Plant sterol and stanol margarines and health

Law presented a case for the introduction of plant sterol and stanol
containing margarines into the food chain for the primary prevention of
heart disease (1). There are however a number of concerns about such a
policy.

Phytosterolaemia, a very rare homozygous recessively inherited defect, is
characterised by increased absorption of plant sterols and accelerated
atherosclerosis, and it remains to be shown whether heterozygous carriers,
found with a greater frequency, are predisposed to accumulate these
compounds (2). As has been shown in many other human studies, a recent
study on cholesterol reduction by different plant stanol mixtures in
postmenopausal women (3) found a four-fold increase in serum campostanol
with the use of campostanol ester-rich margarine and a two-fold increase
in serum sitostanol with sitostanol ester-rich margarine. The serum
cholesterol precursor sterols were similarly increased by +12% to +19%
with stanol-ester containing margarine or butter. Although these
increases were considered to be meaningless, since other plant sterol
levels were decreased, it is possible that in some populations long term
increases in blood plant stanol or sterol levels may promote
atherosclerosis.

Law's paper suggests that people in their fifties would achieve a 0.5
mmol/l reduction in LDL cholesterol when consuming two or more grams of
plant sterol or stanol per day and that this would reduce the risk of
heart disease by about 25% after two years (1). Such a 0.5 mmol/l
reduction in LDL cholesterol is equivalent to a 0.6 mmol/l or 10%
reduction in total cholesterol. As a 1.5% coronary risk reduction per 1%
total cholesterol fall is regarded as realistic, a 10% cholesterol
reduction translates to a 15% reduction in major coronary events. In
controlled studies dietary change can reduce total cholesterol by 10 to
15%, but in free-living subjects less than half this reduction is
achieved. Hence it is likely that cholesterol lowering margarine, when
used by the general population, will achieve only an average 5% reduction
in total cholesterol with a large variability due to differences in
compliance and genetic heterogeneity.

A review (4) of cholesterol lowering margarines following the marketing of
two such products in the USA, concludes that the long term effect of these
products on mortality and morbidity from coronary artery disease is
currently unknown, and that the benefits of cholesterol lowering may be
offset by increased plasma plant sterol concentrations and reduced plasma
antioxidants such as beta-carotene (2).

The American Heart Association is also cautious (5): Alice Lichtenstein
warns that no studies have shown prophylactic effects and that these
additional ways of lowering cholesterol have small effects and should not
give people a false sense of security. Basic diet and lifestyle changes,
as has been recommended for years, rather than one easy change, is
advised.

In conclusion, I believe that there is not yet a good evidence base for
recommending the widespread use in the general population of cholesterol
lowering margarines in the prevention of coronary heart disease.

Charles van Heyningen

Consultant Chemical Pathologist

University Hospital Aintree

References:

(1) Law M.R. Plant sterol and stanol margarines and health. BMJ 2000,
320, 861-864.

(2) Thompson G. R. Plant lipids that lower serum cholesterol. Eur.
Heart J. 1999, 20, 1527-1529.

(3) Gylling H, Miettinen TA, Cholesterol reduction by different plant
stanol mixtures and with variable fat intake. Metabolism 1999, 48(5), 575
-580.

(4) The Medical Letter 1999, 41(1055), 56-58.

(5) Larkin M, Functional foods nibble away at serum cholesterol
concentrations. Lancet 2000, 355, 555.