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% 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% 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, experience unwanted side effects 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 stanols and sterols, 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%.
Focus on dietary stanols and sterols
Stanols and sterols 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 stanols or sterols may compete with cholesterol for the limited space in the fat-transporting micelles. Another mechanism has shown that plant stanols and sterols may form crystals with cholesterol that cannot be absorbed and so are excreted. Consequently, more cholesterol is excreted via the faeces.
Over 50 published high quality clinical trials have clearly demonstrated the effects of plant stanols and sterols on cholesterol. In particular, one meta-analysis of 41 studies6 showed that taking a 2g-per-day dosage of plant stanols and sterols reduced LDL-cholesterol by a clinically significant 10% 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%, compared with a reduction of only 7.7% in the control group of statin users.
Similarly, a study of plant sterols showed that after 4 weeks on a statin combined with 2g plant sterol-enriched margarine the reduction in low-density lipoprotein cholesterol offered LDL cholesterol reduction equivalent to doubling the dose of statin.10
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.11 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 stanols (found in the Benecol® range of foods) such as margarines and dairy products or sterols (e.g. Flora Pro.activ®, MiniCol cheese®). Alternatively 2g can be achieved by drinking one Benecol ‘one a day' yogurt drink, dairy free drink or a Benecol fruit and dairy smoothie or one Flora Pro.activ mini drink or a 250ml glass of Flora Pro.activ milk or eating a 65g portion of MiniCol® cheese.
In additional to the wealth of evidence to show that a healthy and varied diet, including functional foods containing plant stanols and sterols, can play a significant role in lowering cholesterol, healthcare professionals now have the added confidence from research trials to suggest these foods to their patients as an additional tool in the fight against CHD. However, many products are at a premium cost which should be weighed up before making recommendations to those on a low income.
A disease risk reduction claim relating to plant stanol esters and plant sterols was amongst the first claims to be authorised by the new Health Claims Regulation of the European Commission, which requires all food manufacturers to substantiate their health claims. The announcement of the disease risk reduction claim on 22 October 2009 means that consumers with raised cholesterol levels can feel secure in the knowledge that 2g of plant stanol esters or plant sterols consumed on a daily basis will lower cholesterol levels. High cholesterol is a risk factor in the development of CHD.
In light of the significant results from studies conducted to date, the National Institute for Clinical Excellence (NICE) has also highlighted a research need to establish the effectiveness of plant stanols and sterols, recognising the potential of these products and an appropriately adapted low-fat diet, to avoid the need to use drugs to modify cholesterol levels.
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.
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10. Simons LA (2002) Additive effect of plant sterol-ester margarine and cerivastatin in lowering low-density lipoprotein cholesterol in primary hypercholesterolemia Am J Cardiol. 2002 Oct 1;90(7):737-40.
11. 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.