Consuming high levels of soybean oil has been associated with diabetes and obesity and potentially depression, anxiety, Alzheimer’s disease, and autism. Now add to this increasing list a type of inflammatory bowel disease known as ulcerative colitis, characterized by long-term large intestine inflammation.
Researchers looked at the gut of mice routinely given a soybean oil-rich diet for about 24 weeks in the laboratory. A decrease in beneficial bacteria was observed as well as an increase in harmful bacteria, particularly adherent invasive Escherichia coli, conditions that could result in colitis.1✅ JOURNAL REFERENCE
DOI: 10.1080/19490976.2023.2229945
The most widely used edible oil in the U.S. is soybean oil and it’s being made use of more and more in other countries, especially India, China, and Brazil. Soybean production became popular in the 1970s in the U.S. to be used as animal feed and soybean oil was a byproduct of the growing growth trend. Soybeans, a great source of protein, are inexpensive and easy to grow.
The study challenges the belief that a lot of chronic diseases originate from consuming excess animal product saturated fats, and that, in contrast, plant derived unsaturated fats are always more healthy.
The researchers said it’s the soybean oil’s linoleic acid that’s the primary issue. While the body requires 1 to 2% of linoleic acid every day, according to the paleo diet, nowadays 8 to 10% of the average American’s energy intake is derived from linoleic acid every day, the majority of it coming from soybean oil. Excessive consumption of linoleic acid is harmful to the gut microbiome.
The researchers observed that a soybean oil-rich diet promotes adherent invasive E. coli growth in the gut. Adherent invasive E. coli makes use of linoleic acid as a carbon source for fulfilling its nutritional requirements. Also, some of the gut’s beneficial bacteria aren’t able to survive linoleic acid and they die off, which leads to harmful bacteria proliferating. Adherent invasive E. coli has been found to result in inflammatory bowel disease in people.
It’s a combination of the good bacteria dying off and the proliferation of harmful bacteria that increases the gut’s susceptibility to inflammation and its subsequent effects. Linoleic acid also results in the epithelial barrier of the intestine becoming porous.
The intestinal epithelium’s barrier function is essential for healthy gut maintenance; it could become more permeable or leaky when disrupted. Toxins can then leak from the gut and go into the bloodstream, significantly increasing infection risk as well as the risk of chronic inflammatory diseases like colitis.
The increase in inflammatory bowel disease corresponds to the soybean oil consumption increase in the U.S. and the researchers theorize that the 2 may be associated.
It’s commonly thought that all unsaturated fats are healthy. Individuals consequently thought that soybean oil is healthier to consume and completely safe compared to other kinds of oils.
The soybean oil used for this study had 19% linoleic acid, which is an essential fatty acid. It’s recommended by the AHA that 5 – 10% of calories consumed every day be derived from omega-6 polyunsaturated fatty acids like linoleic acid to ensure that the heart remains healthy. A lot of seed oils such as sunflower and safflower are linoleic acid sources.
No animal can produce linoleic acid and it has to come from the diet. A modest amount of it is required by the body. But simply because something is required doesn’t mean lots of it is healthy. A variety of the body’s membranes such as those found in the brain need linoleic acid for proper cell function.
Smaller amounts of linoleic acid are found in the healthier olive oil, and it doesn’t make the mice susceptible to colitis as soybean oil does.
Adherent invasive E. coli plays a role in inflammatory bowel disease in people, and the fact that this E. coli was found in these mice is of concern. It can sometimes be unclear how research performed in mice corresponds to humans, but it’s quite apparent in this study.
The researchers also found that the mice given a soybean oil-enriched diet experienced a decrease in endocannabinoids in the gut, cannabis-like molecules that are naturally created by the body to manage numerous types of physiological processes. The gut simultaneously exhibited an increase in oxygenated polyunsaturated fatty acids that manage inflammation which are known as oxylipins.
It has previously been observed that liver oxylipins are associated with obesity. Some studies have also observed oxylipins to be bioactive in colitis. The current study concludes that a diet rich in soybean oil like the current American diet leads to an increase in levels of oxylipin in the gut and a decrease in levels of endocannabinoids, which is in line with inflammatory bowel disease in people.
The majority of processed foods contain soybean oil, possibly explaining why a lot of people in America consume more linoleic acid than the recommended allowance. The majority of U.S. restaurants also make use of soybean oil as it’s relatively cheap.
