Can Taking Phytosterol Supplements Cause Side Effects?

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Studies have shown that phytosterols, also known as plant sterols, can help slightly lower your LDL cholesterol. Phytosterols function by lowering the absorption of LDL cholesterol from the small intestine into the blood. They are naturally found in many healthy foods in varying amounts, including:

  • Whole grains
  • Soybeans
  • Fruit
  • Vegetables
  • Mushrooms
  • Lentils
  • Nuts

Some commercially prepared foods – such as juices, yogurt, breakfast bars, salad dressings, and spreads – are fortified with phytosterols during the manufacturing process.

Phytosterol-containing supplements are also widely available in many health foods stores, grocery stores, and pharmacies.

Current studies suggest that you should ingest anywhere between 1 and 3 grams of phytosterols daily in order to reduce LDL cholesterol by at least 10%. Because following an exclusively vegetarian diet only yields up to roughly 750 grams of phytosterol intake daily, it may be tempting to use supplements to lower your LDL cholesterol levels.  Although they appear to be convenient, it does not necessarily mean that they cannot cause any side effects.

Side Effects Associated with Phytosterols

From the studies that have been conducted so far examining use of phytosterol supplements, they appear to be well-tolerated. However, there have been some side effects that have been reported with their use in some studies. These side effects – mostly affecting the gastrointestinal tract - include:

  • Constipation
  • Nausea
  • Upset stomach
  • Heartburn
  • Fecal discoloration
  • Flatulence
  • Appetite changes

In most cases, these side effects appear to be mild and usually disappear with continued use. In some cases, however, these side effects may be uncomfortable enough to cause you to discontinue taking the supplement.

The side effects experienced appear to be associated with higher doses.

It is also not fully known if phytosterol supplements can interact with any other medications or supplements you are taking. Currently, there have not been many drug interactions reported between phytosterol supplements and other products. The cholesterol-lowering drug, cholestyramine, may reduce the effectiveness of phytosterol supplements. Therefore, your supplement should be taken a few hours before or after you take cholestyramine. A couple of studies suggest that phytosterol supplementation may reduce the absorption of the vitamin, beta-carotene. In one study, beta-carotene supplementation – or consuming foods rich in beta carotene – may circumvent this.

The Bottom Line

Although there has been some promising research examining the use of phytosterol-containing supplements in lowering LDL cholesterol levels, their side effects have not been fully investigated. Because studies examining phytosterol supplements have only been conducted over a short period of time, it is unknown what side effects could be experienced when taking phytosterol supplements over a long period of time.

Therefore, if you would like to add phytosterol supplements to your cholesterol-lowering plan, you should discuss it with your healthcare provider.

Alternatively, incorporating healthy, phytosterol-containing foods into your cholesterol-lowering diet is another way you can introduce phytosterols. Foods naturally containing phytosterols are usually plentiful in other nutrients - such as fiber and antioxidants - that can keep your lipid levels healthy.

Sources:

AbuMweis SS, Marinangeli CPF, Frohlich J et al. Implementing phytosterols into medical practice as a cholesterol lowering strategy: overview of efficacy, effectiveness and safety. Can J Cardiol 2014; 30:1225-1232.

Clifton P. Lowering cholesterol: a review of the role of plant sterols. Aus Fam Phys 2009; 38:218-222.

Malinowski JM and Gehret MM. Phytosterols for dyslipidemia. Am J Health Syst Pharm 2010; 67;1165-1173.

Micromedex Healthcare Series [internet database]. Greenwood Village, CO: Thomson Reuters (Healthcare) Inc. Updated periodically.

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