Comparison of rice bran oil margarine with Flora margarine and Flora pro-activ margarine for lowering cholesterol : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Human Nutrition at Massey University, Turitea Campus, Palmerston North, New Zealand
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2008
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Massey University
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Abstract
Phytosterols have been shown to be effective in reducing serum cholesterol
levels in numerous human clinical studies and regular consumption is
recommended as part of therapeutic lifestyle changes aimed at reducing low
density lipoprotein (LDL-C) in the treatment of hyperlipidaemia, a risk factor for
cardiovascular disease. Fat based spreads have been shown to be a very successful
vehicle for delivery of plant sterols, readily accepted by consumers and efficacious
in reducing cholesterol levels. Alfa One™ Rice Bran Oil (RBO) spread is a new
product entering into the market place. It is derived from rice bran oil and contains
high levels of unsaponifiable material rich in phytosterols, triterpene alcohols,
ferulic acid esters ([gamma]-oryzanol) and vitamin E isomers. As such it may have the
potential to lower serum cholesterol levels when consumed on a daily basis.
In order to establish the effectiveness of Alfa One™ Rice Bran Oil (RBO)
spread compared with Flora pro-activ® margarine, a well established brand of
plant sterol margarine already proven to lower cholesterol, a randomised double
blind cross-over human clinical trial over 12 weeks was conducted. The study was
divided into two treatment arms. The first arm of the study was to determine
whether Alfa One™ RBO spread (containing 1.5% plant sterols) could lower total
and LDL cholesterol levels to a greater extent than standard Flora margarine
(containing no plant sterols) or Flora Pro-activ® margarine (containing 8% plant
sterols). The second study arm tested the proposition that daily consumption of
Alfa One™ Rice Bran Oil (RBO) spread in conjunction with rice bran oil
(containing 0.5% plant sterols) would lower total and LDL cholesterol to a greater
extent than Alfa One™ RBO spread in isolation and more than Flora margarine in
conjunction with sunflower oil.
Eighty mildly hypercholesterolaemic individuals (total cholesterol [greater than or equal to] 5 mmol/L and [less than or equal to] 7.5 mmol/L) were recruited and randomised into two groups of
forty. Participants were asked to continue with their normal dietary pattern but to
replace any margarine/butter/fat consumption with the trial products. One group of
40 were then assigned to the first treatment arm of the study (margarine-only
group) and were randomised to consume 20 g (4 teaspoons) Alfa One™ RBO
spread daily for 4 weeks, or 20 g Flora margarine daily for 4 weeks, or 20 Flora
pro-activ® daily for 4 weeks. Phytosterol levels delivered in these amounts were:
RBO margarine: 118mg phytosterol and 14 mg [gamma]-oryzanol; Flora proactiv®
1600 mg phytosterol; Flora margarine 0mg phytosterol. The second group of 40
were allocated to the second arm of the trial (margarine and oil group) and
consumed 20 g Alfa One™ RBO spread and 30 ml rice bran oil (RBO) daily for
4 weeks, or 20 g Flora margarine and 30 ml sunflower oil daily for 4 weeks, or
20 g Alfa One™ RBO spread daily for 4 weeks, changing treatment at the end of
each 4-week period. Phytosterol amounts delivered in these amounts were: RBO
margarine: 118 mg phytosterol and 14 mg [gamma] oryzanol; RBO 222mg mg
phytosterol, 150 mg [gamma] oryzanol. Each participant consumed all three treatments in
a random order over a 12 week period. At baseline and following each 4 week
intervention period, measurements were made of weight and blood pressure.
Venous blood samples were collected for analysis of total cholesterol, low density
lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C),
total cholesterol: HDL-C, triglycerides and plasma phytosterols. Three-day diet
records from each individual were also collected for analysis of normal dietary
intake.
Results showed that compared to a standard Flora margarine, Alfa One™
RBO spread significantly reduced total cholesterol by 2.2% (P=0.045), total
cholesterol:HDL by 4.1% (P=0.005) and LDL-C by 3.5% (P=0.016), but was not
as effective overall as Flora Pro-activ® which reduced total cholesterol by 4.4%
(P=0.001), total cholesterol:HDL by 3.4% (P=0.014) and LDL-C by 5.6%
(P=0.001). Consumption of Flora margarine alone produced no significant
decrease from baseline figures in any of the cholesterol parameters measured.
Surprisingly, in group two, the addition of rice bran oil to the Alfa One™ RBO
spread produced no differences in cholesterol levels. The reason for this
unexpected result is being explored further.
These results confirm that Alfa One™ RBO spread is effective in lowering
serum cholesterol levels when consumed as part of a normal diet. Studies have
shown that a 1% reduction in LDL-C can equate to a 2% decrease in coronary
heart disease (CHD) risk thus suggesting that the 3.5% reduction demonstrated by
Alfa One™ RBO spread in this study could be effective in reducing CHD risk as
much as 6% in a mildly hypercholesterolaemic population.
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Keywords
Human nutrition, Rice bran oil margarine, Flora margarine, Flora pro-activ margarine, Phytosterols, Plant sterols, Reduction of serum cholesterol