Herbs & Supplements:
Stanols

Supplement Forms / Alternate Names
  • Phytostanols, Sitostanol, Campestanol, Stigmastanol, 5-Alpha-Stanols, Stanol Esters
Principal Proposed Uses
  • Lowering Cholesterol

Stanols are substances that occur naturally in various plants. Their cholesterol-lowering effects were first observed in animals in the 1950s. Since then, a substantial amount of research suggests that plant stanols (modified into stanol esters) can help to lower cholesterol in individuals with normal or mildly to moderately elevated cholesterol levels. Stanols are available in margarine spreads, salad dressings, and dietary supplement tablets.

Requirements/Sources

Stanols occur naturally in wood pulp, tall oil, and soybean oil. Stanols are also made commercially from related substances in plants called sterols, such as beta-sitosterol.^1,2

For incorporation into foods, stanols are processed with fatty acids from vegetable oils to form chemicals called stanol esters.³ Plant stanol esters are found in margarine spreads and salad dressings, and are also available as dietary supplement tablets.

Therapeutic Dosages

Typical dosages of stanol esters to lower cholesterol levels range from 3.4 to 5.1 g per day.⁴ One manufacturer of a commercially prepared margarine spread recommends taking 3 teaspoons (1.5 g of sitostanol ester per teaspoon) per day. The suggested use varies depending on the product and the quantity of sitostanol ester per serving. One study suggests that using stanol products once a day may be as effective as dividing up your intake throughout the day.⁵ It may take up to 3 months to show a substantial decrease in total cholesterol values.⁶

Therapeutic Uses

Strong evidence tells us that stanol esters and related sterols can significantly improve cholesterol levels.^7–20

What Is the Scientific Evidence for Stanols?

Plant stanol esters reduce serum cholesterol levels by inhibiting cholesterol absorption.²¹ Because they are structurally similar to cholesterol, stanols can displace cholesterol from the "packages" that deliver cholesterol for absorption from the intestines to the bloodstream.²² The displaced cholesterol is not absorbed and is excreted from the body; the stanols themselves are ultimately not absorbed either.

At least 13 double-blind placebo-controlled studies, ranging in length from 30 days to 12 months and involving a total of more than 1,000 individuals, have found stanols or sterols effective for improving cholesterol levels.^23–36 The combined results suggest that stanols can reduce total cholesterol and LDL ("bad") cholesterol by about 10 to 15%. Stanols did not have any significant effect on HDL ("good") cholesterol or triglycerides in most of these studies.³⁷ However, when combined with a standard cholesterol-lowering diet, use of a spread enhanced with plant sterols improved total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides as compared to a normal reduced-fat spread.³⁸

In one of the best of the double-blind placebo-controlled studies, 153 individuals with mildly elevated cholesterol were given sitostanol esters in margarine (at 1.8 or 2.6 g of sitostanol per day), or margarine without sitostanol ester, for a total of 1 year.³⁹ The results in the treated group receiving 2.6 g per day showed improvements in total cholesterol by 10.2% and LDL cholesterol by 14.1%—significantly better than the results in the control group. Neither triglycerides nor HDL cholesterol levels were affected.

Two studies found stanols to be helpful for lowering cholesterol levels in individuals with type 2 (adult-onset) diabetes.^40,41 One of these studies examined two treatments: pravastatin (a cholesterol-lowering drug) versus pravastatin along with sitostanol. The combination treatment was more effective at lowering total cholesterol and LDL cholesterol levels than the drug treatment alone.⁴² Additive benefits were also seen in a study of nondiabetics taking statin drugs who began taking stanols as well.⁴³

Safety Issues

Stanols are considered safe because they are not absorbed.^44,45 No adverse effects have been reported in any of the studies on lowering cholesterol, with the exception of one study that reported mild gastrointestinal complaints in a few preschool children.⁴⁶ In addition, no toxic signs were observed in rats given stanol esters for 13 weeks at levels comparable to or exceeding those recommended for lowering cholesterol.⁴⁷

Although concerns have been expressed that stanols might impair absorption of the fat-soluble vitamins A, D, and E, this does not seem to occur at the dosages of stanols required to lower cholesterol.⁴⁸ Stanols might, however, interfere with absorption of alpha- and beta-carotene,^49,50 although some studies have found no such effect.^51,52 Until more is learned, it may be reasonable for individuals using stanol products to make sure to consume carotenoid-rich vegetables (yellow/orange and dark green vegetables).⁵³

Last reviewed March 2002 by Medical Review Board

Back to Top