sterols and stanols, are steroid compounds similar to cholesterol which occur in plants and vary only in carbon side chains and/or presence or absence of a double bond. Stanols are saturated sterols, having no double bonds in the sterol ring structure. More than 200 sterols and related compounds have been identified. Free phytosterols extracted from oils are insoluble in water, relatively insoluble in oil, and soluble in alcohols.

This is very useful, because they can masquerade as cholesterol and interfere with its uptake into the body in the digestive tract. Research at the Chicago Center for Clinical Research in 1999 showed that, consumed regularly, plant sterols can reduce concentrations of what everyone calls the ‘bad cholesterol’, LDL (low-density lipoprotein).

Phytosterols occur naturally in small amounts in vegetable oils, especially soya bean oil, which is why for a while soya was seen as a healthy food. Now many margarines, breakfast cereals and spreads are artificially enriched with plant sterols and marketed as health foods for those worried about high cholesterol levels. Such products are now big business.

In February 2005, Coca-Cola announced that it was going to launch a range of drinks fortified with plant sterols. In November 2006, scientists at UC Davis reported that twice-daily servings of a reduced-calorie orange drink with added plant sterols lowered levels of a chemical in the body called C-reactive protein. C-reactive protein is a sign of inflammation, and a well-known warning marker for heart disease. Professor Ishwarlal Jialal, the leader of the study, acknowledges that the best way to fight heart disease is through changes in diet and exercise. But, he says, people often can’t make the necessary changes. Plant sterol fortified juices may therefore be at least a help. This research was funded by Coca-Cola as well as the National Institute for Health.

Other scientists think the best way to use plant sterols is in pill form. They argue that taking them in fortified foods is unpredictable and erratic. It’s impossible to be sure, for instance, when eating out, that the food is suitably fortified. Studies at Washington University in 2006 suggested that such pills could reduce LDL, but they are not yet approved for use.

Plant Sterols Lowers Cholesterol

The ability of phytosterols to reduce cholesterol levels was first demonstrated in humans in 1953. They were subsequently marketed as a pharmaceutical under the name Cytellin as a treatment for elevated cholesterol from 1954-1982. 

Unlike the statins, where cholesterol lowering has been proven to reduce CVD risk and overall mortality under well-defined circumstances, no such effect has ever been documented with phytosterol-enriched foods or phytosterol OTC medications. While cholesterol lowering was frequently used as a surrogate endpoint for beneficial effects on CVD, counter-examples exist where specific medications for cholesterol lowering were found to have unfavorable effect on clinical endpoints, such as with ezetimibe.

Coadministration of statins with phytosterol-enriched foods increases the cholesterol-lowering effect of phytosterols, again without any proof of clinical benefit and with anecdotal evidence of dangerous adverse effects. 

Statins work by reducing cholesterol synthesis by inhibiting the rate-limiting HMG-CoA reductase enzyme. Phytosterols reduce cholesterol levels by competing with cholesterol absorption in the gut, a mechanism which complements statins. Phytosterols further reduce cholesterol levels by about 9% to 17% in statin users. The type or dose of statin does not appear to affect phytosterols’ cholesterol-lowering efficacy. 

Because of their cholesterol reducing properties, some manufacturers are using sterols or stanols as a food additive. 

How to Get Sterols and Stanols Into Your Diet?

Frechman says it's easy to add in these foods to your diet. "When you are putting a spread on your whole-grain bread or rolls, choose one with sterols or stanols.  If you use butter or margarine now, just switch over to one of these sterol-fortified spreads."

If you don't eat butter or margarine now, this is not an invitation to start slathering on the spread. More is not better. Extra margarine spread -- with or without stanols and sterols -- means extra calories.

You can also find plant sterols or stanols in some cooking oils, salad dressings, milk, yogurt, snack bars, and juices. Indeed, so many fortified products are headed to grocery store shelves that you'll soon have a dizzy array of choices. But check the labels carefully. While plant sterols are healthy, extra calories are not. Excess calories simply lead to excess pounds.

How Much Plant Sterols Do You Need?

The National Cholesterol Education Program recommends that people who have high cholesterol get 2 grams of stanols or sterols a day.



References:


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