Cholesterol - the Facts

Plant Sterols

The Role of Plant Sterols

What are plant sterols?

Plant sterols are natural compounds that maintain cell membrane structure and function in plants. In this way they have a very similar function to cholesterol in humans, and are also structurally similar. The most common plant sterols are beta-sitosterol, campesterol, and stigmasterol.

Where are plant sterols found?

Plant sterols are found naturally in everyday foods like vegetable oils, nuts, seeds, grain products, fruit and vegetables as well as in fortified products.

Why do we need plant sterols?

Many dietary factors affect LDL-cholesterol levels. Making positive dietary changes including replacing saturated fats with polyunsaturates and keeping intakes of trans fats to a minimum are well known to lower LDL-cholesterol1.

However, the most effective way to lower LDL-cholesterol with dietary change is to include plant sterols2. Eating 2-3 g of plant sterols daily can lower LDL-cholesterol by up to 15% when combined with the move to a healthy diet and lifestyle.

Epidemiological and intervention studies estimate that on average lowering cholesterol by 10% will reduce the risk of CHD by up to 20%3.

Plant sterols reduce cholesterol absorption

The key benefit of plant sterols lies in their ability to reduce the absorption of cholesterol from the gut into the blood stream.

Cholesterol is an essential building block in the human body and plays a key role in maintaining cell membranes. It is naturally produced in the liver but is also delivered through foods containing cholesterol in the diet. As a part of normal metabolism, cholesterol in the gut mixes with bile salts, lecithin and triglycerides to form micelles. Micelles then deliver cholesterol to the cells lining the gut wall where the cholesterol is re-packaged and released into the bloodstream.

Plant sterols have a similar chemical structure to cholesterol. It is thought that when plant sterols reach the gut, they displace cholesterol from the micelles4. In this way, less cholesterol reaches the lining of the gut wall in a form that can be absorbed.

Consuming 2g of plant sterols a day reduces the absorption of cholesterol by 30-40%. The cholesterol that is not incorporated into the micelles is then excreted (along with virtually all the plant sterols). In this way, cholesterol is removed from the body. Subsequently, levels of LDL-cholesterol are lowered but HDL-cholesterol and triglyceride levels remain unaffected.

What evidence is there for the cholesterol-lowering efficacy of plant sterols?

Since the late 1980s, Unilever, in collaboration with many independent scientific investigators, has extensively researched the cholesterol-lowering properties of plant sterols. There are currently over 170 clinical studies published in peer reviewed journals, proving the cholesterol-lowering efficacy of plant sterols.

What amount of plant sterols is needed for maximum cholesterol lowering?

There is a continuous dose-response relationship between the intake of plant sterols and their effect on LDL-cholesterol levels5,6. The more plant sterol consumed, the greater the reduction in LDL-cholesterol up to about 2-2.5g plant sterol per day. Intakes above 3g/day are not recommended as this provides little further benefit2.

Do international dietary guidelines include plant sterols?

The National Heart Foundation of Australia and New Zealand, and many international organisations including the International Atherosclerosis Society, the American Heart Association, Dutch Heart Foundation, Finnish Nutrition Association, Finnish Medical Society, Spanish Atherosclerosis Society and Nutrition Foundation of Italy have all included plant sterols in their dietary recommendations for cholesterol management.

Are plant sterols safe for consumption?

Since plant sterols are naturally present in most vegetables, they have been consumed for a long time and are known to be safe. The safety of high intakes of plant sterols has been studied extensively since the 1950s and reviewed by independent experts and regulatory authorities internationally, which have all found them to be safe.

What is the clinical application of plant sterols?

Plant sterol-enriched foods are recommended to be consumed as part of a healthy balanced diet low in saturated fat and high in fruit and vegetables. They are effective for people:

  • on lipid-lowering medications such as statins and fibrates7,10
  • with elevated blood cholesterol levels
  • with Type 2 diabetes8,10
  • with familial hypercholesterolaemia9,10

The role of healthcare professionals

Healthcare professionals have a key role to play in helping patients select a heart healthy diet. Those patients with raised cholesterol are likely to benefit from including plant-sterol enriched foods as part of their healthy diet and lifestyle for a healthier heart.