Plant sterols may pose one solution to combating the growing epidemic of high cholesterol in the United States, where an estimated 106.7 million adults have total blood cholesterol levels considered either high risk or borderline high risk. Present in many fruits, vegetables, nuts, seeds, cereals and vegetable oils, plant sterols are shown to reduce LDL “bad” cholesterol without affecting good cholesterol. But just eating fruits and vegetables doesn't get the job done. You would need to eat about 100 small potatoes to consume enough plant sterols to reap a cholesterol lowering benefit, notes Pam Stauffer, global marketing and communications manager, Cargill, Health and Nutrition, Wayzata, Minn. Therefore, plant sterols are being isolated and incorporated at concentrated levels into baked products, among other food applications, to appeal to cholesterol-conscious consumers and help bakers achieve FDA label claims about reducing cholesterol.

What are plant sterols?

“Plant sterols act as the cholesterol of the plant world in that they help provide structure and rigidity to cell walls. Additionally, they are very similar in molecular structure to animal cholesterol,” says Charles Barber, technical service manager, Cognis Nutrition and Health, LaGrange, Ill. When consumed, plant sterols compete with and impede the absorption of dietary and endogenous cholesterol, preventing absorption in the bloodstream, he adds.

Two types of plant sterol products exist: free sterols and sterol esters. Free sterols are a waxy material with a high melting point of 245°F (135°C ) to 293°F (145°C). Free sterols are sold in finely ground powders, which manufacturers sometimes add to a carrier before introducing them into a food application. A sterol ester is formed when a fatty acid is esterified onto the sterol molecule. Sterol esters have the consistency of petroleum jelly and a melting point of 95°F (35°C) and can be used to replace part of the fat in formulas. They usually are sold in powder or semi-liquid forms. In their pure form, sterol esters are a liquid, when refrigerated they become solid and at ambient temperature they are a yellow or white paste. Food manufacturers heat sterol esters until they form a clear oil and then incorporate that oil into baked products.

“Sterol esters are mainly used in margarine-type products,” says J.J. Mathieu, ADM Technical Services, Decatur, Ill. “In baked products, one could use either product, but bakers may choose to use the more convenient free sterols powder product.”

Benefits and role in lowering cholesterol

Plant sterols' main benefit is that they help lower cholesterol and thus reduce the risk of heart disease. According to the FDA, “Foods containing at least 0.4 g per serving of plant sterols (0.65 g sterol esters), eaten twice a day with meals for a daily total intake of at least 0.8 g (1.3 g sterol esters), as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”

Plant sterols have a 94 percent purity, while sterol esters have a 60 percent sterol content, notes Carol Lowry, senior applications scientist, Cargill, Heath and Nutrition. The daily intakes noted above are based on these differences in purity.

Studies continue to show the cholesterol lowering benefits of plant sterols. A Mayo Clinic meta-analysis, for example, showed that 2 g per day of plant sterols have been shown to lower LDL by 10 percent.

Plant sterols also benefit consumers because they are natural and, because they are being incorporated into everyday foods, such as breads and juice, they are easy for consumers to access on a daily basis. The key to reaching consumers is adding plant sterols to products they already buy, Stauffer says. This way, consumers don't have to make major adjustments to their diet to incorporate plant sterols.

“Sterol-containing baked products can also be complementary to other ingredients that are known to reduce cholesterol, such as soluble fibers and soy protein,” Mathieu adds.