Is corn oil healthy? A question asked more and more recently given the growing utilization of corn oil worldwide and the confusion regarding its nutritional value.
According to statistics, the global consumption of vegetable oils increased significantly from 2013 to 2019 to reach approximately 200 million metric tons.
In parallel and as a logical consequence, the global vegetable oil production has experienced a significant growth over the last several years to amount in 2019 approximately 208 million metric tons.
Below, we will focus on corn oil, a widely used vegetable oil that is expected to reach 7180 million US$ by 2024 in the global corn oil market.
Well, let us see the details.
What is corn oil?
Corn oil called also maize oil is an edible oil extracted from corn kernels.
Corn kernels are the fruits of corn called in many places maize. They are considered as grains and consists mainly of three essential constituents: germ, bran and endosperm.
The germ is the small part in the seed that germinates and grows to make a new maize plant. It is, indeed, the richest part of kernel in nutrients and containing 85% of the kernel’s oil.
That is why, the major raw material of corn oil is corn germ. The oil constitutes of half of the germ – the embryo- of the corn kernel (the corn grain).
Corn oil has a light color and texture and a neutral bland taste, which makes it a valued popular vegetable oil on the market, widely used for salads and cooking.
It tends also to have a good flavor stability and a high smoke point, which makes it a great choice for foods frying.
Indeed, every vegetable oil you cook with has a smoke point called also a burning point that ranges relatively between a low temperature 325°F to very high one 520°F.
This smoke point means the temperature at which the oil starts to burn and smoke. Once, the oil is heated past its burning point, smoking is a sign that it is breaking down.
Once the oil breaks down, it means that not only it imparts a burnt and bitter flavor to foods, but also, it becomes more oxidized.
Meaning that the beneficial nutrients contained in the oil, if it is unrefined, are destroyed and free radicals, chemicals that can harm the body and lead to aging and many diseases, are created.
Corn oil has a high smoke point of 450°F (230°C) which make it good for frying.
It is also important to note that the main production areas of corn oil are mainly those of corn as it is produced as a co-product of cornstarch. These global major zones are USA, China, Brazil and the EU.
What is the corn oil Nutritional value?
The caloric ratio of Corn oil is in the top of the caloric ratio pyramid, meaning 100% of fat with no carbs and no proteins. The thing that makes it a good source of essential fatty acids.
Following the USDA, one tablespoon of corn oil –the equivalent of 13,6g – contains:
- 122 Calories
- 13,6 g of total fat
- 0,027 mg of choline
- 1,94 µg of vitamin E (alpha-tocopherol) –the equivalent of 10% of the DV
- 0,258 µg of vitamin k
For the same serving size (1 tbsp.), corn oil total fat structure is made mainly of 14% of saturated fat (1,76g), 29% of monounsaturated fat (3,75g) and a good portion of 57% of polyunsaturated fat (7,44 g).
By detailing more the corn oil fatty acids composition, we notice that it comprises a high level of 53,5% omega-6 fatty acids mainly linoleic acid (18:2), 27% of omega-9 fatty acids mainly oleic acid (18:1) and some percentages less than 1,2% of omega-3 fatty acids mainly α-linolenic acid (18:3).
Therefore, we note that corn oil contains far too much essential omega-6 fatty acids and low percentages of omega-3 fatty acids. The ratio between omega-6 and omega-3 is 46: 1. Meaning 46 omega-6s for every 1 omega-3.
The ratio between omega-6 and omega-3 is the most important number to keep in mind. Essential fatty acids consumption should be in the right quantities to avoid any imbalance that can lead to some chronic diseases.
In other words, the optimal recommended ratio of omega-6 to omega-3 fatty acids in the diet should be 4:1 or less.
How is corn oil produced?
Production of corn oil is made by extracting oil, as mentioned before, from corn germ existing inside the corn kernel.
The germ is separated from the rest of kernel via the operation of milling. In fact, the other parts of the kernel, the endosperm and bran, are generally used to produce other edible solids like corn flour, cornstarch, etc.
There are various methods of extracting corn oil from corn germs: cold pressed method, expeller-pressed method and a combination expeller-solvent process.
Let us describe the steps of each method.
. Expeller-pressed oil:
The oil is extracted via an expeller-press called also screw press. Using an intense friction and pressure, the corn kernels are pressed through a cavity.
During this process of extraction, there is no heat added. Yet, the heat is created around 140°F (60°C) and 210°F (99°C) due to the seeds friction.
After that, the extracted corn oil is removed and the remaining pressed kernels are, generally, used later as animal feed.
It is important to note that this expeller pressing extraction can generate a lot of heat due to the pressure and friction, which can make the oil go rancid.
