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Sterols, stanols and cholesterol

Systematic review
Results
Comment

Bandolier 64 examined a randomised trial that examined the effects of plant stanols on cholesterol, and found that they were beneficial. But that study was just the one, and with a limited number (100) of subjects. Now we have a systematic review that confirms and extends the results [1].


Plant stanols and sterols have a structure that is very similar to that of cholesterol, and the difference between stanols and sterols is that the former are saturated and the latter are not. Sterols have functions in plants similar to that of cholesterol in animals. Foods enriched with stanols or sterols lower serum cholesterol levels by reducing intestinal absorption of cholesterol.


Stanols and sterols are now found in a variety of margarines and other food products, usually as esters which are hydrolysed in the upper small bowel. They displace cholesterol in absorption processes, though the methods are still speculative.


Systematic review


Randomised trials that tested foods containing stanols or sterols were found from a previous meta-analysis [2] and review articles, and by questioning experts participating in a specialist workshop.


Results


There were 41 trials, almost all of which used esterified stanols or sterols. Most used margarine, and most used placebo margarines or food to ensure double blinding. Mean LDL cholesterol in placebo across all trials was 3.6 mmol/L at 45-54 years and 4.2 mmol/L at 55-64 years.


Stanols or sterols reduced LDL cholesterol by about 10% at all ages (Figure 1). Higher doses gave a larger percentage reduction in LDL cholesterol (Figure 2).



Figure 1: Percentage reduction in LDL cholesterol by plant sterols or stanols according to age of patients (number of trials)




Figure 2: Percentage reduction in LDL cholesterol by plant sterols or stanols according to grams per day of unesterified sterol or stanol (number of trials)





Studies of the use of stanols and sterols in addition to diet or cholesterol lowering agents like statins tended to show an additive effect. A review of safety in human and animal studies showed no adverse effects.


Comment


The two meta-analyses confirm that stanols and sterols taken at about two grams per day will reduce LDL cholesterol by about 10%, or about 0.3 to 0.5 mmol/L in adults. There is a cost, estimated at about £70 a year because stanols or sterol margarines are more expensive than traditional margarines. But there is also a benefit. The calculation is that this reduction in cholesterol should reduce the risk of heart disease by a quarter [2].


References:

  1. MB Katan et al. Efficacy and safety of plant stanols and sterols in the management of blood cholesterol levels. Mayo Clinic Proceedings 2003 78: 965-978.
  2. M Law. Plant sterol and stanols margarines and health. BMJ 2000 320: 861-864.

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