- Soybean oil encompasses 57% of all cooking oils used in the United States, and 30% globally.
- More than 50% of soybean oil is made of an omega-6 fatty acid called linoleic acid.
- Past studies show that consuming too much soybean oil or omega-6 fatty acids may increase your risk for certain health concerns, such as obesity.
- A new study sheds light on how soybean oil might contribute to a person’s obesity risk.
According to the U.S. Soybean Export Council, soybean oil encompasses 57% of all cooking oils used in the U.S., and 30% globally.
Commonly labeled in grocery stores as “vegetable oil,” soybean oil is mainly made from polyunsaturated fatty acids and contains the essential omega-3 fatty acid alpha-linolenic acid, as well as the omega-6 fatty acid known as linoleic acid. More than 50% of soybean oil is made of linoleic acid.
Previous studies show that soybean oil may offer some heart-health benefits. For instance, a study published in September 2021 found that replacing saturated fats with soybean oil may help lower a person’s
However, other research offers evidence that consuming too much soybean oil or omega-6 fatty acids may increase your risk for certain health concerns, including ulcerative colitis, neuroinflammation, type 2 diabetes, dementia, and obesity.
“Cooking oils are an integral part of our food system and are used not only for cooking in home kitchens, but also in restaurants,” Sonia Poonamjot Deol, PhD, assistant professional researcher at the University of California, Riverside, told Medical News Today.
“They are also increasingly being incorporated into processed and ultra processed foods. Increased consumption of [certain] fats is linked to the development of many metabolic and inflammatory diseases, including obesity. Therefore, understanding the role that cooking oils, especially soybean oil, which is the most widely consumed edible oil in the U.S. and the second most widely consumed edible oil globally, can have on the development of obesity is critical,” Deol explained.
She is the co-corresponding author of a new study recently published in the Journal of Lipid Research that sheds light on how soybean oil might contribute to a person’s obesity risk.
For this study, researchers focused on a genetically-engineered — or transgenic — mouse model. These mice create an altered version of the liver protein HNF4α. This protein plays an important role in the development and function of not only the liver, but the pancreas and lower gastrointestinal tract as well.
According to researchers, this form of HNF4α normally only exists in humans under specific conditions, such as due to a chronic illness or metabolic stress.
“From our previous studies we knew that these transgenic mice have lower than normal gene expression for the enzymes that are involved in converting linoleic acid into the pro-inflammatory oxylipins,” Deol explained. “We therefore hypothesized that these mice would not get obese on the soybean oil diet because they would have decreased oxylipin production.”
At the study’s conclusion, Deol and her team proved their hypothesis by discovering that transgenic mice fed a high soybean oil diet gained significantly less weight when compared to a normal mouse model fed the same diet.
Additionally, the transgenic mice showed fewer oxylipins, Healthier livers, and enhanced mitochondrial function when compared to regular mice on the same diet.
“These findings provide us with the mechanism by which soybean oil causes obesity in mice,” Deol said. “We have also identified the molecular pathways that are involved in soybean oil-induced obesity; this information can be used in the future for the development of preventive and therapeutic strategies against metabolic diseases.”
“Consuming small amounts of soybean oil is perfectly safe and provides a good source of the essential fatty acid linoleic acid,” she continued.
“Soybean oil is not a toxic substance. The problem is that by virtue of it being used in home and restaurant cooking, in animal meals and in processed foods we are taking in much higher levels of linoleic acid than our body needs. This could be leading to excessive accumulation of oxylipins in our body which can then lead to increased obesity and inflammation. Thus, we need to restrict our total linoleic acid intake to 2–3% of the daily caloric intake, and to restrict overall fat consumption (from any type of fat) to the recommended daily amount.”
– Sonia Poonamjot Deol, PhD
MNT had the opportunity to speak with Mir Ali, MD, a board-certified general surgeon, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, about this study.
Ali, who was not involved in the research, commented that he thought this was an interesting study that sheds some light on how soybean oil may contribute to obesity.
“However, this is a very controlled study in an animal model that may not necessarily work the same in humans,” he continued. “The more information and research on the effects of different cooking oils will help in determining the best oil for cooking. Soybean oil is widely used but has been shown to have detrimental effects, so finding the best alternative would be beneficial.”
“The next step would be to devise a study looking at the effects in humans and the mechanism behind the detrimental effects of soybean oil,” Ali added.
For those who may want to try reducing the amount of soybean oil they consume in their diet, Monique Richard, MS, RDN, LDN, a registered dietitian nutritionist and owner of Nutrition-In-Sight, offered her top tips.
“Soybean oil is high in omega-6 linoleic acid, which itself, as part of a balanced dietary pattern, is not harmful,” Richard explained. “But much of [the] soybean oil used in the U.S. is highly refined, stripping antioxidants and flavor compounds. It is also the amount consumed, its paired partners, and the process by which soybean oil is derived that raises concern.”
To help reduce a person’s soybean oil consumption, Richard recommended:
- Read ingredient lists, not front-of-package claims. If soybean oil, vegetable oil, or canola oil appear in the first few ingredients, that food is likely heavily processed. There may be a more wholesome option or healthier alternative.
- Choose whole foods over ultra-processed snacks. The largest source of soybean oil in the American diet is not home cooking — it’s commercial packaged foods, fried foods, and restaurant offerings. Use fresh, frozen, or canned produce when possible. Look for whole grain options like oats, bulgar, quinoa, and brown rice versus pre-packaged noodles, crackers, or pasta kits.
- Cook more at home, even 1–2 meals per week. That way you have control over the ingredients, sodium, sugar, and oils used. Look for recipes that have simple, whole ingredients that) can be batch cooked for more meals later in the week.
- Swap frying for roasting, sautéing, grilling, or air-frying. These methods both reduce oil use and total calorie density.
- Choose whole soy foods for natural goodness. Foods such as tofu, tempeh, or soybeans in their pod, aka edamame, are not part of this concern. They are nutrient-dense, fiber-rich, and associated with many health benefits.
Richard offered these tasty soybean oil alternatives, which also have added benefits:
- olive oil (extra-virgin, cold-pressed) — great for dressings, marinades, and cooking; benefits have been identified in numerous research studies related to heart and cognitive health
- avocado oil — neutral flavor, tolerates higher heat, great everyday option
- sesame or peanut oil — a slightly nutty flavor and aroma; excellent in Asian, African, and Middle Eastern-inspired dishes; delivers antioxidants and polyphenols while complimenting flavor profiles of other herbs and spices.
- walnut or flaxseed oil — for use at cool or room temperature to top parfaits, desserts, or make dressings.
“The components of our meals matter to our molecules — let’s make the best choices we can,” said Richard.
