Plant Sterols: Lower Cholesterol by Eating More Fat
When we think of lowering cholesterol, usually that means eating less fat. An exception to the rule is plant sterols and stanols--fats that can lower cholesterol.
The Basics on Sterols and Stanols
Sterols are building blocks for cells: The basic structural unit of living organisms. Cholesterol is the sterol found in animals. In addition to cells, it is converted into hormones and into bile which we use to absorb fats. We absorb about half the cholesterol we consume and that amount accounts for only a small portion of the cholesterol in our blood. Most of our blood cholesterol is made in our livers.
The cells of plants have sterols, too; mostly sitosterol and sitostanol, but there are others. A stanol is a sterol that is saturated; like a saturated fat. When we eat plants, we absorb the sterols and stanols. In fact, in the intestine, plant sterols and animal sterols are absorbed by the same mechanism. The more plant sterols in our food, the more we absorb instead of cholesterol. Absorbing less cholesterol leads to lower blood levels.
Here’s the catch: there is so little of the various sterols in most plants that we cannot eat enough, even if we are vegetarians, to significantly lower our blood cholesterol level. So, scientists have developed a way to extract the sterols from plants and convert them into a more absorbable form that can be added to other foods already high in fat so that we may consume enough to get an effect.
For several years, sterol-fortified margarines, marketed to assist in reducing cholesterol, have been available. About 2-3 grams of plant sterols a day can reduce cholesterol about 10-15%. Two to three tablespoons of these margarines provide the necessary amount of sterols.
In recent years, plant sterols have been added to other high-fat foods, including chocolate candy (CocoaVia®), yogurt, cheese, bread, and granola bars. High-fat foods can deliver more sterols per ounce because the fatty sterols are just part of the regular fat content. One brand of orange juice has sterols added, but to get the amount of sterols in two tablespoons of cholesterol-lowering margarine, you would have to drink more than a quart of juice.
Sterol-Fortified Foods and the Impact on Your Cholesterol Levels
Are plant sterols powerful enough to lower cholesterol without using drugs? The answer is, unfortunately, probably not for most people with high cholesterol. Someone with an LDL (or “bad” cholesterol) of 160 whose goal is an LDL of 100 requires a 38% reduction in LDL, so plant sterols are not enough. However, they can provide additive effects to prescription medications. Many physicians think that even people with no history of heart disease and relatively normal cholesterol levels could reduce their risk of atherosclerosis if their cholesterol is even a little lower. The benefit, if any, of using plant sterols would be small, but since we often do not realize our actual risk of atherosclerosis until it develops, it seems reasonable to use these sterol-fortified foods even with normal cholesterol levels. However, long-term studies on the health benefits in those with normal cholesterol have not been completed at this time.
There is a rare genetic condition, homozygous sitosterolemia, that might be worsened by high sterol content foods, but that is controversial. There are no studies proving safety of these foods in children or pregnant women. Hypothetically, large amounts of plant sterols could reduce the amount of fat soluble vitamins absorbed, but there is no consensus on that yet.
Foods that contain large amounts of plant sterols and stanols include sesame seeds (about 700 mg per 3 oz. serving), wheat germ (about 400 mg per 3 oz.), and peanuts (about 220 mg per 3 oz. serving). Most other vegetables and seeds have far less. Even a vegetarian is unlikely to consume more than one gram of plant sterols and stanols in a day – less than half the 2-3 grams required to lower cholesterol. Additionally, the sterols are not easily absorbed until they are changed or esterified for better absorption as they are in sterol-fortified foods.
People with high cholesterol should not undertake the use of plant sterol-fortified foods to reduce their cholesterol levels without consulting their physicians to be certain they are reaching their cholesterol goals. Most will still need a prescription medication, but plant sterols can help as part of a comprehensive plan that includes a proper diet and exercise regimen.
1. http://www.ific.org/publications/factsheets/sterolfs.cfm. Accessed 30 November 2007.
2. Plat J., Mensink RP. Plant stanol and sterol esters in the control of blood cholesterol levels: mechanism and safety aspects. Am. J. Cardiol. 2005 Jul 4;96(1A):15D-22D.
3. Lichtenstein, AH, et al. Stanol/Sterol Ester-containing foods and blood cholesterol levels. Circulation. 2001;103:1177.
4. Katan MB, et al. Efficacy and safety of plant stanols and sterols in the management of blood cholesterol levels. Mayo Clin. Proc. 2003 Aug;78(8):965-78.
5. http://www.benecol.net/healthcareprofessionals.asp?viewID=2369# . Accessed 1 December 2007.