Soybean oil linked to metabolic and neurological changes in mice

Soybean oil not only leads to obesity and diabetes, but could also affect neurological conditions like autism, Alzheimer's disease, anxiety, and depression, according to a new study by researchers at the University of California Riverside, published in the journal Endocrinology.

Used for fast food frying, added to packaged foods, and fed to livestock, soybean oil is by far the most widely produced and consumed edible oil in the U.S., according to the U.S. Department of Agriculture. 

The study compared mice fed three different diets high in fat: soybean oil, soybean oil modified to be low in linoleic acid, and coconut oil.

While previous research showed soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice, and if soybean oil is engineered to be low in linoleic acid, it induces less obesity and insulin resistance, in the new study researchers did not find any difference between the modified and unmodified soybean oil's effects on the brain. Specifically, the scientists found pronounced effects of the oil on the hypothalamus, where several critical processes take place.

The team determined several genes in mice fed soybean oil were not functioning correctly. One such gene produces oxytocin. In soybean oil-fed mice, levels of oxytocin in the hypothalamus went down.

The research team discovered roughly 100 other genes also affected by the soybean oil diet. They believe this discovery could have ramifications not just for energy metabolism, but also for proper brain function and diseases such as autism or Parkinson's disease. However, it is important to note there is no proof the oil causes these diseases. Additionally, the team notes the findings only apply to soybean oil, not to other soy products or to other vegetable oils.

The research team has not yet isolated which chemicals in the oil are responsible for the changes they found in the hypothalamus. But they have ruled out two candidates. It is not linoleic acid, since the modified oil also produced genetic disruptions; nor is it stigmasterol, a cholesterol-like chemical found naturally in soybean oil. Identifying the compounds responsible for the negative effects is an important area for the team's future research.