Health News

Best Heart Benefits From Canola and Fish Oils -- Not Olive Oil

March 14, 2000 (Atlanta) -- Olive oil may be nearly as dangerous as saturated fat in clogging arteries, according to authors of a study comparing the effects of canola, olive, and fish oils. They presented their findings today at the American College of Cardiology meeting in Anaheim, Calif.

"We expected there to be no detrimental effects at all because they were all good oils. What we found is that two were good and one was not -- olive oil. Olive oil impaired vascular function just like a Big Mac or fries or Sara Lee cheesecake," says Robert Vogel, MD, head of cardiology at the University of Maryland in Baltimore. He tells WebMD that the study's results "represent a major change in terms of what we should be telling people about what they should eat."

Vogel has long been recognized for his work regarding diet and health. "There is such confusion in the population as far as what's good and what's bad," he says. His research specifically focuses on the endothelium, which is the lining of blood vessels such as arteries and veins. When the endothelium is injured, it triggers atherosclerosis, which is the buildup of fatty substances on the blood vessel's walls that leads to heart disease.

His study is based on the famous Lyon Diet Heart Study, published in 1999, which showed that the low incidence of heart disease of coastal Mediterranean residents was due to a "Mediterranean diet" of bread, vegetables and fish, less meat (red meat replaced by poultry), fruit, and -- not olive oil -- but canola oil.

"Most people don't realize that the Lyon diet did not use olive oil. Volunteers in the study didn't particularly like the taste of olive oil, so they substituted with canola oil," says Vogel. "It's fascinating. ... Although they may have made part of their decision based on the tastes of the volunteers, it was actually a very smart thing to do."

In his study, Vogel and colleagues compared olive oil -- which is very much a part of a traditional Mediterranean diet -- with canola and fish oil. Ten volunteers, all with normal cholesterol levels, were given three meals composed of canola oil and bread, olive oil and bread, or salmon, with each meal totaling 50 g of fat.

Both before and after the meals, arterial blood flow in each volunteer's arm was measured using a technique that combines ultrasound and a blood pressure cuff. "We can watch what happens to the size of the artery when we increase blood flow. Normally, the artery should increase 10-15% in diameter. If it doesn't increase, you don't have normal [blood flow]," he tells WebMD. Arterial blood flow can be an indicator of whether the lining of the arteries -- the endothelium -- has been damaged, Vogel says.