Mouse Study: Soybean Oil May Disrupt Metabolism, Oxytocin
A new mouse study reveals that soybean oil has a pronounced effect on the hypothalamus, a region of the brain involved in metabolism, reproduction and stress response, and may even affect neurological conditions like autism, Alzheimer’s disease, anxiety, and depression.
Commonly used for fast food frying, livestock feed and packaged foods, soybean oil is by far the most widely produced and consumed edible oil in the United States, according to the U.S. Department of Agriculture.
For the study, researchers from the University of California, Riverside (UCR) compared mice who had been fed three different diets high in fat: soybean oil, soybean oil modified to be low in linoleic acid, and coconut oil.
In 2015, the same team discovered that soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice. Then in a 2017 study, they found that if soybean oil is engineered to be low in linoleic acid, it induces less obesity and insulin resistance.
However, in the new study, the researchers did not find any difference between the modified and unmodified soybean oil’s effects on the brain. Specifically, they found pronounced effects of the oil on the hypothalamus, where a number of critical processes take place.
“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,” said Dr. Margarita Curras-Collazo, a UCR associate professor of neuroscience and lead author on the study.
The findings reveal that a number of genes in mice fed soybean oil were not functioning correctly. One such gene produces the “love” hormone, oxytocin. In soybean oil-fed mice, levels of oxytocin in the hypothalamus went down.
The 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.
“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,” said Frances Sladek, a UCR toxicologist and professor of cell biology.
Indeed, coconut oil, which contains saturated fats, produced very few changes in the hypothalamic genes.
Still, it is important to note there is no proof that soybean oil causes neurological diseases. In addition, the team notes that the findings only apply to soybean oil, not to other soy products or to other vegetable oils.
“Do not throw out your tofu, soymilk, edamame, or soy sauce,”said Sladek. “Many soy products only contain small amounts of the oil, and large amounts of healthful compounds such as essential fatty acids and proteins.”
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 which compounds are responsible for the negative effects is an important area for the team’s future research.
“This could help design healthier dietary oils in the future,” said Dr. Poonamjot Deol, an assistant project scientist in Sladek’s laboratory and first author on the study. “If there’s one message I want people to take away, it’s this: reduce consumption of soybean oil.”
The study is published in the journal Endocrinology.
Pedersen, T. (2020). Mouse Study: Soybean Oil May Disrupt Metabolism, Oxytocin. Psych Central. Retrieved on August 13, 2020, from https://psychcentral.com/news/2020/01/26/mouse-study-soybean-oil-may-disrupt-metabolism-oxytocin/153679.html