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Eating mayo to lower your cholesterol? Not so fast

Move over, oat bran. Coming to a store near you is the latest touted weapon against high blood cholesterol.

Last month, Health Canada gave food companies the green light to fortify certain foods with plant sterols – also called phytosterols – to help Canadians consume sufficiently high levels to lower cholesterol. Already, Unilever has taken advantage of the new regulation with the launch of its Becel pro.activ margarine. That's just the beginning. Expect to see spreads, mayonnaise, salad dressings, yogurt and juices boasting the addition of plant sterols on the market soon.

The arrival of plant-sterol-fortified foods is good news for the 50 per cent of Canadian adults considered to have elevated LDL cholesterol. But they're not a magic bullet.

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Plant sterols have a similar chemical structure to food cholesterol. But rather than boosting blood cholesterol, their molecular resemblance enables them to compete with dietary cholesterol in the intestine for absorption into the bloodstream. Plant sterols have been shown to reduce the absorption of dietary cholesterol by about 50 per cent. With less cholesterol available to make hormones, bile acids and vitamin D, the body is forced to pull cholesterol from the blood for these important functions.

Studies have consistently found that consuming plant sterols in sufficient amounts can lower LDL cholesterol by up to 15 per cent after three weeks when combined with a healthy diet.

A typical diet provides about 0.2 milligrams of plant sterols, a far cry from the amount needed to cut cholesterol levels. Based on the available evidence, an intake of 2 to 3 grams a day is needed to lower LDL cholesterol. Five teaspoons (25 millilitres) of Becel pro.activ margarine delivers 2 grams of plant sterols. Children with elevated blood cholesterol can safely consume 1 gram of plant sterols daily.

You won't find the grams of plant sterols on the nutrition facts box of fortified foods. However, foods that meet Health Canada's criteria can now carry the statement: "One serving provides x% of the daily amount [2 grams] of plant sterols, shown to help reduce cholesterol in adults."

In addition, an eligible food may also boast a health claim on its package, including: "Plant sterols help reduce cholesterol" and: "High cholesterol is a risk factor for heart disease."

The cholesterol-lowering effect of plant sterols varies widely among individuals. Studies have found that people with high to very high blood cholesterol experience a much greater effect than those with borderline high cholesterol.

Timing also seems to matter. For optimal cholesterol lowering, it's best to consume plant sterol fortified foods in smaller amounts two or three times a day rather than only once.

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It's still important to follow a heart-healthy diet and include other foods that lower cholesterol, though. In fact, doing so can help you get a larger drop in LDL cholesterol.

David Jenkins, Canadian Research Chair in Metabolism and Nutrition at the University of Toronto and St. Michael's Hospital, says a "portfolio" diet that adds daily soy protein, almonds, soluble fibre and plant sterols (2 grams a day) to a diet that's low in saturated fat and cholesterol has been shown to lower LDL cholesterol by as much as 29 per cent.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday.

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