Wiseman SA. Mathot JN. de Fouw NJ. Tijburg LB.
Unilever Research Laboratory, Vlaardingen, The Netherlands.
Dietary non-tocopherol antioxidants present in extra virgin olive oil
increase the resistance of low density lipoproteins to oxidation in rabbits.
Atherosclerosis. 120(1-2):15-23, 1996 Feb.
Consumption of a range of dietary antioxidants may be beneficial in
protecting low density lipoprotein (LDL) against oxidative
modification, as studies have demonstrated that antioxidants other than
vitamin E may also function against oxidation of LDL in
vitro. In the present study, the effect of polyphenol antioxidants on the
susceptibility of LDL to copper-mediated oxidation was
investigated after feeding semi-purified diets to 3 groups of New Zealand
white (NZW) rabbits. All diets comprised 40% energy as fat with 17% energy as
oleic acid. Dietary fatty acid compositions were identical. Oils with
different polyphenol contents were used to provide the dietary source of
oleic acid-refined olive oil, extra virgin olive oil and Trisun high oleic
sunflower seed oil. Polyphenolic compounds (hydroxytyrosol and p-tyrosol)
could only be detected in the extra virgin olive oil. Vitamin E was equalised
in all diets. LDL oxidizability in vitro
was determined by continuously monitoring the copper-induced formation of
conjugated dienes after 6 weeks of experimental diet feeding. The lag phase
before demonstrable oxidation occurred was significantly increased in the
high polyphenol, extra virgin olive oil group (P < 0.05) when compared with
combined results from the low polyphenol group (refined olive oil and
Trisun), even though the LDL vitamin E concentration in the
high polyphenol group was significantly lower. The rate of conjugated diene
formation was not influenced by the presence of dietary polyphenols. Results
demonstrate that antioxidants, possibly phenolic compounds which are present
only in extra virgin olive oil, may contribute to the endogenous antioxidant
capacity of LDL, resulting in an increased resistance to
oxidation as determined in vitro.
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