A popular form of vegetable oils, soybean oil is extracted from soybean seeds.1 There has been much hype about its touted health benefits, but there's more to soybean oil than what's advertised on product labels. It could be very problematic to use in cooking, due to manufacturing processes and the presence of genetically engineered varieties. Get the lowdown on this food staple, and why it is one of the worst oils for cooking.
What is soybean oil?
Soybean oil is extracted from soybean (Glycine max) and often has a dark yellow or faint green color. Standard vegetable oil is typically composed of soybean, corn, safflower and palm oils.2
The first domestic use of soybeans is traced to the eastern half of North China in the 11th century B.C., although as early as 2853 B.C., the plant was considered a sacred plant of China along with rice, wheat, barley and millet. By 1895, Chinese soybean production expanded overseas when the Japanese began importing soybean meal to serve as fertilizer.3
Soybean shipments to Europe began around 1908, although Europeans had been aware of soybeans as early as 1712. The story of soybeans in the United States began in the early 1800s, with North Carolina having one of the first soybean plantations.4
As of 2016, Americans were consuming more than 28 billion pounds of edible oils annually, with soybean oil comprising about 80 percent of that number. Worsening the problem further at the time was that soybean oil was highly processed and hydrogenated.5
Among the problems with partially hydrogenated soybean oil is trans fat and the health hazards of the soy itself, as well as the prevalence of genetically engineered soybeans. According to the U.S. Department of Agriculture (USDA), 94 percent of soybeans today are grown using herbicide-tolerant seeds.6
Thankfully, in an effort to address health concerns that partially hydrogenated oils (PHOs) — the primary dietary source of trans fats — could be causing thousands of heart attacks and deaths each year, the FDA decided in 2015 that PHOs no longer should be considered "generally recognized as safe (GRAS), and started a campaign wherein food manufacturers were given three years to phase out trans fat from their products, with the ban officially taking effect on June 18, 2018.
This marked a turning point for public health, as The Washington Post reported that trans fat consumption soon drastically lowered. Between 2015 and 2018, companies were able to remove 98 percent of trans fat from the market.7 Later, in a gesture to allow what they called "an orderly transition in the marketplace," the U.S. Food and Drug Administration extended the date for these foods to get completely off grocery store shelves to January 1, 2020.8
Uses of soybean oil
The USDA notes that processed soybeans are the second largest source of vegetable oil — close behind palm oil — as well as the largest source of protein for animal feed.9 It is also the primary source of biodiesel in the country, making up 52 percent of domestic production.10
Lecithin, a product extracted from soybean oil, is a natural emulsifier and lubricant used in many foods, as well as commercial and industrial applications. As an emulsifier, it helps products maintain a smooth quality because it binds two disparate chemicals together.11
Soybean oil is commonly used to make mayonnaise, salad dressing, margarine and nondairy coffee creamers.12 It is also a mainstay ingredient in many processed foods, which is where the problem begins: Processed foods are perhaps the most damaging part of most people's diets, contributing to the occurrence of disease and poor health.
Partially hydrogenated soybean oil was one of the primary culprits in processed foods because of its trans fat content, a substance that can damage your health by increasing your LDL cholesterol levels while simultaneously lowering HDL cholesterol levels, as well as causing a host of other health-related concerns.13
But since the banning of trans fat, companies have been looking for new ways to produce "healthier" soybean oil, such as making it from high-oleic soybeans. These specially made soybeans were created to not need to undergo hydrogenation when processed; thus, no trans fats are formed.14 Oleic acid, such as the that found in olives, has been linked to lowered risk of heart disease.15
However, be aware that high-oleic soybeans are genetically modified, such as Monsanto's Vistive Gold (MON 8775).16 According to a report published by GenØk, a Norwegian foundation that monitors safe consumption of biotechnologies, review officials assert that Monsanto is not entirely honest about their claims about their product's benefits.
