Researchers at the University of California, Riverside have come out with evidence that soybean oil, the leading vegetable oil in the US food chain, may be contributing to weight gain far more than previously understood. The findings have been published in the Journal of Lipid Research.
The team of researchers observed that mice fed with high amounts of soybean oil were much heavier compared to those fed with different fats. In fact, the relationship between soybean oil consumption and obesity in mice became evident enough for the scientific community to note that soybean oil consumption leads to this condition.
However, an unexpected turn of events occurred during this experimentation process. In testing the same mice that were genetically altered, it was seen that the mice failed to exhibit this weight gain despite following the same diet that is abundant in soybean oil. It had one difference: it contained a variation in the liver protein HNF4a that controls genes for fat metabolism.
A variant of this protein is apparently different in the processing of linoleic acid, a prominent ingredient in soybean oil, and this leads to lower amounts of lipid deposition. The variant is present in humans too, but it manifests only when the human body is under stress due to illness, alcoholic-induced damage to the liver, fasting, or any other problems in metabolism.
“This may go some way towards explaining why some individuals may gain weight more easily than others when on diets containing soybean oil,” explained Sonia Deol, biomedical scientist at the University of California Riverside and one of the authors of the study.
Why soybean oil raises questions
Consuming soybean oil in the US has increased dramatically in the past century. According to past literature published in the American Journal of Clinical Nutrition, soybean oil currently makes up about 10% of total calories in the American diet, whereas it only comprised about 2% of total calories in the American diet 100 years ago.
Although soybeans are abundant in plant protein and the oil is devoid of any cholesterol, it is when the linoleic acid, an omega-6 fatty acid, is metabolized in the body that some problems arise. Consequently, when the UCR team investigated, it was found that it decomposes into certain chemicals known as oxylipins that are linked to increased swelling and lipid deposition.
Cell biologist Frances Sladek of UCR described the implications of past findings that had indicated soybean oil caused more weight gain than other oils such as coconut oil. “What we are finding now is that this problem is not just due to the oil itself, but it’s the metabolites that are created when it enters the body that are problematic,” she added.
Because soybean oil is used extensively in processed and fast food, findings contribute to escalating concerns about the potential for the American diet to influence health in the face of extensive consumption of such food products. Even though soybean oil contains no cholesterol, the researchers reported that mice fed large amounts of it had higher-than-expected levels of cholesterol.
In a statement made by Sladek, she explained that the oil should not be demonized outright. The problem lies in the sheer quantity Americans consume, which may overwhelm metabolic pathways our bodies were never designed to handle.
