Plant sterols are important because of their impact on our hormone health. Obviously eating margarine (which is a polyunsaturated fat, which increases triglycerides in the blood stream) with plant sterols added will not be as effective as eating a variety of plant species.
Green tea, ginsengs, thistles, maple, and many others can help in this regard. This is a great book on the subject:
http://www.innertraditions.com/isbn/978-1-59477-168-2