A study shows that soybean oil, the most consumed in the United States, could affect the nervous system.
Eating soybean oil has already been linked to obesity and diabetes . Now, new research from scientists at the University of California Riverside shows that soybean oil may also adversely affect certain neurological conditions .
The study also disproves advertising claims that so-called Plenish soy is healthier. This a GMO soybean oil, released by DuPont in 2014, designed to have low levels of linoleic acid and generates less trans fat during cooking.
Soybean oil is used for fast food frying, added to packaged and ultra-processed foods, and served as livestock feed. It is the most widely produced and consumed edible oil in the United States, according to the United States Department of Agriculture.
A new study, published in the journal Endocrinology, compared mice fed three different high-fat diets: "conventional" soybean oil (ie, high in linoleic acid), Plenish soybean oil, and coconut oil. There was also an additional low-fat control diet.
The researchers do not define "conventional" soybean oil in their paper, but it is almost certainly derived from RoundupReady soybeans, since about 94% of the soybean crop in the United States is of this type.
The researchers performed a transcriptomic analysis, a type of molecular analysis that analyzes gene expression in the four groups of animals being tested.
The researchers found pronounced effects in the hypothalamus, where a number of critical neural processes take place.
The results showed significant differences between the groups fed with coconut oil and low-fat diets; with the group of animals exposed to diets based on soybean oil.
The researchers found that, in the two groups of animals fed soy-based diets, there was significant dysregulation of more than 100 hypothalamic genes, including those involved in neurochemical and neuroendocrine pathways and metabolic and neurological disorders.
"The hypothalamus regulates body weight, maintains body temperature, is essential for reproduction and physical growth, and in responding to stress," said Margarita Curras-Collazo, author of the article.
The team determined that several genes in mice fed soybean oil were not working properly. One of these genes produces the so-called "love" hormone, oxytocin. In mice fed both types of soybean oil, oxytocin levels in the hypothalamus decreased.
The research team believes their discovery could have ramifications not only for energy metabolism, but also for proper brain function and diseases such as autism or Parkinson's disease. However, it is important to note that no specific tests were done to show that soybean oil causes these diseases.
A separate study by UCR researchers found in 2015 that soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice . Then, in a 2017 study, the same group found that soybean oil genetically modified to have low linoleic acid content, induces less obesity and insulin resistance .
Regarding the new study on brain effects, the research team has yet to identify 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 transgenic oil with a low content of linoleic acid also produced genetic alterations; 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.
"If there is a message that I want people to take, it is this: you need to reduce your consumption of soybean oil," said Deol, a co-author of the article.
The research team clarifies that the findings of this research only apply to soybean oil, not other soy products, or other vegetable oils.Looking at the big picture, the new study has a lesson for those who are excited about GM foods, manipulated to be better nutritionally: a healthy nutritional profile must be defined holistically, not just looking at one or a few nutrients. It is counterproductive to design a food to be heart healthy if it is likely to damage brain function.
 Costa CA, Carlos AS, dos Santos Ade S, Monteiro AM, Moura EG, Nascimento-Saba CC. Abdominal adiposity, insulin and bone quality in young male rats fed a high-fat diet containing soybean or canola oil. Clinics 2011; 66 (10): 1811-1816.
Deol P, Fahrmann J, Yang J, Evans JR, Rizo A, Grapov D, Salemi M, Wanichthanarak K, Fiehn O, Phinney B, Hammock BD, Sladek FM. Omega-6 and omega-3 oxylipins are implicated in soybean oil-induced obesity in mice. Sci. Rep. 2017; 7 (1): 12488.
Deol P, Evans JR, Dhahbi J, Chellappa K, Han DS, Spindler S, Sladek FM. Soybean oil is more obesogenic and diabetogenic than coconut oil and fructose in mouse: potential role for the liver. PLoSOne 2015; 10 (7): e0132672. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0132672
Mamounis KJ, Yasrebi A, Roepke TA. Linoleic acid causes greater weight gain than saturated fat without hypothalamic inflammation in the male mouse. J. Nutr. Biochem. 2017; 40: 122-131.
 Deol P et al. Dysregulation of hypothalamic gene expression and the oxytocinergic system by soybean oil diets in male mice. Endocrinology 2020: bqz044. https://doi.org/10.1210/endocr/bqz044
 Deol P et al. Deol P, Evans JR, Dhahbi J, Chellappa K, Han DS, Spindler S, Sladek FM. PLoS One 2015; 10 (7): e0132672. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0132672
 Deol P, Fahrmann J, Yang J, Evans JR, Rizo A, Grapov D, Salemi M, Wanichthanarak K, Fiehn O, Phinney B, Hammock BD, Sladek FM. 2017; 7 (1): 12488.
The complete new study (in English) is found here: PoonamjotDeol et al (2020). Dysregulation of hypothalamic gene expression and the oxytocinergic system by soybean oil diets in male mice.) Endocrinology.doi.org/10.1210/endocr/bqz044 https://academic.oup.com/endo/article/161/2/bqz044/5698148