Researchers from the University of Barcelona recruited 110 healthy men from Germany, Denmark and Finland -- non-Mediterranean countries -- and 45 Spanish and Italian men, from Mediterranean regions. The researchers believed that the non-Mediterranean men had not regularly consumed olive oil, while the Mediterranean men had.
Both the non-Mediterranean and the Mediterranean men were instructed to include 25 mL per day of one of three similar types of olive oil for the duration of the study, which was comprised of three three-week periods of supplementation separated by two two-week periods without supplementing.
By the study's end, the researchers found that blood levels of oleic acid -- a monounsaturated fatty acid -- were 2 to 3 percent higher in the men from non-Mediterranean countries, while the Mediterranean men's oleic acid levels did not significantly change.
In addition, the non-Mediterranean men's systolic blood pressure levels dropped three percent after olive oil supplementation.
"The results of this study suggest that a moderate consumption of olive oil may be used as an effective tool to reduce SBP (systolic blood pressure) of healthy men to do not typically consume a Mediterranean diet," wrote the researchers, who were led by Isabel Bondia-Pons.
Bondia-Pons and colleagues have called for further research into the effects of dietary modifications on blood pressure, particularly studies of longer duration.