Soybean oil — a vegetable oil made from soybean seeds — is one of the most popular types of oils consumed in the U.S., often found in fast food, packaged foods and livestock feed. In a new study out of the University of California (UC) Riverside, researchers reported a link between soybean oil and genetic changes in the brains of mice.
In recent years, dietitians and researchers have examined various types of high-fat oils for their impact on human health, primarily heart health and obesity. All oils, such as peanut, soybean, sesame, olive, avocado or canola oil, have varying levels of saturated, monounsaturated and polyunsaturated fatty acids.
Olive oil, for example, is high in fat — but the “good” kind, known as unsaturated fats. Olive oil is considered a pillar of the Mediterranean diet, which is touted for its benefits in fighting cardiovascular disease and even Alzheimer’s.
The same researchers of the new study examined soybean oil in 2015 for its potential contribution to obesity and diabetes. Soybean oil’s consumption has also increased significantly in recent decades in the U.S., making it ubiquitous in the American diet, found in salad dressings, margarines and fried food.
But among other experts, it’s considered heart-healthy, and in 2017 the FDA gave it a qualified health claim of being as good for you as other high-oleic oils like olive oil.
The Brain on Soybean Oil
In the latest study, the researchers tested the effects of soybean oil on mice, compared to the effects of low linoleic acid soybean oil and coconut oil. Both types of soybean oil appeared to show the same impact on the brain. That was mostly seen as a change in the hypothalamus, a brain region that’s associated with a number of functions like body weight, metabolism, body temperature, reproduction and stress response.
The researchers concluded that certain genes in the mice that were given soybean oil weren’t operating properly, identifying about 100 of them. They noticed one particular gene that produces oxytocin, also known as the “love hormone,” seemed to be impaired in mice who ate soybean oil. Among those mice, oxytocin levels were lower than normal.
When the researchers tested coconut oil on the mice, they found it didn’t produce as many gene changes in the hypothalamus as the soybean oil did. Considering soybean oil is a very present aspect of the American diet, the authors argue their findings could have some public health ramifications.
There is, however, a catch — as there often is in studies done in mice or animals. The researchers note that while the results appear to pinpoint soybean oil as a culprit for negative brain changes, a firm conclusion cannot yet be drawn. Not much can be inferred until the same test is done in humans and produces similar results.
The Deal With Soy Products
That being said, “Do not throw out your tofu, soy milk, edamame or soy sauce,” Frances Sladek, a UC Riverside toxicologist and professor of cell biology, said in a news release.
Indeed, though soybean oil comes from soybean seeds, that doesn’t mean all products containing soy are bad for your health.
“Many soy products only contain small amounts of the oil, and large amounts of healthful compounds such as essential fatty acids and proteins,” Sladek continued.
This also means, however, that you may want to be careful about how much soybean oil you’re eating.
“This could help design healthier dietary oils in the future,” Poonamjot Deol, an assistant project scientist and author of the study, said in the news release. “The dogma is that saturated fat is bad and unsaturated fat is good. Soybean oil is a polyunsaturated fat, but the idea that it’s good for you is just not proven.”