Is there a difference between olive and corn oil?

Dear Three-in-one,

There's a bit of debate as to which oil to drizzle over your food. Common cooking oils, including corn, olive, safflower, and peanut oils are made up of mostly unsaturated (mono- and polyunsaturated, to be exact) fats, which are often described as “healthy fats.” Research suggests that these two types of fat may help lower cholesterol, normalize blood clotting, improve insulin and blood sugar levels, and decrease the risk of type 2 diabetes. Another fatty acid you may have heard of is omega-3, which is also found in corn and olive oil and have a number of health benefits. Olive oil has been widely regarded as the "healthiest", but some newer research suggests that when included in a well-balanced diet, corn oil may have comparable or possibly greater health benefits than olive oil. These plant-based fats are recommended over animal fats (such as butter or lard) for cooking, but nevertheless they’re still high in calorie content and consuming them in moderation is recommended.

As mentioned, these “healthy fats” are tied to a host of benefits. For quite some time monounsaturated fats were credited with lessening the hardening of arterial walls and thus reducing risks of heart and kidney disease. However, recent clinical studies show that polyunsaturated fats may better protect against heart disease. In addition to promoting heart health, monounsaturated fats and omega-3 fatty acids (which both contain vitamin E and selenium) help control blood pressure, lower low density lipoprotein (LDL) cholesterol, and reduce inflammation in the body.

So how do olive oil and corn oil measure up? Olive oil has a higher percentage of polyunsaturated fats and higher amount of omega-3 fatty acids when compared to corn oil. Corn oil, on the other hand, has higher amounts of omega-6 fatty acids, which increase inflammation, insulin resistance, and the development of white fat tissue. In terms of cholesterol, both corn and olive oil contain no cholesterol; in fact, they both help lower LDL cholesterol in the body. While olive oil has been considered the “healthiest” oil, recent research shows that corn oil is more effective and faster at reducing LDL cholesterol. Corn oil also contains compounds called phytosterols, which help your body reduce cholesterol absorption. 

When it comes to oils, how you use and store it is just as critical as the type you use. Corn oil tends to be more stable at higher heats, whereas olive oil may become rancid and lose its nutrients at high heats, thus diminishing its benefits. Depending on if the recipe calls for high heat or not, one oil may be more suitable on the stove than the other. In terms of storage, olive oil has the most nutritional value when it’s freshest. As soon as it’s exposed to air and light, it begins to degrade and lose its heart-healthy benefits (even if you can’t tell that it’s gone bad). You may be used to checking expiration dates on bottles and cans — olive oil often has both an expiration date and a harvest date. Olive oil enthusiasts and experts suggest checking these dates and using the oil within about six months of harvest, if possible. If you’re into imported olive oil, this rule of thumb may be impacted by transport times and storage conditions, which may impact its freshness. When you store olive oil between uses, try to keep it in a cool environment away from light. Similarly, after opening, try to keep corn oil stored in a cool, dark environment, and to prevent further degradation, it can be stored in a refrigerator.

When shopping for corn oil, some consumers may be concerned with finding ones that are free of genetically modified organisms (or GMO-free). While there is no “official” stance on GMOs, they remain controversial due to their biological and environmental costs and benefits. If a food is genetically modified, companies are not legally obligated label it as such in the United States (U.S.). So, if you'd prefer to stay aware of GMOs, it may be helpful to note that corn is one of the most genetically modified crops, which may make it more difficult to find GMO-free corn oil.

While the existing research on olive and corn oil has certainly shaped the nutritional recommendations you may have heard, it’s also worth noting that even clinical studies have limitations. It’s possible that what's known about olive oil and corn oil today may evolve with new research and deeper understandings of how these oils play a role in people's bodies and health. Another point to consider other than the type of oil itself, is what you’re sautéing, dressing, or marinating. Eating a well-balanced diet in addition to choosing dishes and snacks with healthy fats may make a bigger impact on overall health. Some research suggests that diets with an emphasis on vegetables, fruits, legumes, and whole grains (and less emphasis on meat, poultry, and dairy) when partnered with healthier fats from sources like nuts, corn oil, and olive oil can promote heart health and lower cholesterol. If you’re looking for more individualized advice on diet and nutrition, you may try speaking with a registered dietician or a health care provider.

Here’s to good eating and good health!