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Say No to Olive Oil?
May 19, 2000 -- Could olive oil -- long considered the healthiest fat around -- be as bad for us as cheeseburgers or creamy desserts?
That's the jaw-dropping conclusion of University of Maryland heart specialist Robert Vogel, MD. At the March meeting of the American College of Cardiology, he stunned the nutrition world by warning that olive oil could be as dangerous to your heart and arteries as a Big Mac or a giant piece of cheesecake. "If you've been using olive oil because you think it's healthy," says Vogel, "it's time to think again."
Olive Oil? Bad for Your Heart?
Unfortunately, we've grown used to this kind of dietary flip-flop. Many Americans have begun to wonder if even the experts know what they're talking about. One day margarine is good for you, the next it's bad. One day vitamin E protects against heart disease, the next it offers no benefit at all. Now it's olive oil's turn.
Vogel tested the effects of three different meals on a group of 10 volunteers who had normal cholesterol levels. One meal consisted of canola oil and bread. Another was olive oil and bread. The third meal was a piece of salmon. All three meals contained 50 grams of fat.
But their effect on blood vessels was very different. Before and again three hours after each meal, Vogel's team measured constriction of the volunteers' arteries. Sharp constriction can injure the inner lining of blood vessels, according to Vogel.
The arteries didn't constrict much after the salmon meal. After the meal containing canola oil, they constricted slightly, reducing blood flow by 11%. After the olive oil and bread combination, however, blood flow plummeted 34% -- exactly the effect that Vogel had seen in previous research after volunteers ate a Big Mac with fries.
The Hidden Culprit
Vogel believes the culprits in olive oil are the omega-9 fatty acids that make up most of the oil. These fatty acids seem to cause blood vessels to constrict. Omega-3 fatty acids, in contrast -- the same kind found in fish oil, and the ones added to canola oil -- don't appear to have this effect. What's that got to do with heart disease? "When blood vessels constrict, their lining, called the endothelium, may be injured," says Vogel. "Repeated injuries can add up to a higher risk of coronary heart disease." What's more, in people with diabetes, which typically causes damage to blood vessel linings, the effect of olive oil could worsen an already dangerous condition, Vogel says.
Worrisome? Maybe. But don't toss out that high-priced bottle of extra-virgin oil just yet. Dozens of other investigations, after all, have found important health benefits associated with olive oil. And though this latest finding is provocative, it's still just one study -- and a very small one at that.
"We're talking about an isolated biological effect, the constriction of blood vessels. But as yet there's no solid evidence that this has any direct meaning as far as heart disease goes," says Frank Sacks, MD, a cardiologist and researcher at Harvard Medical School. "It certainly hasn't been established as a risk factor, like elevated cholesterol or high blood pressure."
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