How Vegetable Oil May Affect Gut and Brain

When we see the word “vegetable” on a label, we might assume it’s healthy. But when it comes to oils and fats, it’s a different story.
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Take a closer look at the labels on products at your favorite grocery store, and you will struggle to find more than a handful that don’t contain vegetable oil. It’s an ingredient found everywhere, from packaged foods to dishes prepared at most restaurants, including takeout.

In 2023, Americans consumed about 12.25 million metric tons of soybean oil, the most common vegetable oil in the United States.
When we see the word “vegetable” on a label, we might assume it’s healthy. But when it comes to oils and fats, it’s a different story. New research suggests that regular consumption of vegetable oil has adverse effects on our guts and brains.

How Vegetable Oil Affects the Brain and Gut

Most “vegetable” oils are actually derived from seeds. When you see a product ingredient simply labeled “vegetable oil,” it is almost always made from pure soybean oil or occasionally a blend of soybean and corn oils.
Recent studies have shown the concerning effects of soybean oil consumption on neurological and gut health in mice. Mouse models are essential for investigating mechanisms related to human health, as our microbiota phyla are 90 percent similar to those of mice.
A study published in September in the Journal of Traditional and Complementary Medicine found severe neuroinflammation and gut damage in mice that had been fed soybean oil compared to those fed lard.
During the 20-week study, researchers observed damage to both the blood-brain barrier (BBB) and intestinal barrier in the soybean oil group. These mice experienced a reduction in beneficial gut bacteria like Akkermansia and an increase in pathogenic bacteria such as Dubosiella, resulting in brain inflammation and damage. Brain inflammation from damage to the BBB has been linked to neurological disorders and neurodegenerative conditions, from depression and sleep disorders to diseases such as Alzheimer’s and multiple sclerosis.
Another study in June 2024 also linked neurological impairments to soybean and corn oil consumption. Mice exposed to these oils from early gestation through adulthood showed impaired locomotor activity, motor coordination, and spatial memory. The researchers observed depression- and anxiety-like behavior, suggesting that neurobehavioral alterations came about due to excessive oxidative stress in the brain.
A separate 2023 mouse study conducted by the University of California (UC) found that soybean oil consumption decreased endocannabinoids in the gut. Endocannabinoids are part of a biological signaling system found in all mammals, consisting of naturally occurring compounds and receptors in the gut and brain.

This system regulates communication between nerve cells in the brain for internal functions such as appetite, memory, stress management, and sleep cycles, effectively bridging body and mind.

The gut microbiome changes were also more significant in mice fed a diet high in soybean oil. Researchers saw a decrease in beneficial bacteria and an increase in harmful intestinal bacteria such as E. coli, which has been linked to inflammatory bowel disease.

“It’s the combination of good bacteria dying off and harmful bacteria growing out that makes the gut more susceptible to inflammation and its downstream effects,” study co-author Poonamjot Deol, a biochemist with a doctorate in cell biology, said in a press release.

Higher Ratio of Unstable Fatty Acids

“Further, linoleic acid causes the intestinal epithelial barrier to become porous,” Deol said.

Linoleic acid, or omega-6, is an essential fatty acid your body needs in the right ratio to produce endocannabinoids. However, an excess of omega-6 fats creates chronic inflammation related to a wide range of human diseases.

This study suggests that the excessive omega-6 found in soybean oil adversely affects the environment required to sustain a healthy gut microbiome. Beneficial bacteria cannot survive with excessive inflammation, which promotes the growth of harmful pathogens.

Overconsumption of linoleic acid also damages the intestinal barrier, allowing toxins to enter the bloodstream. This increases the risk of infections and chronic inflammatory disorders, such as ulcerative colitis.

The UC researchers of the 2023 study also cautioned against the use of corn oil, another widely consumed vegetable oil, as it has the same amount of linoleic acid as soybean oil.

An abundance of omega-6 fatty acids introduces another problem: The more unsaturated omega-6 fatty acids an oil has, the more easily the oil will oxidize when exposed to light and air, and even more easily when exposed to heat. The faster oxidation occurs, the more attacks on your cell membranes, lipoproteins (cholesterol), and every part of your internal body. This damage from a linoleic acid-heavy ratio will promote localized oxidative stress (and inflammation) and hinder your body’s ability to maintain homeostasis. This damage then accumulates in your tissues or fat cells and can lead to a long list of chronic disease states.
A 2018 review found that “numerous lines of evidence show that the omega-6 polyunsaturated fat linoleic acid promotes oxidative stress, oxidised LDL (low-density lipoprotein), chronic low-grade inflammation and atherosclerosis.”

This process doesn’t happen in one week or one month. It takes time for the burden of oxidized omega-6 to build up. Your body can handle some of these spontaneous reactions thanks to its detoxification systems, which use glutathione, antioxidant enzymes (catalase), and vitamins (tocopherol).

This is why when you eat the whole-food forms of these seeds and legumes, there is less of an omega-6 burden. The antioxidants alongside omega-6 present in whole foods protect the cells.

