We eat plants for the vitamins, minerals, and fiber they offer. Plus, plants contain natural compounds called phytonutrients that have potential health benefits that extend beyond the nutritional value they offer. For example, some phytonutrients, have anti-inflammatory and antioxidant properties. A number of plants, particularly nuts, beans, seeds, grains, and vegetables, also contain another component called plant sterols. Some food manufacturers now add plant sterols to packaged foods, like margarine, so they can advertise that the product has potential health benefits. What are plant sterols, and can they really improve your health?
If you cruise the supermarket aisle and read labels on containers of yogurt, mayonnaise, margarine, orange juice, or breakfast cereal, you may see that some contain plant sterols. One of the first types of packaged food that contained plant sterols was margarine. We now know that margarine is not a healthy substitute for butter as most margarine contains trans-fat, but manufacturers market their margarine as hearty healthy based on the plant sterols added to the product. But, now you can find them in other packaged foods as well. Some, like yogurt, don’t carry the same health stigma that margarine does.
How Plant Sterols Work
What’s the point of consuming plant sterols anyway? Assuming you consume them in sufficient quantities, they block the absorption of cholesterol from the foods you eat. Studies show that they help lower LDL-cholesterol, the form of cholesterol linked with cardiovascular disease. But, you’d have to eat a lot of foods containing plant sterols to see a significant reduction in LDL-cholesterol.
Natural plant-based foods, like nuts, vegetables, cereals, legumes, and nuts contain only small quantities of these compounds, not enough to have a major impact on lipid levels. However, foods fortified with plant sterols, like yogurt and orange juice, have higher levels because they’ve been added to the product. For example, one brand of orange juice fortified with plant sterols contains almost a gram of plant sterols in each glass. You need two or more grams daily to have an impact on your benefits. So, drinking two glasses daily would conceivably offer theoretical benefits.
What are the Potential Benefits?
Plant sterols are similar in structure to the cholesterol that your body produces and gets through diet. Because they resemble cholesterol, they disrupt normal absorption of cholesterol through the digestive tract. Although they aren’t well absorbed by the digestive tract either, some can enter the body.
Do they work? A meta-analysis of 59 randomized controlled trials found that plant sterols can lower LDL-cholesterol between 5 and 15%. This is not a huge drop, but it is enough to reduce the risk of heart disease based on current risk scales. The analysis found that reductions in LDL-cholesterol were greatest when subjects consumed them in fatty foods, like mayonnaise, salad dressing, and yogurt and when they ingested them throughout the day rather than getting a single dose in the morning. In the study, people who had a higher LDL-cholesterol initially experienced the greatest reduction.
Are there any drawbacks to adding plant sterols to your diet? One concern is that they could have some of the negative effects that cholesterol has. For example, plant-based sterols could theoretically attach to the walls of arteries, as cholesterol does. In one study, researchers found that these plant fats did accumulate in the aortic valve of the heart, raising the question as to whether they themselves cause heart disease. Reassuringly, a review of multiple studies by the European Heart Journal didn’t correlate blood levels of plant sterols with a higher risk of cardiovascular disease. However, it’s still not clear whether it’s safe to consume high concentrations of plant sterols long-term.
Another concern is that they could interfere with the absorption of some vitamins, particularly those that are fat-soluble. In fact, research suggests that plant sterols reduce the absorption of carotenoids, antioxidants in orange fruits and vegetables as well as greens, by as much as 15%. Another concern is the type of foods that they are in. While yogurt is a healthy option, margarine and many breakfast cereals that contain plant sterols are not. Even orange juice with plant sterols isn’t necessarily a “good-for-you” choice if you have diabetes or pre-diabetes. The sugar content is too high. You can’t get enough plant sterols to lower your cholesterol from natural sources.
As you might expect, companies now market plant sterol supplements in pill form. That would be an easy way to get these plant-based fats, but there’s not enough evidence that plant sterol supplements have the same impact as plant sterols you find naturally in foods.
Should You Eat Plant Sterol Fortified Foods?
If you have high cholesterol, you might be tempted to add plant sterol fortified foods to your diet, but don’t choose packaged products just because they contain plant sterols. Be sure it’s a healthy packaged product, like yogurt, rather than margarine that contains unhealthy fats. Even then, the impact on your cholesterol will likely be modest. Also, we now know that inflammation may play a more important role in heart disease than cholesterol. Make sure you’re eating a variety of whole foods with lots of fruits and vegetables, to help keep inflammation in check.
As far as lowering elevated cholesterol, talk to your physician about your options and monitor your other risk factors for cardiovascular disease as well – a large waist size, elevated blood pressure, lack of physical activity, and a high or borderline-high blood sugar level.
The Bottom Line?
Plant sterols may modestly reduce your LDL-cholesterol if you consume foods enriched with them regularly. However, foods that contain added plant sterols aren’t always a healthy choice. You might be better served eating a varied diet rich in a variety of plant-based foods. Foods that naturally contain plant sterols tend to be rich in other vitamins and minerals and contain fiber as well. So, enjoy these foods, but don’t go overboard with foods fortified with them as not all are healthy.
References:
Linus Pauling Institute. “Phytosterols”
BMJ. 2000 March 25; 320(7238): 861–864.
Food Nutr Res. 2008; 52: 10.3402/fnr.v52i0.1811.
The Journal of Nutrition, Volume 136, Issue 8, 1 August 2006, Pages 2135–2140, https://doi.org/10.1093/jn/136.8.2135.
The Journal of Lipid Research, 49, 1511-1518.
Eur Heart J. 2012 Feb; 33(4): 444–451. doi: 10.1093/eurheartj/ehr441.
