According to the report, adults who consumed 25 milliliters (mL) or nearly 2 tablespoons of virgin olive oil daily for one week showed less oxidation of LDL ("bad") cholesterol and higher levels of antioxidant compounds, particularly phenols, in the blood.

Antioxidants can help prevent oxidative damage, which is caused by free radicals, byproducts of the body's normal processes that can damage body tissues. Studies have shown that the oxidation of LDL cholesterol is associated with the hardening of arteries that can lead to heart disease.

The findings may help to explain the heart healthy benefits of the Mediterranean diet, which is rich in olive oil, fruits, vegetables and grains and low in saturated fat from meat. Studies have documented lower rates of heart disease in countries such as Italy and Spain, where people consume more than one third of their daily calories from fats high in monounsaturated fatty acids. These fats may help to lower total cholesterol and LDL cholesterol.

But while all types of olive oil are sources of monounsaturated fat, virgin olive oil also contains higher levels of antioxidants, particularly phenols and vitamin E, because it is less processed.

Our results support the idea that daily ingestion of virgin olive oil could protect LDL from oxidation.

Phenols from other sources, such as red wine and onions, have been shown to help control cholesterol but there is little information about the effect of antioxidants from olive oil on cholesterol.

To investigate, the researchers instructed 16 healthy adults to avoid phenol-containing foods such as coffee, tea, wine and vegetables for 4 days. On the fifth day adults consumed 50 mL of virgin olive oil -- about 3.3 tablespoons -- alone or with bread.

The participants avoided all other foods with phenols for the next 24 hours and then ate their regular diet, supplemented by 25 mL of olive oil daily, for a week. Study volunteers were also told to avoid high-fat foods such as butter, margarine, cooking oil, nuts, baked foods and eggs.

Blood samples taken before and during the study revealed higher levels antioxidant compounds, including vitamin E and phenols, after one week. Similarly, levels of oleic acid, the predominant type of fat in olive oil, as well as monounsaturated fatty acids, were higher. These changes were associated with a slower LDL oxidation rate.

In addition to the LDL-lowering effect of virgin olive oil, the results suggest that an intake of 25 mL/day could increase the resistance of LDL to oxidation because it becomes richer in oleic acid and antioxidants. These benefits could be achieved by including virgin olive oil daily in our diet.

European Journal of Clinical Nutrition April 2002;56:114-120

Dr. Mercola's Comments:

Olive oil is clearly one of the good oils. Most of us do quite well with it as it does not upset the critical omega 6:3 ratio and most of the fatty acids in olive oil are actually an omega-9 oil that is monounsaturated. When obtaining olive oil you will want to obtain a high quality extra virgin oil, as olive oil is like other oils and can easily go rancid when exposed to air, light or high temperatures. I much prefer olive oil to the other monounsaturated fat, canola oil for a number of reasons that are outlined in the links below. While it is true that canola oil is a source of ALA (an omega-3 fat), there are better sources such as ground up flax seeds. As I have said previously the ALA in flax is not easily converted by most of us to the higher chain fats, EPA and DHA, which appear to have most of the cardiovascular and cancer protection benefits. Related Articles: Olive Oil May Help Prevent Colon Cancer Beware of Canola Oil Secrets of the Edible Oil Industry Olive Oil, Cooked Vegetables May Reduce Arthritis Risk