SAN DIEGO — A new soybean oil genetically modified to be healthier than conventional soybean oil may cause obesity, prediabetes and fatty liver in a manner nearly identical to that of regular soybean oil, according to a new study presented at ENDO 2015. 

Senior investigator Frances Sladek, PhD, who is a professor of cell biology at the University of California, Riverside (UCR), said the recently introduced high-oleic soybean oil, sold as Plenish (DuPont), until now had not been tested for any lasting metabolic effects

While genetic modification of crops can introduce new beneficial traits into existing crops, the resulting products need to be tested for long-term consequences before assumptions are made about their impact on human health, according to Dr. Sladek.

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Marketing for the new soybean oil claims it has 0 grams of unhealthy trans fats, more of the heart-healthy monounsaturated fats and a longer shelf life. The product also contains high levels of oleic acid and low levels of linoleic acid, a polyunsaturated fat. This makes it similar to the fatty acid composition of olive oil.

Traditional soybean oil, which contains about 55% linoleic acid, is the most common oil consumed in the U.S. diet, and its use has increased remarkably since the 1970’s. In a previous study, Dr. Sladek’s postdoctoral fellow Poonamjot Deol, PhD, found that mice fed soybean oil as part of a high-fat diet had higher rates of obesity, diabetes, insulin resistance and fatty liver than mice on a diet high in saturated fat from coconut oil.

Study Results

In the current study, the researchers gave four groups of mice — 12 in each group — different diets for 6 months. The control group received a low-fat diet, in which 5% of daily calories were from fat. The other groups received a diet with 40% of daily calories from fat. One diet was high in saturated fat from coconut oil, and one had 41% of the saturated fat replaced with regular soybean oil. The last group had 41% of the saturated fat replaced with the genetically modified high-oleic soybean oil.

The researchers found that mice fed a diet with either of the soybean oils had worse fatty liver, glucose intolerance and obesity than the group that received all their fat from coconut oil. However, the mice whose diet included the high-oleic soybean oil had less fat tissue than the animals that ingested regular soybean oil. These mice weighed about 30% more than the controls that ate a low-fat diet, while the group on the diet containing regular soybean oil weighed 38% more than controls.