Functional Foods Fact Sheet: Plant Stanols and Sterols

Background
Plant sterols are present naturally in small quantities in many fruits, vegetables, nuts, seeds, cereals, legumes, vegetable oils, and other plant sources. Plant stanols occur in even smaller quantities in many of the same sources. Both stanols and sterols are essential components of plant cell membranes and structurally resemble cholesterol.

Cholesterol, as the name suggests, is itself a sterol; however, it is predominately an animal sterol. In humans, the liver synthesizes cholesterol, but an appreciable amount may also be consumed through the diet. Its presence in the body is essential for life, since it is a building block for steroid hormones, such as testosterone and estrogen, and for cell walls.

It has been well established that blood cholesterol, particularly low-density lipoprotein (LDL) cholesterol, should be controlled in the body in order to minimize the risk of coronary heart disease.(1) Excess LDL cholesterol can be oxidized to ultimately form plaque that can build up on artery walls, thereby restricting blood flow and elevating blood pressure. This is just one way that coronary heart disease develops in those at risk, and if left untreated, could lead to a heart attack or a stroke.(2)

People with high blood cholesterol levels are typically advised by health professionals to exercise and consume a diet high in fiber and low in saturated fats and cholesterol. Although these measures can reduce blood cholesterol, sometimes they don't go far enough. Other cholesterol-lowering interventions may be needed, including cholesterol-lowering medicines or adding plant sterol/stanol esters to the diet.

Health Effects

The cholesterol-lowering potential of dietary plant stanols and sterols has been known for over 50 years.(3) Although people consume plant stanols and sterols every day in food, the amounts are often not great enough to have significant blood cholesterol-lowering effects.

The challenge of incorporating larger amounts of plant stanols and sterols into the diet has been overcome recently. By modifying plant stanols and sterols structurally to form stanol and sterol esters, they are easily incorporated into fat-containing foods without losing their effectiveness in lowering cholesterol. Newer products in which stanols and sterols have been modified to form esters have shown consistent LDL cholesterol-lowering effects.(4) In the ester form and in appropriate quantities, dietary plant stanols and sterols inhibit the absorption of cholesterol in the small intestine by up to 50%, which in turn can lower LDL blood cholesterol by up to 14%.(4, 5) Patients on statin drug therapy may achieve further decreases in their blood cholesterol levels when using plant sterol and stanol esters, since statins work to decrease blood cholesterol by a different mechanism.(6)

Research

Stanols and sterols have been well tolerated in numerous clinical trials on over 1800 people, with doses up to 25 g per day. Studies have established that at least 1 gram of stanol and sterol in ester form can result in a statistically significant reduction in cholesterol.(5, 7) Recent studies of plant sterol and stanol esters in humans have shown, however, that maximum cholesterol-lowering benefits are achieved at doses of 2-3 g per day.(7-13) Intakes greater than this amount do not seem to yield any additional cholesterol reductions and, thus, higher intakes are not needed for maximum effect. As a result, the FDA authorized the use of a health claim for plant sterol and stanol esters in reducing the risk of coronary heart disease, when consumed as part of a diet low in saturated fat and cholesterol.(14) The FDA states, "Foods that may qualify for the health claim based on plant sterol ester content include spreads and salad dressings. Among the foods that may qualify for claims based on plant stanol ester content are spreads, salad dressings, snack bars, and dietary supplements in softgel form. Foods that carry the claim must also meet the requirements for low saturated fat and low cholesterol, and must also contain no more than 13 grams of total fat per serving and per 50 grams."(15)

As part of the rulemaking process for a heart health claim, the FDA requested comments on the efficacy of unesterified (free) sterols and stanols in light of recent research which has shown that free stanols and sterols in proper formulation may also lower LDL cholesterol.(16-18) The FDA recently posted a letter on the Center for Food Science and Applied Nutrition (CFSAN) Web site stating that it would consider expanding the use of the interim final health claim regarding plant stanol/sterol esters and coronary heart disease risk reduction. The action specifically cites use of free stanols and sterols as well as stanol and sterol esters and a wider range of foods including dietary supplements.(19) The FDA letter also states that the agency intends to promptly issue guidance on the issue and publish a final rule as expeditiously as possible.