Cooking with these oils compounds the problem, as research shows they produce more unstable toxic compounds, such as aldehydes, when exposed to high heat. Aldehydes are harmful because they are highly reactive with DNA and proteins, and new research links exposure to them to premature aging.

The safe daily intake level of linoleic acid remains undetermined.

It seems to be a case, similar to many others involved in nutrition philosophy, where “the dose makes the poison.” Too much isn’t good for anyone. It is unclear how much vegetable oil a person can consume before it accumulates enough to harm health.

Other Epoch Times articles have discussed the health risks associated with the consumption of seed oils.

Cheap Oil

Soybean oil is the most commonly consumed edible oil in the United States today. It contains much more linoleic acid (about 60 percent) than other plant oils, such as olive oil (less than 13 percent).
Twenty to 30 percent of the average American’s calories come from refined seed oils such as soybean, corn, and canola. Most processed, ready-to-eat foods and fast food contain these inexpensive energy sources.

While you may not use soybean or corn oil at home in your cooking, most restaurants and takeout places use it by default because it’s cheaper. However, many newer eating venues have begun promoting their use of seed-free oils, so it may be worth inquiring about online or calling ahead. An app called Seed Oil Scout helps you locate venues all over the world that use healthier cooking oils.

As a direct result of this increase in vegetable oil consumption, the average American now has a lower intake of anti-inflammatory omega-3 fats. The current amount of omega-3 in your cell membranes can easily be obtained through a home blood test kit or walk-in lab.
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Soybeans comprise over 90 percent of U.S. oilseed production. Additionally, more than 90 percent of U.S. corn and soybeans are produced using genetically engineered varieties.

Soybean oil was never used for cooking or consumed by humans until the 20th century, around World War I. Initially, its primary use was as lamp oil, but later, the oils were used in soaps and for other purposes. Soybeans were part of the human diet only in the form of fermented foods such as tofu, tempeh, and soy sauce.

When we examine the availability and use of these modern oils throughout history, we see that oil is not easy to extract from legumes and seeds. Soybeans are not fruits like olives or avocados, whose juicy oil is much easier to extract. Soybean oil requires processing that typically involves a hexane solvent, which is then evaporated. Trace amounts remaining in soybean oil-containing products have led to consumer concern due to their connection to nerve damage.

Many manufacturers use hydrogenated soybean oil to increase shelf life and enhance flavor in packaged foods. Hydrogenation converts liquid unsaturated fat into solid fat by adding hydrogen. Partially hydrogenated fats contain trans fats, which may be linked to a higher risk of chronic conditions such as cancer, heart disease, diabetes, and more. Check for any mention of hydrogenation on product labels.

Beyond cooking oil, soybean oil is also used to produce lecithin, a popular emulsifier and another ingredient you may wish to avoid, as it comes from the same production method.

Healthier Oils for Gut and Brain

Your body and brain need healthy fats, so you shouldn’t avoid fats and oils completely. When you eat whole foods containing polyunsaturated fatty acids (PUFAs), you also benefit from the natural antioxidants in these foods.

PUFA-rich foods and the seeds from which these oils are derived are not necessarily a problem. The issue lies with refined oils extracted from the seeds.

Evidence suggests that extra-virgin olive oil and avocado oil benefit gut and brain health. These two oils have similar nutritional profiles: They are both high (70 percent to 80 percent) in oleic acid (a monounsaturated fat that is much more stable than polyunsaturated), low in omega-6, rich in polyphenols and antioxidants with anti-inflammatory properties, and have been shown to reverse cognitive deficits.

Other high-temperature-stable cooking fats (albeit with less scientific evidence supporting their health benefits) include coconut oil, ghee, grass-fed tallow, butter, and sustainable palm oil.

Don’t despair. If you’re like Christine and have a family that sometimes wants packaged treats, you can still find a few brands of cookies, chips, and other snack foods in major stores that are made with butter, coconut oil, and whole-food fats ( such as nuts) instead of seed oils.

Consumers are slowly returning to food traditions that are closer to nature, and fortunately, the research is following.
Views expressed in this article are the opinions of the author and do not necessarily reflect the views of The Epoch Times. Epoch Health welcomes professional discussion and friendly debate. To submit an opinion piece, please follow these guidelines and submit through our form here.
Sheridan Genrich
Sheridan Genrich, BHSc., is a clinical nutritionist and naturopath whose consulting practice since 2009 has specialized in helping people who struggle with digestive discomfort, addictions, sleep, and mood disturbances. During her complementary medicine degree at university, Genrich developed a passion for understanding behavioral neuroscience and gut-brain imbalances. Since then she has completed extensive post-graduate certifications in nutrigenomics, polyvagal theory in trauma and other nutritional healing approaches using the "food first" principles. As a highly sensitive person who has learned to thrive again after years of extraordinary adversity, Genrich believes people can unlock their innate potential and heal with the right tools and support. She actively stays up-to-date with evidence-based research while also incorporating ancestral approaches that are personalized and aligned with nature’s rhythms.
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