Soybean oil is America’s most widely produced and consumed edible oil by far, says the U.S. Department of Agriculture. It is used for fast food frying, fed to livestock, and added to packaged foods. Yet, it likely isn’t healthy for humans as it certainly isn’t healthy for mice.
A UC Riverside research team has been conducting a series of studies on soybean oil’s effects in mice. The first one was in 2015, and it found the oil induces diabetes, insulin resistance, obesity, and fatty liver disease. The next one was in 2017, and it revealed that if the soybean oil was engineered to be low in linoleic acid, it leads to less insulin resistance and obesity.
The latest of the studies might be the most frightening one of all. It shows that soybean oil could affect neurological conditions like Alzheimer’s disease, autism, anxiety, and depression because it altered the hypothalamus, a region of the brain where critical processes take place. The new study has been published in Endocrinology.
Lead author Margarita Curras-Collazo, a UCR associate professor of neuroscience, said:
The hypothalamus regulates body weight via your metabolism, maintains body temperature, is critical for reproduction and physical growth as well as your response to stress.
There was no difference in effects on the brain between the modified (low in linoleic acid) and unmodified soybean oil.
For the experiment, mice were divided into three groups, each being fed a different diet high in fat: soybean oil, modified soybean oil, and coconut oil.
They compared the effects and found that around 100 genes were affected in the mice fed a soybean oil diet. The genes were not functioning correctly. For example, the gene that produces oxytocin, the “love” hormone, became impaired because soybean oil-fed mice had lowered levels of oxytocin in the hypothalamus.
These findings suggest the oil could have ramifications for proper brain function in addition to energy metabolism.
First author Poonamjot Deol, an assistant project scientist in Sladek’s laboratory, said:
If there’s one message I want people to take away, it’s this: reduce consumption of soybean oil.
The researchers believe it could be linked to diseases such as Parkinson’s or autism, but there is no proof that soybean oil causes these diseases at this point. They also note that these results only apply to soybean oil, not to other vegetable oils or soy products.
UCR toxicologist Frances Sladek, a professor of cell biology, said:
Do not throw out your tofu, soymilk, edamame, or soy sauce. Many soy products only contain small amounts of oil and large amounts of healthful compounds such as essential fatty acids and proteins.
The teams’ future research will focus on identifying the compounds responsible for the adverse effects. They have ruled out two possibilities already: it isn’t linoleic acid because the modified oil also induced genetic disruptions in the brain, and it isn’t a cholesterol-like chemical called stigmasterol. They must pinpoint the source of the problem for the industry to solve the problem.
Deol said:
This could help design healthier dietary oils in the future.
Sladek added:
The dogma is that saturated fat is bad and unsaturated fat is good. Soybean oil is polyunsaturated fat, but the idea that it’s good for you is just not proven.
The coconut oil produced minor changes in the hypothalamic genes, and yet it contains plenty of saturated fats.
