Ask a Dietitian

What is a plant sterol?
Plant sterols are a structural component of the plant membrane found in small amounts in a variety of plant foods such as nuts and seeds, whole grains, vegetable oils, vegetables such as broccoli, tomatoes and carrots and fruit such as oranges and apples. They have a similar structure to cholesterol in humans.

How Plant Sterols work
In our intestines, plant sterols can help block the absorption of cholesterol from the gut by displacing cholesterol from the micelles. In this way, less cholesterol is presented to the lining of the intestinal wall in a form that can be absorbed.
The latest meta-analysis (Katan etal Mayo Clinics Proc 2003) concluded that 2 grams of plant sterols daily provide, on average, a 10% reduction in cholesterol when consumed at least twice a day with meals. Over 140 clinical studies have shown that plant sterols can significantly lower total and LDL cholesterol. Moreover, plant sterols have little or no effect on HDL when DLD is reduces, improving the total cholesterol to HDL ratio.

How can you get it?
In order to consume enough plant sterols through foods you would have to eat 11 cups of peanuts or 425 tomatoes to get 2g of plant sterols. Food manufacturers have recognized this valuable functional ingredient and have begun adding it to foods such as spreads, milk drinks, yogurt and yogurt drinks. Unfortunately they are only available in countries such as the US, Australia, the European Union, Israel and Japan, not in Canada. Health Canada is currently reviewing claims for sterol enriched products in Canada. Many Health Authorities such as the International Atherosclerosis Society, British Heart Foundation, Heart Foundation of Australia and the American Heart Association, among others, have developed guidelines for the prevention of CHD and have included a recommendation of 2g plant sterol/stanol per day.

Average Daily Intakes
Average intakes of plant sterols have decreased over the years and today they range from 0.15 grams-0.31grams. In vegetarian diets average intake are closer to 0.6 grams.
2 Tbsp plant sterol enriched spread = 2 g plant sterols
11 cups of peanuts = 2g plant sterols
425 tomatoes = 2 g plant sterols

Safety
In clinical trials no adverse effects were seen and in safety tests of up to 30 times safety factor showed no toxicity and no effect on bile acids, gut flora, serum levels of female sex hormones, clinical chemistry, hematology or urinary analysis. However, consuming plant sterol enriched foods may reduce the absorption of fat soluble vitamins, and has been shown to reduce blood levels of carotenoids, including beta carotene and lycopene. This reduction can be prevented by ensuring an intake of more than 5 servings of vegetables and fruit and including at least one or more caroteinoid-rich sources such as carrots, tomatoes or squash. Plant sterols are not recommended for women who are pregnant or breastfeeding, children and people with sitosterolemia.

Functional foods that may help lower cholesterol (as per the Portfolio Diet by Dr. David Jenkins of the University of Toronto:

Plant sterol enriched foods (1g/1000kcal)
Viscous fibres in oats, psyllium, barley, okra and eggplant (10g/1000kcal)
Soy protein (21.4g/1000kcal)
Nuts such as almonds (14g/1000kcal)

The Bottom Line:
Including 2 g of plant sterols daily to help lower cholesterol may help reduce CHD risk. Most benefit would be achieved by adding plant sterols in addition to a healthy diet low in saturated and trans fats, high in fibre, fruit and vegetables. A reduction in cholesterol can be seen in 3 weeks and can be sustained with continued consumption of the plant sterols.

Source: Heart Headlines; Fall 2007, Volume 13, Issue 3
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