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.

VIEW OUR ONLINE HEALTHY CHOLESTEROL LIFESTYLES RESOURCE CENTRE

References
1. Emberson JR, Whincup PH, Morris RW, Walker M. Re-assessing the contribution of serum total cholesterol, blood pressure and cigarette smoking to the aetiology of coronary heart disease: impact of regression dilution bias. Eur Heart J 2003; 24: 1719–26.
2. The British Heart Foundation Statistics Website.
3. Law MR, Wald NJ, Thompson SG. By how much and how quickly does reduction in serum cholesterol concentration lower risk of ischaemic heart disease? BMJ 1994; 308: 367-72.
4. Baigent C, Keech A, Kearney PM, Blackwell L, Buck G, Pollicino C, Kirby A, Sourjina T, Peto R, Collins R, Simes R; Cholesterol Treatment Trialists' (CTT) Collaborators. Efficacy and safety of cholesterol-lowering treatment: prospective meta-analysis of data from 90,056 participants in 14 randomised trials of statins. Lancet 2005; 366: 1,267-78.
5. Jenkins DJ, Kendall CW, Faulkner DA, Nguyen T, Kemp T, Marchie A, Wong JM, de Souza R, Emam A, Vidgen E, Trautwein EA, Lapsley KG, Holmes C, Josse RG, Leiter LA, Connelly PW, Singer W. Assessment of the longer-term effects of a dietary portfolio of cholesterol-lowering foods in hypercholesterolemia. Am J Clin Nutr 2006; 83: 582-91.
6. Katan MB, Grundy SM, Jones P, Law M, Miettinen T, Paoletti R; Stresa Workshop Participants. Efficacy and safety of plant stanols and sterols in the management of blood cholesterol levels. Mayo Clin Proc 2003; 78 (8): 965-78.
7. Ortega RM, Palencia A, López-Sobaler AM. Improvement of cholesterol levels and reduction of cardiovascular risk via the consumption of phytosterols. Br J Nutr 2006; 96 Suppl 1: S89-93.
8. Law M. Plant sterol and stanol margarines and health. BMJ 2000; 320: 861-4.
9. Castro Cabezas M, de Vries JH, Van Oostrom AJ, Iestra J, van Staveren WA. Effects of a stanol-enriched diet on plasma cholesterol and triglycerides in patients treated with statins. J Am Diet Assoc 2006; 106 (10): 1,564-9.
10. Martikainen JA, Ottelin AM, Kiviniemi V, Gylling H. Plant stanol esters are potentially cost-effective in the prevention of coronary heart disease in men: Bayesian modelling approach. Eur J Cardiovasc Prev Rehabili 2007; 14(2): 265-72.

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