olive oil phenolics protect LDL

From: Doug Skrecky (oberon@vcn.bc.ca)
Date: Sat May 20 2000 - 11:35:39 MDT

  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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