The report cites improper assumptions, weakness in study design, lack of information on potential adverse events and improper use of comparators as some of the major concerns, concluding that the company should provide more information to properly assess the risk of MON8775 to public health.17
Composition of soybean oil
Soybean oil contains the following phytosterols:18
- 7-ketositosterol
- 5α,6α-epoxysitosterol
- 7-ketocampesterol
- 5α,6α-epoxycampesterol
- 7-ketostigmasterol
- 5α,6α-epoxystigmasterol
Phytosterols are naturally found in plant cell membranes,19 but are susceptible to plenty of oxidation due to processing. Phytosterol oxidation products (POPs) have been found in coffee, flour, foods made from fried potatoes and vegetable oils. Research has shown that POPs have mutagenic and carcinogenic properties.20
Per 100 grams of soybean oil, there are 15.6 grams of saturated fat, 22.8 grams of monounsaturated fat and 57.7 grams of polyunsaturated fat. The omega-6 to omega-3 ratio is also incredibly unbalanced — 50.422 to 6.789 grams.21
How soybean oil is manufactured
During the early years of soybean oil production, mechanical pressing was used. It used pressure and heat to extract the oil, but this produced low amounts of the final product, as well as low-quality oil itself. As time went on, hexane extraction was used, creating a 99 percent recovery rate. The hexane-to-bean ratio is disparate, typically 5- to 10-to-1, which has led to environmental and health issues.22
Hexane is a colorless liquid with an odor similar to petroleum,23 and is a byproduct of gasoline refining. In the past, soybean oil was, quite simply, made by bathing seeds in this chemical.24 The U.S. Environmental Protection Agency (EPA) classifies hexane as a Hazardous Air Pollutant (HAP), with side effects such as dizziness, nausea and headache. Long-term exposure can lead to blurred vision, muscular weakness and numbness.25
According to a group of soybean industry leaders, the new high oleic soybean oil "is developed through biotechnology … [to contain] 20 to 60 percent less saturated fat" than the original soybean oil, and 75 percent less than palm oil.26
Its processing methods are designed to replace hydrogenated oils with techniques such as interesterification, which rearranges fatty acids among triglyceride molecules, or blending, which mixes trans-fat free hydrogenated soybean oil with a non-hydrogenated oil, a trait-enhanced (genetically engineered) oil or alternative vegetable oils.27
Why soybean oil is bad news for your health
What is it about trans fat that makes it unhealthy and resulted in it being banned for human consumption? There are many reasons why trans fat is bad for your health, with research published in the following areas:
- Cancer — Long-term consumption of foods high in trans fat was found to increase your risk of various cancers by causing chronic inflammation and oxidative stress.28
- Diabetes — Trans fat increase insulin resistance, thus leading to a higher risk of developing diabetes.29
- Heart disease — Research indicates that trans fat increases your LDL cholesterol levels,30 which can clog your arteries.31
- Inflammation — Trans fatty acids have been linked to systemic inflammation, according to a study published in 2006.32
- Weight gain — Published research suggests that consumption of trans fat can increase weight gain and abdominal fat, despite comparable caloric intake.33
- Reproductive health — Experiments indicate that trans fat in the sperm can adversely affect spermatogenesis.34
- Interfering omega-3 synthesis — A study published in PLOS One indicates that trans fatty acids disrupt the production of omega-3 fatty acids in your body, an effect that can increase aggression or irritability.35
Even if soybean oil is used with the best intentions, it can still endanger your health. In a 2019 study that used soybean oil as the primary fat for the research, high-fat diets were deemed undesirable because they change your gut microbiota and increases the production of pro-inflammatory markers.36
What the study failed to mention is that, on the contrary, high-fat diets can actually benefit you, as long as you consume healthy fats from nutritional sources — and soybean oil is not one of those sources.
What the study failed to take into account is the high omega-6 content found in soybean oil. This fatty acid has been linked to increased inflammatory markers, heightening your risk of diseases such as atherosclerosis, inflammatory bowel disease, rheumatoid arthritis and Alzheimer's disease.37
Soy itself poses several significant issues. Aside from being genetically engineered, it has substances that carry potential health problems. These include:
- Goitrogens — Substances that block the synthesis of thyroid hormones and interfere with iodine metabolism.38
- Isoflavones — Isoflavones found in soy may cause overt thyroid toxicity.39
- Phytic acid — Soy contains phytic acid, which inhibits the absorption of certain minerals, such as iron. In one study, iron absorption increased as much as five times when phytic acid was reduced.40
- Anti-nutrients — Soy contains various components that can hamper growth, such as protease inhibitors. Lectins are another antinutrient, which can interfere with the absorption of important nutrients.41
Side effects of soybean oil
Beware of soy allergy, which can happen in very young infants fed soy-based formula. Most children outgrow this issue once they grow older, but in some, it can last until adulthood. Symptoms include:42
- Hives
- Swelling of the lips, tongue, throat or other body parts
- Wheezing
- Abdominal pain
- Skin redness
Through the risks and negative effects I've outlined above, I want to make it clear that you are better off avoiding soybean oil and other vegetable oils for cooking, as well as totally eliminating processed foods from your diet. The high amounts of omega-6 fats in soybean oil can increase your risk of inflammation, which can lead to a host of other health problems.43
Replace your soybean oil with coconut oil for better health
Even if soybean oil today is made from high-oleic soybeans, its genetically modified origins and high-omega 6 content still make it an unviable choice for cooking food. I highly recommend using coconut oil instead of soybean oil, as it is far superior and is loaded with healthful properties.
In addition, use organic butter (preferably made from raw, grass fed milk) instead of margarine and vegetable oil spreads. Butter does not deserve a bad rap, as it offers an array of wholesome benefits thanks to its healthy fats.