Online-only article: Plant stanols and sterols: a suitable adjunct to statin therapy?

Dr Frankie Phillips, a registered dietitian based in Devon and public relations officer for the British Dietetic Association looks at the evidence for the use of dietary therapies in lowering cholesterol

Blood cholesterol has a log-linear relationship to coronary heart disease (CHD); raised cholesterol is one of the key modifiable factors associated with risk of the disease and, alongside smoking and raised blood pressure, accounts for around 80 per cent of premature CHD.1

With prevalence of CHD increasing in the UK, the cost of treatment is set to rise. Already, lipid-lowering medication is the most costly class of drugs to the NHS.2

Statin therapy is known to be a very effective means of lowering cholesterol in patients who have raised levels, and studies suggest that these drugs typically lower LDL-cholesterol by 1.8mmol/l.3 Consequently, it has been suggested that statin therapy can safely reduce the five-year incidence of major vascular events by about 20 per cent for each 1mmol/l reduction in LDL-cholesterol.4

Statins are clearly effective at lowering LDL- and total cholesterol, but dietary therapies, either alongside or even in place of drugs (for example in patients who are unresponsive or those in whom statins are contraindicated), have been shown to demonstrate significant effects on lowering LDL-cholesterol and total cholesterol.

In particular a portfolio of foods, including almonds, soya, oats, soluble fibre and plant sterols and stanols, may have a similar degree of effect on cholesterol reduction as statin therapy.5

Although not intended as a substitute for drugs, studies have shown that those who comply with a range of dietary interventions experienced reductions in LDL-cholesterol of around 20 per cent.

Focus on dietary stanols and sterols
Sterols and stanols are naturally-occurring components, similar in chemical structure to cholesterol, found in plant-based foods including fruits, vegetables, oils, grains, nuts and seeds. However, at the levels in which they normally occur in the diet, there is no appreciable effect on cholesterol.

Through esterification, stanols and sterols are better absorbed by the body and, since the process makes them more fat-soluble, they can be incorporated into foods containing fat, such as dairy products and spreads.

How do they work?

Being similar in chemical structure to cholesterol, stanols and sterols have been demonstrated to lower blood cholesterol levels by reducing the absorption of cholesterol from the intestine. It has been suggested that sterols or stanols may compete with cholesterol for the limited space in the fat-transporting micelles. Another mechanism has shown that plant sterols and stanols may form crystals with cholesterol that cannot be absorbed and so are excreted. Consequently, more cholesterol is excreted via the faeces.

Cholesterol-lowering effects
There have been a number of studies that have clearly demonstrated the effects of plant sterols and stanols on cholesterol. In particular, one meta-analysis of 41 studies6 showed that taking a 2g per day dosage of plant sterols or stanols reduced LDL-cholesterol by a clinically significant 10 per cent after two to three weeks, consequently reducing cardiovascular risk for people with raised LDL-cholesterol.7,8

Research has further focussed on the effects of combining a diet containing stanol-enriched margarine with statin therapy. One study in particular9 showed that when patients on optimal statin therapy changed their diet, to include daily plant stanol-enriched margarine, low-density lipoprotein cholesterol decreased significantly by 15.6 per cent, compared with a reduction of only 7.7 per cent in the control group of statin users.

More recently, it has been demonstrated, using modelling techniques, that replacing usual margarine with one containing stanols reduced total cholesterol by 0.362mmol/l compared with 0.385mmol/l reduction when stanols were consumed alongside a statin.10 The authors recommended that plant stanol ester-containing spreads, used daily to replace regular spread, could be seen as a potentially cost-effective policy in men and older women with raised cholesterol levels.

It is important to note that the correct dose of stanols or sterols needs to be consumed, and manufacturers’ guidelines should be followed.

A dose of 2-3g per day is generally recommended, as there seems to be no further significant improvement if larger quantities are consumed (the dose effect curve levels off). Furthermore, the beneficial effect is lost when patients stop using the product. A dose of 2-3g can be obtained by consuming three portions of foods enriched with plant sterols or stanols such as margarines and dairy products (eg Benecol and Flora Pro-activ).

In light of the encouraging results from studies conducted to date, NICE has highlighted a research need to establish the effectiveness of plant sterols and stanols, recognising the potential of these products an appropriately adapted low-fat diet to avoid the need to use drugs to modify cholesterol levels.


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