Extra-virgin olive oil improves HDL lipid fraction but not HDL-mediated cholesterol efflux capacity: a double-blind, randomized, controlled, cross-over study (OLIVAUS).

Olive oil (OO) polyphenols have been shown to improve high density lipoprotein (HDL) anti-atherogenic function, thus demonstrating beneficial effects against cardiovascular risk factors. The aim of the present study was to investigate the effect of extra-virgin high polyphenol olive oil (HPOO) vs. low polyphenol olive oil (LPOO) on the capacity of HDL to promote cholesterol efflux in healthy adults. In a double blind, randomized cross-over trial, 50 participants (aged 38.5±13.9 years, 66% females) were supplemented with a daily dose (60 mL) of HPOO (320 mg/kg polyphenols) or LPOO (86 mg/kg polyphenols) for 3-weeks. Following a 2-week wash-out period, participants crossed-over to the alternate treatment. Serum HDL cholesterol efflux capacity, circulating lipids (i.e., total cholesterol (TC), triglycerides (TG), HDL, low density lipoprotein (LDL)) and anthropometrics were measured at baseline and follow-up. No significant between-group differences were observed. Furthermore, no significant changes in HDL cholesterol efflux were found within either the LPOO and HPOO treatment arms; mean changes were 0.54% (95% CI -0.29 to 1.37) and 0.10% (95% CI -0.74 to 0.94), respectively. Serum HDL increased significantly after LPOO and HPOO intake, by 0.13 mmol/L (95% CI 0.04 to 0.22) and 0.10 mmol/L (95% CI 0.02 to 0.19), respectively. A small but significant increase in LDL of 0.14 mmol/L (95% CI 0.001 to 0.28) was observed following the HPOO intervention. Our results suggest that additional research is warranted to further understand the effect of OO with different phenolic content on mechanisms of cholesterol efflux via different pathways in multi-ethnic populations with diverse diets.