Soybean Oil 101: Nutritional Values and Research Findings

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Soybean oil is a commercial cooking oil produced by extracting the oil from the seeds of the soybean plant (Glycine max).

This oil is incredibly common, and it is the second most-consumed vegetable oil in the world behind palm oil (1).

However, what does soybean oil offer nutritionally, and it is a good choice of cooking oil?

This article examines the nutritional values and scientific research on soybean oil.

How Is Soybean Oil Made?

Soybeans contain approximately 20% fat by weight, but extracting their oils is quite difficult without the appropriate equipment (2).

Therefore, the majority of commercially produced soybean oil relies on a mechanical and solvent extraction process (3).

This process extracts the edible oil from the soybeans, and the finished product is known as a ‘refined, bleached, and deodorized’ (RBD) oil.

The entire production process is quite long and complex, but here is a quick summary of the primary steps:

  • First, the soybeans go through a mechanical press that uses heat and pressure to extract their oil.
  • After mechanical pressing, there is still residual oil left in the soybean meal, which is then extracted by soaking the soybean meal in a solvent called hexane. The hexane then needs removing before the soybean oil can be sold, and this removal process uses steam and vacuums (4).
  • Following this solvent extraction step, the oil also needs bleaching, This bleaching process removes impurities from the oil (5).
  • Finally, the oil undergoes a deodorization process to remove volatile compounds in the oil. This deodorizing stage involves a high-temperature steam distillation process (180-220°C) (6).

Although this method of oil production may not sound as “clean” as cold-pressed oil, all the solvent residues are removed before the product can be sold.

Additionally, this process is not unique to soybean oil.

For example, there are many different vegetable oils (such as Canola oil and refined olive oil) that undergo refining, bleaching, and deodorization processes.

Key Point: Most commercial soybean oil is refined, bleached, and deodorized.

Nutrition Facts

Based on data from the USDA FoodData Central Database, the following table shows the nutritional values for a tablespoon (13.6 gram) serving of soybean oil (7).

Daily values have been calculated using the FDA’s latest published daily values (8).

Soybean Oil Nutrition Facts (Per tbsp)
NameAmount% Daily Value
Calories120 kcal6%
Carbohydrate0 g
Fat13.6 g20.9%
  Saturated2.1 g
  Monounsaturated3.1 g
  Polyunsaturated7.8 g
    Omega-30.9 g
    Omega-66.9 g
Protein0 g
Vitamin E1.11 mg7%
Vitamin K25.0 mcg21%

Despite not being a major source of vitamins or minerals, soybean oil does provide moderate amounts of vitamin E and K.

The five primary fatty acids in soybean oil are as follows (9):

Saturated

  • Palmitic acid
  • Stearic acid

Monounsaturated

  • Oleic acid

Polyunsaturated

  • Linoleic acid (omega-6)
  • Linolenic acid (omega-3)

Linoleic acid is the predominant fatty acid in soybean oil.

Key Point: As shown in the nutritional values, soybean oil is primarily a source of omega-6 polyunsaturated fat.

Smoke Point

Soybean oil has a smoke point of 234°C, which is approximately 453°F (10).

The smoke point of a cooking oil represents the temperature at which it starts to smoke. For instance, if soybean oil reaches the ‘smoke point’ temperature during cooking, it will start to burn.

Unfortunately, when oil reaches its smoke point, the degrading oil can produce potentially harmful oxidation products such as acrolein (11, 12).

It is important to note that the smoke point of a cooking oil very much depends on the amount of free fatty acids (FFAs) present. A higher amount of FFAs results in a lower smoke point and in turn, a lower level of FFAs means a higher smoke point (13).

Since the refining process largely removes free fatty acids from oil, refined oils tend to have a higher smoke point than unrefined oils. For this reason, soybean oil has a higher smoke point than cold-pressed extra virgin olive oil (14, 15).

Oxidative Stability

Another consideration to be aware of is that the given smoke point of cooking oil actually reduces during heat exposure. Also, this rate of decline depends on the oxidative stability of the specific type of cooking oil (16).

For this reason, the smoke point alone isn’t necessarily the best indicator of how heat-stable a particular oil is.

Various different factors affect the oxidative stability of a specific oil, and these include:

  • Degree of saturation
  • Polyphenol content
  • Amount of antioxidants (such as vitamin E) present

Firstly, out of the three main types of fatty acids, saturated fats are the most stable when exposed to high heat temperatures (17).

This is because they are “fully saturated.”

In other words; the carbon atoms in the fat are tightly surrounded by hydrogen atoms, which helps to prevent oxygen from ‘oxidizing’ the carbon atoms.

