Plant Sterols: Natural Compounds That Lower Cholesterol
Plant sterols (phytosterols) are naturally occurring compounds found in all plant-based foods that compete with cholesterol for intestinal absorption, thereby reducing cholesterol levels in the bloodstream. 1
Structure and Mechanism of Action
Plant sterols are structurally similar to cholesterol but contain additional methyl or ethyl groups 2. Their cholesterol-lowering effect works through several mechanisms:
- They displace cholesterol from intestinal micelles, reducing the pool of absorbable cholesterol 3
- They decrease cholesterol content of micelles and reduce its transport toward the intestinal brush border membrane 4
- They may interfere with transporter-mediated processes of cholesterol uptake via NPC1L1 protein and ABCG5/ABCG8 transporters 4
- They are poorly absorbed themselves, with minimal elevation in plasma levels after ingestion 4
Effectiveness for Cholesterol Management
- Consumption of 2 g/day of phytosterols decreases LDL-C by 5-15% 4
- Daily intake of 2-3 g has been reported to decrease total and LDL cholesterol levels by 9-20% 4, 1
- The cholesterol-lowering effect plateaus at doses above 3 g/day 4, 1
- Plant sterols have minimal to no effect on HDL cholesterol or triglyceride levels 4
Forms and Administration
Plant sterols are available in two main forms:
- Plant sterol esters
- Plant stanol esters (hydrogenated form of plant sterols)
Both forms appear to lower LDL cholesterol equivalently when consumed in their unesterified form 5. The FDA has approved health claims for both forms:
- For plant sterol esters: Foods containing at least 0.65 g per serving, eaten twice daily for a total intake of at least 1.3 g, may reduce heart disease risk 4
- For plant stanol esters: Foods containing at least 1.7 g per serving, eaten twice daily for a total intake of at least 3.4 g, may reduce heart disease risk 4
Safety and Considerations
- Plant sterol esters have "generally recognized as safe" (GRAS) status in the U.S. 4
- Potential side effects include mild bloating, diarrhea, or constipation 4
- Some concern exists regarding decreased absorption of fat-soluble vitamins and carotenoids 4
- There is a potential safety concern regarding phytosterol consumption in patients with phytosterolemia (a rare genetic disorder) 4
Natural Sources vs. Supplements
- The average human consumption of plant sterols from natural foods is approximately 150-350 mg/day 1
- Vegetables contain approximately 14 mg/100g (range 3.8-50 mg/100g) 1
- This natural intake is well below the therapeutic dose needed for significant cholesterol reduction 1
- For therapeutic effects, specialized plant sterol-enriched foods or supplements are typically required 1
Clinical Application
While plant sterols effectively lower LDL cholesterol, cardiovascular outcome trials demonstrating reduction in morbidity and mortality have not been conducted 4. They are generally well-tolerated and represent a practical dietary approach to cholesterol management that can complement other lipid-lowering strategies.