That is why; to avoid this risk some companies use the next cold pressed method.
. Cold-pressed oil:
Using an oilseed press, the corn kernels are put inside the machine and are crushed in order to obtain the oil.
This method doesn’t need any additional chemicals or heat. Besides, during the process, the temperature of kernels is typically lower than 120 °F (50 °C) compared to the expeller-pressing extraction that can reach higher temperatures.
Cold-press extraction should occur at a temperature of 120°F or less. The thing that makes the moisture of the input corn kernels an important parameter.
So, given this temperature requirements of both cold-press and expeller-pressing methods, these processes of extraction are slow and need a large number of kernels to produce a high yield.
That is why; most manufactures do not use these methods that produce the called “unrefined” or “organic” pure oil.
. Refined oil:
Refined oils are each oil obtained via a complex process combining high temperature and the use of chemicals.
Generally, the refining process of corn oil consists of the following steps.
Corn oil is expeller-pressed, then, the pressed cake is treated by washing it using a solvent in order to extract any residual oil from the pulp.
The solvent used is ordinarily neurotoxin hexane or 2-methylpentane.
The dissolved oil is after that recovered via evaporating the solvent.
After extraction, the corn oil is then refined using degumming by adding water in order to remove phosphatides.
After the above steps, the resulting corn oil contains fatty acids, phospholipids, pigments, waxes and many impurities that are, then, neutralized using alkali treatment, generally, caustic soda or soda ASH.
Bleaching agents are, then, added to remove color.
The final step is deodorization. It consists of a steam distillation of the corn oil at a temperature between 450°F (232°C) and 500°F (260°C) under a high vacuum.
This helps in removing the volatile compounds that can affect the odor of the final corn oil.
This process kills all the nutrients. Besides, some chemical residues, notably hexane, can remain in the oil, which makes it unhealthy.
Yet, as it is refined in high temperatures, the refined corn oil has a high smoke point, which makes it very valued for foods frying.
In comparison, cold pressed and expeller-pressed corn oil are better for making salads and dressing.
It is important to note that, generally, most corn oils commercialized are refined and go through a chemical process as the yield is very high comparing to the unrefined natural processes.
Following some researches, the healthiest oil is the unrefined oil obtained via either cold pressing or expeller-pressing extraction.
First, these methods of extraction are environmentally friendly and do not use any additional chemicals.
Second, the extracted corn oil preserves its nutritional value in terms of bioactive compounds, antioxidants and is packed with vitamin E.
What are the uses of corn oil?
Corn oil is used in many fields for either cooking applications or non-cooking ones.
Corn oil is a general cooking oil widely used for roasting, baking and deep-fat frying, especially, the refined corn oil, which smoke point is high.
The cold pressed or expeller pressed oil is preferred for salads dressing, sautéing and cold or low temperature preparations like vinaigrettes, sauce, mayonnaise, and others, due to its special taste and its richness in vitamin E.
Corn oil is an important ingredient in many cosmetic applications like soap, shampoos and conditioners, salve, etc. It is also used in skin and hair care products and as a baby oil.
. Pharmaceutical uses:
In pharmaceutical preparations, corn oil is sometimes used as a carrier for some drug molecules.
In the last few years, with the increasing fuel prices, there is a shifting preference towards using oils as biodiesel.The demand for corn oil as biodiesel feedstock has raised significantly.
. Other industrial applications:
Corn oil uses include also paint, inks, nitroglycerin, textiles, metal surfaces’ rustproofing and insecticides.
What are health benefits of corn oil?
Some studies show that corn oil can have beneficial health effects, especially the unrefined one.
1. Contains a significant amount of ubiquinone and vitamin E
Also called vitamin Q10, ubiquinone is a nutrient that the body needs in small quantities to function. It is an excellent antioxidant that contributes in preventing cells from free radicals.
In addition, corn oil is packed with vitamin E especially alpha and gamma-tocopherols.
They are antioxidants that have many benefits on boosting the immune system, preventing blood clots forming, protecting against DNA damage and even some cancers.
It is important to mention that theses nutrients with their highly antioxidant properties protect corn oil from oxidative rancidity. The thing that makes it can last longer on the shelf.
2. Highly effective for lowering cholesterol
Numerous researches show the correlation between corn oil consumption and serum cholesterol reduction.
Corn oil is known as one of the richest source of phytosterols, plant-based compounds that compete with dietary cholesterol and block its absorption by the body’ intestines.
Thus, corn oil can help decrease high levels of cholesterol that is, generally, a leading factor to heart diseases.
3. Rich in phytosterols
Beyond their impact on lowering the cholesterol level, studies show that phytosterols have anti-inflammatory properties.