The Structure of Saturated Fat.
The molecular structure of saturated fat

On the other hand, polyunsaturated fatty acids have numerous double bonds (gaps) exposing the carbon atoms to oxygen.Molecular Structure of Polyunsaturated Fat.

This means that instead of linking to a hydrogen atom, the carbon atom has two links with another carbon atom.

However, this ‘double bond’ makes polyunsaturated fatty acids more prone to oxidation.

As shown in the diagram above, this particular polyunsaturated fatty acid has two double bonds. Others may have more.

For this reason, soybean oil has poor oxidative stability compared to fats with a higher degree of saturation, such as butter, extra virgin olive oil, and avocado oil.

Key Point: Due to its large amount of omega-6 fatty acids, soybean oil is not heat-stable and is prone to oxidation.

Studies On Soybean Oil’s Oxidative Stability

One study investigated the rates of oxidative deterioration for soybean oil, corn oil, and olive oil. After using the oils for frying at 180°C, soybean oil oxidized more (and faster) than the other two oils (18).

Another study showed that heating soybean oil at 185°C (365°F) for two hours led to the formation of 4-hydroxy-2-trans-nonenal (HNE). HNE is an oxidation product that has mutagenic and cytotoxic properties (19).

Additionally, in a rat study, prolonged intake of re-heated soybean oil caused the rats to develop high blood pressure and vascular inflammation (20).

Of course, rats are not humans, and we should try not to re-heat any oil. That said, it is not unusual for fast food restaurants to use (or re-use) oil for extended periods.

Furthermore, a study examined the oxidative stability of soybean oil during storage. This study found that blending soybean oil with other oils, including sesame oil and peanut oil, made it more stable (21).

The researchers concluded that the greater oxidative stability of the blended oil was likely because polyunsaturated fatty acids decreased while monounsaturated fatty acids increased.

Key Point: Soybean oil is a rich source of polyunsaturated fatty acids, and is thereby not as heat-stable as some other cooking oils.

Excessive Soybean Oil Intake and Obesity

Look around, and it’s clear to see that Western society has an obesity problem.

For instance, 2 out of every 3 adults in the United States (68.8%) are either overweight or obese (22).

Some people lay the blame for this on red meat and animal fat, but the data does not support this.

Graph showing how red meat consumption and poultry has changed over the past several decades.
(Source)

As you can see, the consumption of red meat has fallen over the past several decades while leaner poultry increases in popularity.

Rates of sugar consumption, which is often a scapegoat for almost every health condition, have also been decreasing since the 1990s (23).

However, if we are looking for a possible dietary villain, then soybean oil consumption has grown by a significant magnitude.

It is in almost everything we eat; not only as a cooking oil but also in salad dressings and processed foods.

Specifically, domestic consumption of soybean oil has more than quadrupled from 1,652,000 tons in 1964 to 6,576,000 tons as of 2016 (24).

If we go even further back, soybean oil consumption increased 1000-fold between the years 1909 and 1999 (25).

Animal Studies Suggest Soybean Oil Could Be Obesogenic

If excessive soybean oil intake is helping to drive the obesity crisis, then isn’t that all just about calories in vs. calories out?

Well, calories certainly matter, and soybean oil contributes a substantial number of them to our daily diet.

However, some animal studies suggest that there could be more to it;

  • A mouse study compared the impact of a diet high in soybean oil to high fructose and coconut oil diets. In this study, the mice fed large amounts of soybean oil had statistically significant greater weight gain, diabetes, and insulin resistance. Additionally, the soybean oil diet upregulated cancer, inflammation and obesity-related genes (26).
  • Another animal study fed mice a high-fat diet of either soybean, olive oil, MCT oil, peanut oil, or tea oil. Following the study, body weight and body fat were significantly higher in the soybean oil group compared to all others.  Also, the soybean oil group had visible fatty liver disease—the MCT, olive oil, and tea oil mice did not (27).
  • In a study comparing butter and soybean oil, fat oxidation increased in the group fed butter. In the soybean fed group, subjects showed an inability to oxidize fat while resting (28).

Are these animal studies proof that soybean oil is obesogenic in humans?

Of course not, but with a lack of human trials on this issue, these animal studies certainly suggest it is worth looking into.

Key Point: Animal studies show that soybean oil uniquely causes obesity and diabetes compared to other fats. There is no evidence that this would be the same in humans, but it is perhaps an area for further research.

Refined, Bleached and Deodorized Oils May Contain Hexane Residues

Soybean oil manufacturers state that the finished oil doesn’t contain an appreciable amount of hexane because of the cleaning and refining process the oil undergoes.

However, studies show that residual amounts usually remain in the finished oil. Based on equivalent-dose animal studies, these amounts are safe for human consumption (29).

