Sept. 5, 2006 -- All olive oils may not be created equal when it comes to protecting against heart disease.
Virgin olive oil is made from the first pressing of olives and contains higher levels of a class of antioxidants known as polyphenols than more refined olive oils that come from later pressings.
Researchers say these polyphenols may provide another way to reduce the risk of heart disease in addition to the heart-healthy benefits attributed to the monounsaturated fatty acids found in olive oil.
Recent studies have suggested that the bulk of olive oil's heart-healthy benefits comes from good fatty acids (monounsaturated fatty acids), but researchers say polyphenols may also contribute to those benefits and further reduce the risk of heart disease.
Virgin Olive Oil Best for Heart
In the study, published in the Annals of Internal Medicine, researchers compared the effects of consuming olive oils with varying levels of polyphenols on heart disease risk factors in 200 healthy European men.
The men were divided into three groups and ate about 1 tablespoon of either virgin olive oil, refined olive oil, or a mixture of the two, every day for three weeks. Then, after a two-week hiatus, they were retested with one of the other types of olive oil.
Researchers found that the virgin olive oil higher in polyphenols increased the level of good, high-density lipoprotein (HDL) cholesterol more than the other two types of olive oil.
Virgin olive oil also produced another healthy antioxidant effect. It increased the level of substances in the body that prevent the oxidation of bad, low-density lipoprotein (LDL) cholesterol. Oxidation of this type of cholesterol is linked to the formation of clots in blood vessels, which could lead to heart attack or stroke.
Researcher Maria-Isabel Covas, Msc, PhD, of the Municipal Institute for Medical Research in Barcelona, Spain, and colleagues say the results show "olive oil is more than a monounsaturated fat.
"The polyphenol content of an olive oil can account for further benefits on HDL cholesterol levels and oxidative damage, in addition to those from its monounsaturated fatty acid content," they write. "Our study provides evidence to recommend the use of polyphenol-rich olive oil, that is, virgin olive oil, as a source of fat to achieve additional benefits against cardiovascular risk factors."
More studies are needed to examine virgin olive oil versus more refined oil and the risk for developing heart disease.