Warning: This oil comes with potentially damaging side effects due to either the ingredient it's made from or the manufacturing process used to extract it. Because these negative effects overshadow the potential benefits, I do not recommend this oil as a food or for therapeutic use. Always be aware of the potential side effects of any herbal oil before using.
Food nutrients are highly sensitive to heat,1,2 so there are several factors to consider when cooking to preserve as much of these nutrients as possible. One of these factors is the cooking oil you use.
Some cooking oils are stable enough to resist chemical changes when heated to high temperatures, while other oils, like polyunsaturated vegetable oils, can increase the risk for heat-induced damage and create high-energy molecules called free radicals upon degrading inside your body.3,4 One of the most popular vegetable oils is corn oil. Discover the health risks of using corn oil for cooking and whether this oil is good for any other purpose.
What is corn oil?
Corn or maize oil is extracted from the germ of corn. It’s mainly used for cooking and is also a key ingredient in margarine and other processed foods.5 Corn oil is also used in various industrial applications, such as stock for biodiesel6 and a constituent in the production of resins, plastics and lubricants, to name a few.7
Despite being generally less expensive than other vegetable oils on the store shelf,8 a huge factor in its price is the staggering amount of subsidies the United States gives to corn to underwrite the cost. Corn is one of the most heavily subsidized crops in the country, raking in over $111.2 billion from the government between 1995 and 2017, according to data from the Environmental Working Group (EWG).9
As you can see, this subsidy on a basically unhealthy food easily undersells healthy choices. A study published in the Journal of the American Medical Association shows that the high consumption of foods derived from subsidized commodities like corn is associated with an increased risk of cardiometabolic disease in adults.10
Moreover, the problem with using corn oil and other vegetable oils for cooking is that they contain perishable bonds that create free radicals in the presence of oxygen, a process also known as autoxidation.11 These free radicals can lead to cholesterol oxidation, which has been linked to an increased risk of diseases such as atherosclerosis, Alzheimer’s disease, retinal degeneration, age-related macular degeneration and cataracts.12
Corn oil also contains very high amounts of omega-6 fats, which can throw your body’s omega-6 to omega-3 ratio out of balance. Corn oil is reported to have an omega-6 to omega-3 ratio of 46-to-113 — a far cry from the ideal 1-to-1 ratio. The standard American diet already has far too much omega-6 in it, and the serious distortion of the ratio further increases your risk for many degenerative diseases.14
Uses of corn oil
Apart from serving as a less-than-ideal cooking oil, corn oil is used in manufacturing paint, ink, textiles and insecticides.15 It also sometimes functions as a carrier oil for drug molecules in pharmaceutical products.16
Corn oil is used for skin care products as well, including soaps, balms and other bathing essentials.17 You can also massage it onto your scalp to help strengthen and add shine to your dry hair.18 Here are some of the ways you can use corn oil around your home:
- Lubricate a key lock — If you have a sticky key lock at home, wipe the key with corn oil before inserting it into the lock. The oil acts as a lubricant, making it easier for you to turn and pull out the key.19
- Clean up watermarks from wooden furniture — Mix equal parts of salt and corn oil then rub it onto the watermarks on your wood furniture. Use a clean cloth to polish it off.20
- Coat your snow shovel — Rubbing the oil on your shovel will prevent snow from sticking to it.21
Composition of corn oil
According to the United States Department of Agriculture, industrial and retail corn oil contains 27.5 grams of total monounsaturated fats, 54.6 grams of total polyunsaturated fats and 12.9 grams of total saturated fats per 100-gram serving.22
One important caveat you need to consider regarding this oil is that it’s typically derived from genetically modified (GM) seeds that are designed to resist herbicides like glyphosate.
A study published in the International Journal of Biological Sciences demonstrates the toxicity of three GM corn varieties from biotech company Monsanto, now Bayer. Results show that consuming GM corn increases the risk for hepatorenal toxicity and unintended direct or indirect metabolic consequences.23
How corn oil is made
To extract corn oil from the corn germ, a combination of continuous screw presses and solvent extraction is used. The initial expeller extracts around 50% of the oil content, while the solvent extraction brings the total yield to 95%. The corn oil is then refined through degumming to remove phosphatides, alkali treatment to neutralize free fatty acids and bleaching to remove trace elements and create a desirable color.
The final steps of the refining process include winterization, a process wherein high melting waxes are removed, and deodorization.24 This entire process may contribute to the potential health risks of corn oil.25
How does corn oil work?
When used for cooking, corn oil serves as a medium in which heat can be transferred. It may also help contribute to the flavor and texture of food.26 However, I do not recommend using corn oil for cooking, as it can potentially lead to a variety of health problems. For practical uses, such as for aromatherapy, skin conditioning or hot oil massage, corn oil works as a carrier oil.27
Is corn oil safe?
Corn oil and other polyunsaturated vegetable oils are heavily marketed for "healthful" cooking alongside the vilification of saturated fats, which actually do not cause heart disease and, on the contrary, serve as a healthful addition in your diet.28 Aside from the oxidized oil dangers I discussed in the first section, here are two other issues you should be aware of with corn oil and vegetables oils:
- The majority of these vegetables oils in the U.S. are made from genetically modified crops,29 which can contain residues of the herbicide glyphosate and Bt toxin found in GM corn and soy.
- They are heavily processed, potentially causing a range of ill health consequences.30
Side effects of corn oil
Some of the worst foods you can consume are those cooked with polyunsaturated vegetable oils like corn oil.31 The introduction of oxidized cholesterol into your system is a big concern, converting your good cholesterol into bad, which leads directly to cardiovascular diseases.32
When heated, corn oil produces harmful chemicals called aldehydes, which have been found to increase the risk for autism spectrum disorder, Parkinson’s disease and gastric, breast and prostate cancer.33 A study published in the Journal of Lipid Research also shows that polyunsaturated fatty acids promote hepatic inflammation.34
If you’re looking for a cooking oil that is less susceptible to heat-induced damage and will not put you at risk of various chronic diseases, consider using coconut oil. Coconut oil contains healthy fats that may help support your heart health,35 thyroid function,36 immune system,37 brain function38 and metabolism,39 among others.