That being said, independent tests have investigated the issue and shown that hexane residues “10 times higher than what the FDA considers normal” can appear in soy products (30).

Additionally, the FDA has set no maximum values on hexane residues in soy products, and FDA regulation does not require testing vegetable oils for hexane contamination (31).

Key Point: Soybean oil may contain residues of the chemical solvent hexane.

Soybean Oil Promotes the Excessive Omega-6 To Omega-3 Ratios In Our Diets

As previously mentioned, soybean oil is a significant source of omega-6 fatty acids.

Although both omega-3 and omega-6 are essential fatty acids, some researchers believe we should consume them in relative balance.

For example, research shows that ancestral diets generally had an omega-6 to omega-3 ratio approaching 1:1 (32).

Due to the excessive amount of vegetable oils in the modern diet, people are consuming more omega-6 (and less omega-3) than at any point in human history.

Notably, estimates place the modern diet as having an omega-6 to omega-3 ratio of 20:1 or higher (33).

Omega-6: Healthy Until It’s Not?

Picture of a woman suffering from inflammation related back pain.Omega-6 is an essential fatty acid that is pro-inflammatory, and this is a good thing.

For instance, some inflammation in the body is necessary for healing cuts and wounds.

However, in excessive amounts, some research suggests that it may cause our body to stay in an inflammatory state — and chronic inflammation is a known risk for the majority of illnesses (34).

On this note, studies suggest that this excessive intake of omega-6 could cause the following problems;

  • As omega-6 competes with omega-3 for uptake into our cells, too much omega-6 could mean a deficiency of anti-inflammatory omega-3 (35).
  • Studies show that a lower dietary omega-6 to omega-3 ratio reduces inflammation and mortality risk from heart disease (36).
  • Chronic diseases such as diabetes, obesity, IBD and arthritis all have associations with increased omega-6. Imbalances in the omega 6 to 3 ratio have likely increased the prevalence of multiple inflammatory, disease-causing processes (37).

That said, this excessive omega-6 content is not a problem unique to soybean oil. Other oils rich in polyunsaturated fats such as grapeseed oil have the same problems.

Key Point: Soybean oil is in almost everything and significantly contributes to the excessive amounts of omega-6 in our diet. Some research suggests that this may have adverse health effects.

Soybean Oil Has Changed the Fatty Acid Composition of our Cells

Graph showing the rise in polyunsaturated fat consumption in the United States over the last century.
(Source)

The above graph shows the explosion in the consumption of polyunsaturated fat over the past century.

As soybean oil is the most significant source of omega-6 in the US, it is a significant part of this trend.

Excessive Omega-6 Intake May Cause Problems

As discussed, polyunsaturated fats have several double bonds, which means their carbon atoms are susceptible to oxidization.

The first thing to remember here is that our cells and tissues predominantly contain saturated and monounsaturated fat.

For one thing, this makes the fat in our cells stable. Just like vegetable oils can oxidize due to air, light, or heat exposure, so can fats inside our body.

One theory speculated on by researchers is that as our cell membranes incorporate a higher amount of polyunsaturated omega-6, they become less stable.

Several studies on soybean oil/omega-6 seem to offer some support for this theory;

  • Omega-6 is a “melanoma stimulator” because it makes our skin cells susceptible to damage from UV rays (38).
  • An animal study separated mice into different groups and fed them varying amounts of dietary omega-6 PUFA. The higher their dietary intake, the more they developed cancerous tumors (39).
  • One study fed female rats either soybean oil or ghee as 10% of their total diet. The soybean oil group had higher tumor incidence (65.4% versus 26.6%), larger tumor size, and more rapid onset of cancer (40).
Key Point: Excessive amounts of omega-6 change the fatty acid composition of our cells.

Final Thoughts

Overall, there is a lack of direct evidence from human trials to claim that soybean oil is harmful with any certainty.

However, in my view, many studies justify being wary about the potentially detrimental effects soybean oil can have.

Especially when we consider just how much of this oil many people consume.

To summarize; soybean oil is prone to oxidation, offers predominantly omega-6 fatty acids, and has links to adverse health effects in animal studies.

With all this being said, it is probably a better idea to opt for cooking oil that does not have these concerns.

Fruit oils such as avocado, coconut, and olive oil appear to be a good choice since studies show these oils have much better oxidative stability.

