Do Plant Sterols Reduce Cholesterol?

Plant sterols are a fascinating compound found in plants which have an amazing role in the reduction of the “bad cholesterol”, or LDL. They occur naturally in many foods and are often added to foods to make them healthier (such as margarine, orange juice and cereals). 

In this article we’ll learn what plant sterols are, their effects on cholesterol, and how you can incorporate them into your diet.Jump to:

• What are plant sterols?
• Plant sterols sources
• How do plant sterols affect cholesterol?
• Are plant sterols anti-oxidants?
• Age and plant sterols
• Plant sterols side effects

 

What are plant sterols?

Plant sterols, or phytosterols, are plant-based alcohol compounds. There are 40 different plant sterols identified¹, with more than 200 forms and related compounds found in plant and marine life². 

For clarity, the term stanol (rather than sterol) is used to describe saturated sterols which have no double bond in their sterol ring structure. 

The most commonly seen plant sterols are sitosterol, campesterol and stigmasterol; all of which are 4-desmethyl sterols (meaning they have no methyl groups attached to their carbon atoms)^1,3. 

They also are very structurally similar to the most common animal sterol, cholesterol. The similarity is that all sterols have a chemical ring structure, and differences are between the side chains attached to this ring¹. 

They also resemble cholesterol in their primary biological functions, and it’s these similarities which give phytosterols some of their health benefits. 

Due to their length being virtually identical to that of the phospholipid monolayer which creates a membrane around all cells (2.1nm)⁴, these compounds fit easily into these cell membranes. In fact, they have an important role in a number of functions for the cell membrane, such as cell stability and temperature management^3,5,6. 

Outside the cell membranes, they’re found predominantly in the outer layers of the mitochondria (biochemical powerhouse of the cell) and the endoplasmic reticulum (involved in protein and lipid synthesis)³.A final function of plant sterols which differentiates them from the animal sterol cholesterol, is their role in being a precursor for a number of plant growth factors³.

 

Plant sterols sources 

An average diet provides about 0.25g of plant sterols daily, which is doubled if you follow a vegetarian diet¹. 

In fact, a vegetarian diet can give up to 1g per day of plant sterols³. 

On average the intake of plant sterols is between 0.15-0.4g per day^7,10,12,14, and approximately 10% comes from consumption of plant stanols.

 

Vegetable oils and fats 

In the UK, vegetable oils, fats and products derived from oils are considered the richest source of natural plant sterols³. The daily estimated intake from oils of the most common sterols was 44% sitosterol, 54% stigmasterol and 59% campesterol³.

 

Cereals, grains and nuts

The next most abundant source of plant sterols are cereals, grains and nuts³, with amounts of sitostanol and campestanol in products like wheat and rye⁹. In fact, bread and cereals make up approximately 36% of sitosterol intakes¹⁰. 

As well as these natural sources, sterols can also be added to other food products (for example margarine)¹¹. 

Further sources of plant sterols (including brassicasterol, avenasterol and campesterol) include shellfish, like clams and oysters^13,15. 

 

How do plant sterols affect cholesterol?

Plant sterols and cholesterol

While it’s assumed that plant sterols lower cholesterol general, the essence is the amount of plant sterols consumed in diet reduces the levels of LDL-cholesterol³. 

Remember, the greater the amount of LDL-cholesterol consumed, the greater the risk of cardiovascular and circulatory diseases^16,17. 

Research into the health benefits of plant sterols has a long history going back 60 years to the 1950s where a crystalline form of these sterols was used to lower cholesterol levels in those with high cholesterol^18,19.

The mechanism by which they do this is through reducing the absorption of cholesterol from the gut. Their similar structure is well suited to compete with cholesterol to replace them in the packages formed in the intestines which deliver lipids to cells^20,24; leaving cholesterol to be removed as waste. 

Research further developed in the 1970s where sitostanol and campestanol were shown to be the most effective form of this compound³. 

20 years later, after stanol esters were formulated and found to reduce lipid levels in people with high cholesterol, the inclusion of such esters into mayonnaise and margarine showed a consistent reduction of cholesterol by 10-15%²⁵. This reignited the research into plant sterols leading to the production of a variety of different food stuffs which had added sterols.Learn more about cholesterol here...