Should You Switch to Corn Oil to Lower Cholesterol?
A newly published study shows that corn oil reduces cholesterol much more effectively than extra virgin olive oil. But before you make a switch, there are some other factors to consider.
Monica Reinagel, MS, LD/N, CNS
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Should You Switch to Corn Oil to Lower Cholesterol?
Cindy writes,
“Recently I’ve been seeing ads on television saying that corn oil is better than olive oil for lowering cholesterol. I’ve always used olive oil and canola oil. Now, I’m thinking of changing from canola oil to corn oil. Should I make the switch?”
I bet Cindy’s not the only one who has been seeing these ads. Makers of corn oil are spending a lot of money right now to promote the results of a study showing that a diet rich in corn oil reduced cholesterol more than a diet rich in olive oil.
Those of you with a very good memory might remember me writing about this same study a few years ago, when the unpublished results were first presented at a scientific meeting. This month, the study was finally published in a in a peer-reviewed journal. Because it’s getting a lot of new attention, I thought it would be worth revisiting.
First, let’s take a closer look at what the study found and then I’ll tell you whether I think it makes sense to start using corn oil in place of other oils you might be using.
How Corn Oil Affects Cholesterol
In the study, healthy adults consumed either 4 Tablespoons of corn oil or 4 Tablespoons of extra virgin olive oil per day for three weeks. The oils were incorporated into various foods, including muffins and yogurt. After three weeks on the corn oil diet, the subjects saw a 9% reduction on average in their LDL cholesterol versus just 2% for the olive oil diet.
Although this finding might surprise you, it was not a surprise to the researchers. Corn oil is naturally rich in phytosterols, compounds that are shaped very similarly to cholesterol and can block the absorption of cholesterol from foods. Basically, the phytosterols occupy the cellular parking spots that cholesterol molecules would normally pull into. Because those spots have already been taken, the cholesterol ends up passing through the system without finding a place to park. Result: less cholesterol is absorbed.
Because corn oil contains a lot more phytosterols than olive oil, it is not surprising that it blocks cholesterol absorption a lot more effectively. Nonetheless, I’m not convinced that you should replace your olive oil (or your canola oil) with corn oil.
The Problem with Corn Oil
Despite its beneficial effect on cholesterol absorption, there are two potential concerns with adding corn oil to your diet. One is that corn oil is high in polyunsaturated fat—a type of fat that can produce harmful compounds called HNEs when heated. Even if you’re not heating them, polyunsaturated fats are easily oxidized, causing the oils to become rancid.
Monounsaturated fats, on the other hand, are more stable when heated and less prone to oxidation and rancidity. Because olive oil and canola oil are higher in monounsaturated fats and lower in polyunsaturated fats, they seem (to me, anyway) like a better choice.
See also episode # 124: Which oils are best for cooking
The other concern with corn oil is that it is high in omega-6 fats. Now, there’s nothing wrong with omega-6 fats, per se. In fact, they are considered essential to our diets. However, it is possible to get too much of a good thing. If our diets are too high in omega-6, it keeps the equally important omega-3s from doing their good work.
It’s a little like phytosterols and cholesterol competing for the same cellular parking spot. Only in this case, the problem is that omega-6 and omega-3 are competing for the same enzymatic pathways. If you have similar amounts of omega-6 and omega-3 in your diet, there’s plenty of room along the enzymatic freeway for both to make their way. But if too many omega-6 fats are hogging all the lanes on the enzymatic freeway, the omega-3s cannot get to work on time—or ever.
Avoiding oils that are high in omega-6, such as corn oil, is one of the best ways to maintain a balance between omega-6 and omega-3 fats, which gives omega-3s a fighting chance of reaching their cellular destinations. Olive oil and canola oil are both much lower in omega-6 than corn oil. And as a bonus, canola is relatively high in omega-3s.
See also: Episode # 85 Fish Oil and Omega-3s and #185 on Does the Ratio of Omega-6 Matter?
How to Get More Phytosterols
Finally, the cholesterol-reducing action of corn oil appears to be mostly due to its phytosterol content. But corn oil is not the only way to get more phytosterols into your diet. In fact, guess which oil contains almost as much phytosterols as corn oil?
Canola oil.
And that’s why I don’t think it makes sense to replace your canola or your olive oil with corn oil.
Although olive oil is not particularly rich in phytosterols, it does have the virtue of being extremely low in both polyunsaturated fats and omega-6s. Extra virgin olive oil also contains polyphenols that may benefit your heart in other ways. Plus, It’s delicious.
You may not wish to use olive oil exclusively, however.I also like to have a less expensive and more neutrally-flavored oil on hand.
Canola and corn oil contain similar amounts of phytosterols, but canola is lower in polyunsaturated fats, meaning it is more stable at high heat and resistant to oxidation at room temperature. It’s also lower in omega-6 and higher omega-3. That’s why canola gets the number 2 spot in my cupboard and not corn oil.
There are lots of other healthy foods that provide phytosterols, as well: Peanuts, pistachios, wheat germ, wheat bran, are particularly good sources, but phytosterols are found in a wide variety of fruits, vegetables, grains, legumes, and nuts. Below, you’ll see the amount of phytosterols in various foods. If you wanted to get the amount included in this study, your goal would be 400-500 mg/day. Bon appetit!
About the Author
Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes’ most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation’s leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.