Soybean Oil is Bad for Gut Health

Soybean oil consumption has been connected to obesity and diabetes, as well as autism, Alzheimer’s disease, anxiety, and sadness. Add ulcerative colitis, a kind of inflammatory bowel disease (IBD) characterized by chronic inflammation of the large intestine, to this increasing list.

The intestines of mice fed a diet high in soybean oil for up to 24 weeks in the lab was investigated by researchers at the University of California, Riverside. Beneficial bacteria were discovered to be reduced, while dangerous bacteria (particularly, adherent invasive Escherichia coli) were found to be increased – circumstances that can lead to colitis.

Soybean oil is the most widely used edible oil in the United States, and it is becoming more popular in other nations, particularly Brazil, China, and India. Soybean oil was produced as a byproduct of the increasing trend in growth in the United States in the 1970s for use as animal feed. Soybeans, a good source of protein, are simple and inexpensive to raise.

“Our work challenges the decades-old thinking that many chronic diseases stem from the consumption of excess saturated fats from animal products, and that, conversely, unsaturated fats from plants are necessarily more healthful,” said Poonamjot Deol, an assistant professional researcher in the Department of Microbiology and Plant Pathology and a co-corresponding author on the paper published July 3 in Gut Microbes, an open access journal.

Deol noted that the biggest danger is linoleic acid in soybean oil.

“While our bodies need 1-2% of linoleic acid daily, based on the paleodiet, Americans today are getting 8-10% of their energy from linoleic acid daily, most of it from soybean oil,” she said. “Excessive linoleic acid negatively affects the gut microbiome.”

Deol and her colleagues discovered that a high-soybean-oil diet promotes the growth of adherent invasive E. coli in the gut. To meet its nutritional needs, this bacterium uses linoleic acid as a carbon source. Furthermore, numerous helpful bacteria in the stomach are unable to survive linoleic acid and die, resulting in the growth of dangerous bacteria. In humans, adherent invasive E. coli has been linked to IBD.

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

The barrier function of the intestinal epithelium is crucial for gut health; when it is compromised, it can result in increased permeability or leakiness. Toxins can then leak into the circulation from the stomach, increasing the risk of infections and chronic inflammatory disorders like colitis. The researchers suggest that the rise in IBD is related to the rise in soybean oil intake in the United States.

Toxicologist Frances M. Sladek, a cell biology professor and co-corresponding author on the study, recalls how saturated fats were related to heart disease in the late 1950s.

“Since studies showed that saturated fats can be unhealthy, it was assumed that all unsaturated fats are healthy,” she said. “But there are different types of unsaturated fats, some of which are healthful. For example, the unsaturated fat fish oil is well known to have many beneficial health effects. People therefore assumed that soybean oil is perfectly safe and healthier to consume than other types of oils, without actually doing a direct comparison as we have done.”

Linoleic acid, according to Sladek, is an essential fatty acid. The soybean oil employed by the researchers in their studies contained 19% linoleic acid. To keep the heart healthy, the American Heart Association recommends getting 5 to 10% of your daily calories from omega-6 polyunsaturated fatty acids like linoleic acid. Many seed oils, such as safflower and sunflower, contain linoleic acid. Animal fat is another option.

“Every animal has to get linoleic acid from the diet,” Sladek said. “No animal can make it. A small amount of it is needed by the body. But just because something is needed does not mean a lot of it is good for you. Several membranes in the body, in the brain, for example, require linoleic acid for the cells to function properly. If all we ate was saturated fats, our cell membranes would become too rigid and not function properly. Future studies are needed to determine the tipping point for how much daily linoleic acid consumption is safe.”

According to Sladek and Deol, olive oil is a healthier oil to eat because it contains less linoleic acid.

“Olive oil, the basis of the Mediterranean diet, is considered to be very healthy; it produces less obesity and we have now found that, unlike soybean oil, it does not increase the susceptibility of mice to colitis,” Sladek said.

James Borneman, a co-corresponding author on the paper and a professor of microbiology and plant pathology at UCR, is a specialist in the gut microbiota. He has worked on research projects at UCR with numerous organizations, including studies into how gut microorganisms inhibit obese people from reducing weight. He collaborated with Deol and Sladek on the current work to evaluate the intestinal microorganisms of mice fed a high soybean oil diet.

“Adherent invasive E. coli contributes to IBD in humans, and the fact that we find this E. coli in these mice is concerning,” he said. “Sometimes, it can be unclear how research done in mice translates to humans, but in this study it is fairly clear.”

The researchers were also shocked to discover that mice fed a high soybean oil diet had lower levels of endocannabinoids in their stomach, which are cannabis-like chemicals produced naturally by the body to regulate a wide range of physiological activities. At the same time, oxylipins, which are oxygenated polyunsaturated fatty acids that regulate inflammation, increased in the stomach.

“We previously found that oxylipins in the liver correlate with obesity,” Deol said. “Some oxylipins have also been found to be bioactive in colitis studies. The bottom line of our current study is that a soybean oil-enriched diet similar to the current American diet causes oxylipin levels to increase in the gut and endocannabinoid levels to decrease, which is consistent with IBD in humans.”

Most processed foods in the United States contain soybean oil, which may explain why many Americans consume more linoleic acid than is advised. Furthermore, because soybean oil is relatively inexpensive, it is used in the majority of eateries in the United States.

“Try to stay away from processed foods,” Sladek advised. “When you buy oil, make sure you read the nutrition facts label. Air fryers are a good option because they use very little oil.”

The researchers cook with and eat salads with olive oil. They also mentioned coconut oil and avocado oil as healthy cooking oils. They warned that corn oil contains the same amount of linoleic acid as soybean oil.

“We recommend keeping track of the soybean oil in your diet to make sure you are not consuming excessive linoleic acid,” Deol said. “That is our take-home message.”

Source Link