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Ask Tufts Experts May 2018 Issue

Q. My husband and I use a lot of olive oil. Are canola, corn and other plant oils as healthy?

A. ”There’s no definitive evidence right now to show that olive oil is superior to other liquid plant oils,” explains Alicia Romano, MS, RD, LDN, Registered Dietitian, Frances Stern Nutrition Center, Tufts Medical Center.

“One of the differences between oils is in the types of fatty acids in them. You’ve probably heard a lot about the health benefits of omega-3 and omega-6 fatty acids; these are polyunsaturated fatty acids.

“Some research suggests that replacing saturated fats in butter and lard with polyunsaturated fats from plant oils is associated with lower risk of cardiovascular disease. Both soybean oil and corn oil are higher in polyunsaturated fats than olive oil. That said, olive oil—and its mostly monounsaturated fats—is still considered a healthy choice. In fact, there is preliminary evidence that phytochemicals in extra-virgin olive oil may contribute to the reduced cardiovascular risks associated with the Mediterranean diet pattern. If you prefer the taste of olive oil to other options, by all means use it to cook with and dress your salads. Ideally, consume a variety of plant oils, the same way you eat a variety of fruits and vegetables to obtain maximum benefits. But there is an exception: Tropical oils like palm and coconut are high in saturated fats, so oils relatively higher in unsaturated fats are the better choice.”

Comments (2)

Unfortunately, the oils high in polyunsaturated fats that are low in trans fat when fresh gradually become high in trans fat over time, due to spontaneous conversion of cis isomers to trans isomers. By the time you buy a bottle of oil, the trans fat content may be much higher than what the label says. This is less of a problem for olive oil because monounsaturated fats do not have trans isomers.

Posted by: stpeters43 | May 15, 2018 3:45 PM    Report this comment

This comment is doubly inaccurate. Spontaneous conversion is much more unlikely than, for example, the development of rancidity (which you can test with your nose). Conversion typically requires a catalyst to break a double bond and enable the parts of the molecule on each side of the bond to rotate relative to each other, from the cis to the trans configuration. The attachment of the catalyst is reversible, so the double bond can reform in the trans configuration. Monounsaturated fats CAN have trans isomers, but trans isomers are rare naturally, just as they are for polyunsaturated fats. It is the catalysts used to hydrogenate fats that create trans fats, and the fats that are hydrogenated commercially are typically polyunsaturated. If you know of any reputably published study that contradicts anything that I have said, please post the reference.

Posted by: JTaylor | May 15, 2018 7:42 PM    Report this comment

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