Are Plant Sterols Important to My Diet?

If you or your clients are concerned about lowering your blood cholesterol levels, you probably need to know more about plant sterols, also known as phytosterols.

Plant sterols occur naturally in a host of foods—primarily soybean oil, nuts, seeds, legumes and some fruits and vegetables. Because plant sterols are chemically similar to cholesterol, the human body tends to absorb them and pass cholesterol out of the body as waste. The net result is that consuming foods rich in plant sterols can reduce the body’s blood cholesterol levels.

The U.S. Food and Drug Administration (FDA) allows food companies to declare the heart benefits of plant sterols on product packaging. That suggests lots of consumers may arrive in your studio or facility with questions about what sterols are, how they work and how to include them in their diet.

The Science of Sterols

Plant sterols are neither a fad nor a flavor of the week; they offer a scientifically sound way to reduce both total blood cholesterol and LDL (bad) cholesterol, or LDL-C. Published research has found that consuming an adequate amount of plant sterols each day can lower total blood cholesterol by an average of 6%–10% and lower LDL-C 6%–15% (Hallikainen, Sarkkinen & Uusitupa 2000; Volpe et al. 2001; Devaraj, Jialal & Vega-Lopez 2004).

Most of us are already eating sterols. A typical Western diet averages 150–400 milligrams (mg) per day, while a typical vegetarian diet averages about 600 mg per day (Katan et al. 2003). Many foods can reduce cholesterol; they just are not very good at it. For instance, I have calculated that a person would have to eat 51 cups of broccoli, or 83 oranges, or 16 cups of peanuts, every day to reduce their LDL-C by 6%–15%. In contrast, people can achieve those 6%–15% reductions by consuming just small amounts of sterol-rich foods.

Scientists have known about the cholesterol-reducing properties of plant sterols since the early 1950s (Peterson, Nichols & Shneour 1952; Pollak 1953), but the secret of improving the solubility of sterols so they could be more easily incorporated into our diets eluded researchers for four decades. The riddle was solved in the early 1990s (Miettinen et al. 1995), and since then a wide range of foods—such as spreads, juices, pasta products, milk and bread fortified with plant sterols—has become available to consumers.

Recent studies offer good guidance on how much of these foods we should add to our diets. A large body of published research indicates that taking 2–3 grams (g) (0.07–0.11 ounces) of plant sterols a day can lower LDL-C by 6%–15% (Hallikainen, Sarkkinen & Uusitupa 2000; Volpe et al. 2001; Devaraj, Jialal & Vega-Lopez 2004; Davidson et al. 2001; Vanstone et al. 2002). More recently, a review of 84 trials (Demonty et al. 2009) showed that an average intake of 2.15 g per day reduced LDL-C by 8.8% (Miettinen et al. 2000; Goldberg et al. 2006). Translation: If a client’s LDL-C was 100, consuming plant sterols could lower that number to 91.

Sterols can also work in concert with prescription medications. For example, if a person is already taking a statin medication to lower LDL-C levels, plant sterols will continue to reduce cholesterol levels by 4.5% per gram of sterol. So taking 2 g of plant sterols per day could lower your LDL-C by about 8%–9% on top of the reduction from the medication.

Note that sterols work only up to a certain point; after that, the effectiveness wears off. A number of studies have demonstrated that the optimal intake of plant sterols is around 2 g per day and intakes above 2.5 g show little added benefit (Katan et al. 2003). The effect of regular consumption of plant sterols on cholesterol reduction can be measured in 3–4 weeks (Miettinen et al. 1995; Volpe et al. 2001).

Now on Food Labels

Because of the science supporting plant sterols as cholesterol reducers, the FDA has authorized companies to make specific health claims for foods that contain sterols. As of February 2012, this is how the health claim reads:

“Foods containing at least 0.5 g per serving of phytosterols eaten with meals or snacks for a total intake of 2 g, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease” (AND 2011).

Food companies that comply with the guidelines of this claim can print it on their food labels. The claim will also include the name of the food product and how many grams of plant sterols the food contains.

Two prominent organizations support the 2-gram-per-day recommendation: the National Cholesterol Education Program’s Adult Treatment Panel III, in its Therapeutic Lifestyle Change diet (NCEP 2002); and the American Heart Association, in its 2006 Diet and Lifestyle Recommendations Revision (Lichtenstein et al. 2006).

Functions and Risks

Plant sterols can reduce cholesterol because they are structurally similar to the cholesterol that is either made by the body or occurs in foods. Sterols block the absorption of cholesterol from the intestinal tract, thereby reducing the amount of cholesterol the body absorbs (Plat & Mensink 2005). The cholesterol that is not absorbed is eliminated.

The safety of consuming plant sterols to lower cholesterol has been studied extensively since the 1950s, when sterols were used in early cholesterol-lowering medications. In 1999, the FDA completed a comprehensive safety review of plant sterols and awarded GRAS (Generally Recognized as Safe) status for the use of these compounds in a number of different products (FDA 2011).

Researchers were concerned that plant sterols might reduce the absorption of certain fat-soluble vitamins, especially beta carotene, alpha carotene and vitamin E. Studies have demonstrated that this effect is not very significant (Clifton et al. 2004; Ntanios, Homma & Ushiro 2002) and that consumption of the recommended five servings or more of fruits and vegetables corrects the potential side effect (Noakes et al. 2002).

There have been other concerns regarding the potential adverse effects of plant sterols in certain persons who are hyperabsorbers (Weingartner, Bohm & Laufs 2009). Sitosterolemia, a rare genetic disorder, is characterized by increased intestinal absorption and decreased biliary excretion of dietary sterols (Bhattacharyya & Connor 1974). It is an exceedingly rare disorder that affects less than one patient in a million, with about 20 cases reported so far in the United States (Patel 2008). Individuals diagnosed with this disorder should not take plant sterols.

Consumers and health professionals can identify foods that contain plant sterols by looking for the health claim on labels and by checking package information for the amount of plant sterols in the food. Plant sterols are natural compounds—backed by science—that can help lower your cholesterol levels significantly. Discover foods containing plant sterols in your grocery store today.