A diet where anti-inflammatory foods are present may prevent the risk of many diseases like heart issues, diabetes and even some cancers.
The main phytosterol in corn oil is β-sitosterol.
4. May lower the risk of heart disease
Corn oil may promote heart health due to the heart-healthy compounds it contains like vitamin E, phytosterols and omega-6 linoleic acid.
Besides the role of phytosterols and vitamin E, studies show that linoleic acid may lower the risk of coronary heart disease, improve insulin sensitivity and blood pressure.
Indeed, this dietary essential omega-6 fatty acid is necessary for the skin integrity, the immune system and the cell membranes.
What are the downsides of corn oil?
Besides having many potential health benefits, corn oil has some significant downsides that may overweight its beneficial impacts.
1. Has a high omega 6 to omega 3 fatty acids ratio
The ratio of omega 6 to omega 3 fatty acids of corn oil is 46:1 with 54% of omega-6 fatty acids and less than 1,2% of omega-3 ones.
This high level of ratio gives two main data.
First, it is very high in omega-6 fatty acids. Indeed, 1 tablespoon of corn oil contains between 7-8 g of linoleic acid. Thus, if consumed in excess, it will be very harmful for health.
In fact, the World’s Health Organization recommends an omega-6 fatty acids intake between 2,5% and 9% of energy.
Second, the high ratio means an imbalance between omega-6 and omega-3 intake, which is very harmful for the health.
Thus, a lower ratio ideally 1:1, is very desirable in order to reduce the risk of many chronic diseases.
2. Commercial corn oil is highly refined
It is known that the golden light color of corn oil is the primary visible sign that is highly refined.
As explained before, the process of refining oil combines the expeller and solvent process, expelling in continuous screw presses and solvent extraction of the press cake.
Before ending up in a bottle, refined corn oil goes through many processing: degumming, alkali treatment, bleaching, winterization and deodorization.
So, many chemicals are added during these processes like neurotoxin hexane, sodium hydroxide, sodium carbonate, bleaching agents, etc.
Thus, normally, any residue of these chemicals in the extracted oil means that we’re eating these harmful products any time we cook with these oils.
Besides, using high temperatures during the refining process decreases the nutritive value by removing some nutrients and may even lead to the formation of some carcinogenic materials.
What more, exposed to high temperature, polyunsaturated omega-6 fatty acids become unstable. This instability leads to the formation of a configuration of Trans fatty acids thought to affect the blood cholesterol.
3. Commercial corn oil is made with genetically modified corn
Most commercialized corn oils are made by GMO corn. What is very normal if we know that more that 88% of the U.S planted acreage are with genetically modified corn.
Genetically modified means genetically engineered to have special agriculture traits especially being resistant to pesticides and to herbicides.
Many researches link GMO food consumption to the increase of many health issues, allergies and intolerances to many foods.
Besides those problems, GMO version does not comprise the same quantities of nutrients, antioxidants and minerals as the pure organic food.
Is corn oil healthy?
1- Is corn oil a vegetable oil?In general, vegetable oil means any oil extracted from the plant components, typically seeds like soybean, rapeseed that makes the canola oil, Safflower, etc. or even a mix of seeds to have a mix of oils.
Corn oil can also be called a vegetable oil as it is extracted from the corn kernels, the fruits of corn that are considered its grains or its seeds.
2- What is a smoke point and What is the smoke point of corn oil?The smoke point called also the burning point is the temperature at which the vegetable oil or any fat starts to produce a clearly visible smoke. When the oil pasts its smoke points, this means that it will not only give a burnt flavor to foods, but also create free radicals that are harmful for health.
The smoke point of corn oil is 450°F (230°C). It is a high smoke point that makes it good for frying.
3- Why is corn oil generally less expensive than most other types of vegetable oils?The worldwide market of corn oil has seen a rapid grow in the recent last several years and is expected to continue growing to reach 7180 million US$ in 2024. Besides, the production areas of corn oil are generally corn production areas as corn oil is produced in large amount as a co-product of cornstarch.
Consequently, corn oil is less expensive than the other vegetable oils. Indeed, during the same process of extraction, corn oil is extracted from the kernel’s germ and the corn starch is extracted from the kernel’s endosperm.
4- How long does the corn oil last?Following many sources, the answer depends in a large extent to the storage conditions of the oil. For a best quality, corn oil should be stored in a cool and dark place.
If these conditions are accomplished and the corn oil is properly stored :
- For an unopened bottle, it can stay at a best quality for about 2 years (24 months) - For an opened bottle at normal room temperature, it can keep to 1 year.
Yet, to be sure that the corn oil hasn’t gone bad, smell it, taste it and verify that the odor, appearance and flavor haven’t changed.