Plant sterols and stanols and their esters are Generally Recognized As Safe (GRAS) food-grade substances, as a history of safe intake has not demonstrated any harmful health effects. There have been concerns that they may reduce absorption of fat-soluble vitamins such as vitamins A, E, and D. There are no reports of impaired vitamin A status or related adverse effects after several years of use in Europe and the U.S. Some studies have reported that absorption of ß-carotene was affected in some people; however, at no time did its concentration fall outside the normal range for blood levels.(7, 20, 21) Regardless, this slight reduction in ß-carotene can be compensated for by including a carotenoid rich fruit and/or vegetable in the daily diet.(22) Until there is sufficient long-term data on vitamin effects, the American Heart Association recommends limiting intake of plant stanol/sterol esters to adults with diagnosed high cholesterol.(23)

The Bottom Line

Foods supplemented with plant sterols/stanols may reduce cholesterol and are a promising addition to interventions aimed at lowering heart disease risk. The FDA has approved the following health claim for plant stanol/sterol esters and reduced risk of heart disease: Diets low in saturated fat and cholesterol that include at least 1.3 grams of plant sterol esters or 3.4 grams of plant stanol esters, consumed in 2 meals with other foods, may reduce the risk of heart disease. In addition to and in the presence of the health claim, products with plant stanol/sterol esters may also state that they can reduce cholesterol levels. Recently, the FDA indicated they will consider expanding the use of the health claim for a broader range of eligible food products comprised of free (unesterified) stanols and sterols.

Stanols and Sterols : Naturally occurring in plant materials in small quantities

Found Naturally In : Fruits, Vegetables, Nuts, Seeds, Cereals, Legumes, Vegetable Oils (particularly Soybean Oil)

Also Available In Higher Quantities In : Commercially prepared table spreads and plant stanol ester dietary supplements

Properties: (When at least 1 gram per day is consumed in ester form for statistically significant effects)

- Reduce total cholesterol
- Reduce LDL cholesterol
- Do not affect HDL cholesterol or triglycerides

References:

1) Law MR et al, BMJ 1994; 308: 367-373.
2) Ross R, Nature 1993; 362: 801-809.
3) Pollack OJ, Circ 1953; 2: 696-701.
4) Cater NB and Grundy SM, Postgraduate Medicine Special Report November 1998; 6-14.
5) Cater N, Preventive Cardiology 2000; Summer: 121-130.
6) Blair S et al, Am J Cardiology 2000; 86: 46-52.
7) Hendriks HF et al, Eur J Clin Nutr 1999; 53: 319-327.
8) Jones PJ et al, Am J Clin Nutr 1999; 69: 1144-1150.
9) Maki KC et al, Am J Clin Nutr 2001; 74: 33-43.
10) Miettinen TA et al, NEJM 1995; 333: 1308-1312.
11) Jones PJ et al, J Lipid Res 2000; 41: 697-705.
12) Gylling H and Miettinen TA, Metabolism 1999; 48: 575-580.
13) Hallikainen MA et al, J Nutr 2000; 130: 767-776.
14) US Federal Register 2000; 65: 54687-54739.
15) "FDA Authorizes New Coronary Heart Disease Health Claim for Plant Sterol and Plant Stanol Esters." FDA Talk Paper. September 5, 2000. Available at: http://www.cfsan.fda.gov/~lrd/tpsterol.html
16) Vissers MN et al, Am J Clin Nutr 2000. 72: 1510-1515.
17) Christiansen LI et al, Eur J Nutr 2001, 40: 66-73.
18) Pollack OJ and Kritchevsky D, Sitosterol. Monographs on Atherosclerosis, Vol. 10. S. Karger, New York, 1981.
19) "FDA Letter Regarding Enforcement Discretion With Respect to Expanded Use of an Interim Final Rule About Sterol/Stanol Esters and Reduced Risk of Coronary Heart Disease." February 14, 2003. Available at: http://www.cfsan.fda.gov/~dms/ds-ltr30.html
20) Gylling H et al, Atherosclerosis 1999; 145: 279-285.
21) Nguyen T, J Nutr 1999; 129: 2109-2112.
22) Noakes et al, Am J Clin Nutr 2002; 75:79-86.
23) Lichtenstein AH and Deckelbaum MD, Circulation 2001; 103: 1177-1179.

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