What is the Difference Between Plant Stanols and Sterols

The main difference between plant stanols and sterols is that plant stanols are the saturated or reduced sterols similar to cholesterol but, with a methyl or ethyl group attached to the molecule whereas plant sterols are steroids with an alcohol group attached to the molecule. Furthermore, plant stanols have a comparatively lower degree of absorption whereas plant sterols have a higher degree of absorption in the intestine.  

Plant stanols and sterols are the two most effective ingredients found in food products that lower cholesterol levels in the blood. 

Key Areas Covered 

1. What are Plant Stanols
     – Definition, Structure, Importance
2. What are Plant Sterols
     – Definition, Structure, Importance
3. What are the Similarities Between Plant Stanols and Sterols
     – Outline of Common Features
4. What is the Difference Between Plant Stanols and Sterols
     – Comparison of Key Differences

Key Terms 

Cholesterol, LDL, Phytosterols, Plant Stanols, Plant Sterol, Steroids

What are Plant Stanols 

Plant stanols are one of the two types of phytosterols, which are the chemical compounds known to reduce low-density lipoprotein (LDL) cholesterol in the blood. Generally, phytosterols prevent the absorption of animal cholesterol in the intestine by competing with them. Therefore, they help to reduce the formation of atherosclerosis and heart disease, which are caused by animal cholesterol.

Figure 1: Cholesterol

Furthermore, plant stanols are a type of hydrogenated plant sterols. Also, they are esterified further by the fatty acids of plant origin. They are present in small quantities in fruits, vegetables, nuts, seeds, cereals, legumes, and vegetable oils.  

What are Plant Sterols 

Plant sterols are the second type of phytosterols. They are a type of steroid alcohols. Further, they have a similar structure to human cholesterol. Generally, the majority of unrefined vegetable oils contain 0.1–0.5% of plant sterols. Oils such as rice bran, wheat germ, and oat oil contain up to 4% (w/w) of plant sterols. Usually, the normal intake of these sterols can range from 200 to 400 mg per day while vegetarians have a higher daily intake of them.

Figure 2: β-Sitosterol 

Furthermore, the major plant sterols are β-sitosterol, campesterol, and stigmasterol. Moreover, some plant sterols occur in their free form while the majority of them (20% to 80% of the total intake) are esterified. Generally, a small amount of plant sterols may occur as glucosides.  

Similarities Between Plant Stanols and Sterols 

• Plant stanols and sterols are two naturally-occurring compounds with a similar structure to cholesterol. 
• Therefore, both are steroids. 
• Both are called phytosterols, which are the plant equivalent to animal cholesterol.  
• They are a type of essential components of the cell membrane of both animals and plants. 
• Also, they have a similar cellular function to human cholesterol. 
• Hence, both serve as effective ingredients in food, which lower cholesterol levels in the blood by preventing the absorption of real cholesterol into the bloodstream. 
• Moreover, both occur in many grains, vegetables, fruits, legumes, nuts, seeds, and vegetable oils in small quantities. 
• And, their free forms are poorly soluble in oil or water. 
• But, their esterified forms with polyunsaturated fatty acids show increased levels of solubility in vegetable oils. Thus, this is the reason for their extensive use in margarine and spreads, dressings, and yogurts.  
• However, large doses of plant sterols and stanols may cause nausea, indigestion and diarrhea, and interfere with the absorption of fat-soluble vitamins.  

Difference Between Plant Stanols and Sterols 

Definition 

Plant stanols refer to a heterogeneous group of chemical compounds known to reduce the level of low-density lipoprotein (LDL) cholesterol in the blood while plant sterols refer to the cholesterol-like substances that occur naturally at low levels in fruits, vegetables, nuts, and cereals.

Significance 

Furthermore, plant stanols are the hydrogenated form of plant sterols while plant sterols are the steroids with a similar structure to cholesterol. Thus, this is the main difference between plant stanols and sterols.

5-6 Bond 

The 5-6 bond of plant stanols is saturated while the 5-6 bond of plant sterols is unsaturated.  

Side Groups 

Another difference between plant stanols and sterols is their side groups. Plant stanols have either methyl or an ethyl group attached to the molecule while plant sterols have an alcohol group attached to the molecule. 

Absorption in the Intestine 

Moreover, plant stanols have comparatively a lower degree of absorption while plant sterols have a higher degree of absorption in the intestine. 

Conclusion 

Plant stanols are the hydrogenated form of plant stanols. They contain methyl or ethyl groups attached to them. Thus, it reduces the level of absorption of plant stanols in the intestine. On the other hand, plant sterols are steroids with a similar chemical structure to human cholesterol. Moreover, they have a higher level of absorption in the intestine. Nevertheless, both plant stanols and sterols are phytosterols. They are capable of reducing the amount of real cholesterol absorption in the intestine. Therefore, they help to reduce blood cholesterol levels or LDL levels, which can cause heart disease. However, the main difference between plant stanols and sterols is their chemical structure and the level of absorption in the intestine. 

References:

1. “Plant Stanols.” Plant Stanols – an Overview | ScienceDirect Topics, Elsevier B.V., Available Here.
2. Griffin, R. Morgan. “Plant Sterols and Stanols for Helping High Cholesterol.” WebMD, WebMD, Available Here.

Image Courtesy:

1. “Cholesterol” By BorisTM – own work (ISIS/Draw 2.5 –> MS Paint –> Infan View) (Public Domain) via Commons Wikimedia   
2. “Sitosterol structure” By User:Mysid – Self-made in BKChem + perl + vim. (Public Domain) via Commons Wikimedia