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Jorge
Jorge
1 year ago

@Michael Joseph. Thank you for a well-written and informative article. I have a question about avocado and its oil. I have read elsewhere that avocado fruits, in spite of their otherwise richness in other nutritional elements, are very high in Omega-6 vs Omega 3. I don’t remember the exact figure but I think its somewhere around O-6:O-3 = 25:1 which is well above the commonly accepted beneficial level of 1:1 as you have pointed out. Realizing the adverse heath effect of excessive O-6, I have asked quite a few health/nutrition experts why avocado fruit, with its high ratio of 25:1,… Read more »

Hector
Hector
1 year ago

I bought a multivitamins and minerals supplement and on the box says antioxidant. Then I read the ingredients and the first ingredient is soybean oil and thought something is wrong here. Why those laboratories have to put soybean in multivitamins and minerals supplements? Thanks for the info!

tracy
tracy
1 year ago

wow – even the low carb foods all have soy bean oil – so frustrating– great article, thanks

Kris Grauel
Kris Grauel
1 year ago

I was prompted to read this article because I bought some tuna with soy bean oil in it by mistake. I will make sure going forward that whenever I buy tuna it is in water only.

Cindy
Cindy
2 years ago

As they point out, it’s hard to avoid. High time for the public to demand our food no longer be contaminated with this toxic industrial oil. There seems to be very little awareness out there of how it is put in just about everything. It makes great candles though…:)

Denise
Denise
2 years ago

Hi. I was wondering what might make dogs develop tumors quickly. My dog’s diet only consists of dog food and water. He’s a 12 year old Miniature Schnauzer and has started developing many fatty tumors. I have only been giving him filtered water and am now looking to the food I buy and looking even more closely to what’s in it. I feed him Castor & Pollux brand which includes 3% Omega-6 and saw in your article this was known to increase tumors in animals consuming high Omega-6. I was wondering if there was connection and if Soybean Oil in… Read more »

Javier
Javier
2 years ago

Obesity in the US has everything to do with hydrogenated vegetable oils (forbidden in Europe and only very recently forbidden in the US too), and using fructose syrup instead of natural sugar.
It has nothing to do with using vegetable oils. The vegetable oil market in the US is extremely deceptive

A. K.M Mohiuddin
A. K.M Mohiuddin
2 years ago

Thanks for the valuable information which is very important for people’s awareness about use of soyabean oil in food. We will be alerted in future about this oil. Thank you very much.

Pete Moss
Pete Moss
1 year ago

This makes me question why so many want the government controlling everything. If soy bean oil is so bad for me, why does the FDA allow the use of it?

Dejavu
Dejavu
2 years ago

Great article! Thanks!

Where can we get some extra Omega-3s to counterbalance the extra Omega-6 ?

I was buying Sunflower oil in lieu of canola and now need to find avocado oil that isn’t in a spray. Coconut and olive impart too much odd flavor when you are baking a cake!
I wonder will avocado oil?

Rita Wright
Rita Wright
1 year ago
Reply to  Dejavu

Try refined coconut oil it has no taste. It is inhumane the way they market soy products claiming how healthy they are. I feel health food is another racquet of destruction for profit only. Soy also affects the way you think…mood swings, hostility. Also makes you feel weak and fatigued.

Roe
Roe
2 years ago

Why don’t people just workout? Always playing blame game

Shay
Shay
2 years ago

You are absolutely right. They do use canola or sometimes sunflower oil. I guess for me soybean oil has always been the worst but I know that canola isn’t a great option either.

EG
EG
2 years ago
Reply to  Shay

Olive Oil, Walnut, Coconut and Sunflower are good choices. Mayo, Best Foods and others that contain soybean oil are poisonous. They are all trying to poison us.

Jessie
Jessie
2 years ago

Interesting, Chinese have consumed thousands of years soybean oil and they are definitely slimmer than the people from the USA. There are so many dietary, environmental, genetic factors which affect people’s health. it is overgeneralization by saying overweight of US people due to increased consumption of soybean oil. Soybean is not the only contributor to the mentioned diseases. By the way, there is also production procedure for soybean oil called ‘’cold pressing”.

Shay
Shay
2 years ago
Reply to  Michael Joseph

Well said Michael and a great article. In most European countries soybean oil can almost never be found in the ingredients. Shocked when I moved to the US and saw that there is soybean oil in almost every loaf of bread that I found!

EG
EG
2 years ago
Reply to  Jessie

They also have the highest rate of stomach cancer…..known fact.

jeff
jeff
2 years ago

used this for my science fair project thank you so much

Lisa Dietrich
Lisa Dietrich
3 years ago

Thank you for posting this informative and valuable article. I loved the way you would use the subjects and share their individual links. This article is a “keeper” for sure. It’s one that needs to be read several times as to retain the information stated here. God bless.

Linda
Linda
1 year ago
Reply to  Michael Joseph

You haven’t mentioned anything about organic soybean oil is it equally bad?