EFFECT OF DIETARY OLIVE OIL NON-GLYCERIDE FRACTION ON PLASMA-CHOLESTEROL LEVEL AND LIVER PHOSPHOLIPID FATTY-ACID COMPOSITION

Evidence has shown that dietary supplementation with virgin olive oil (OLO) lowers plasma cholesterol (CH) level. The present study demonstrated in animals that OLO supplementation also suppresses the conversion of 20:3n-6 to 20:4n-6 (DELTA-5 desaturation, or D5D). Our results also indicated that the components in OLO responsible for suppressing both plasma CH and D5D activity are contained mainly in the non-glyceride fraction. Among various components examined, squalene or polyphenolic acids (caffeic, vanillic and protocatechuic acids) failed to affect either plasma CH level or D5D activity. Feeding of polyphenol-stripped OLO did not change plasma CH levels, but it enhanced the D5D activity suggesting that polyphenols might be responsible for suppressing the D5D activity. Previous reports by others have already shown that dietary phytosterols lower plasma CH level whereas they enhance the D5D activity. It is suggested that the hypocholesterolemic and the D5D suppressing effects are two independent functions modulated by different components in the virgin OLO.