The Great Olive Oil Misconception Dr. Ornish Responds | Reader's Digest

The Great Olive Oil Misconception — Dr. Ornish Responds

Dr. Ornish answers questions about the health value of canola oil versus olive oil.

By Dean Ornish | MD

In his September column, Dr. Dean Ornish reported that olive oil is not as healthy as everyone thinks it is. A number of readers were dismayed and disbelieving of this news, and others thought canola oil, which Dr. Ornish recommends, is unhealthy. Dr. Ornish addresses these concerns:

First of all, on the health benefits of canola oil versus olive oil: Olive oil, like all oils, is 100% fat. Since fat has 9 calories per gram, whereas protein and carbohydrates have only 4 calories per gram, people consuming a lot of olive oil are also consuming a lot of extra calories.

As I wrote in my column, olive oil “lowers” cholesterol only when substituted in equal amounts for foods that are higher in saturated fat. In other words, if you replace 60 grams of butter with 60 grams of olive oil, your LDL cholesterol level is likely to decrease—not because olive oil lowered your cholesterol level but because it didn’t raise it as much. This is a very common misconception, causing many people to consume a lot of olive oil in the belief that it will somehow magically lower their cholesterol levels.

Studies comparing the effects of canola oil versus olive oil show that canola oil consumption results in lower LDL cholesterol levels. This is not surprising, since olive oil contains approximately 14% saturated fat, whereas canola oil has much less. It’s clear that olive oil is a healthier fat than many others, but not as healthful as canola oil or fish oil.

A study by Dr. Robert Vogel in the Journal of the American College of Cardiology found that olive oil significantly reduces blood flow to different parts of your body, whereas canola oil and salmon do not. This measure of blood flow, called flow-mediated vasodilation (FMD), is a standard, well-accepted test by the American Heart Association and others. In this study, blood flow (FMD) was reduced by 31% after an olive-oil meal but was not reduced by a meal with a similar amount of fat from canola oil or salmon, probably due to the higher content of the protective omega-3 fatty acids in canola oil and salmon.