Recently introduced to the market on the premise that it's healthier than the regular stuff, genetically modified (GM) soybean oil could be only minimally better for you, say scientists at the University of California at Riverside.
The research team, who will present their study on Friday at ENDO 2015, the Endocrine Society's 97th annual meeting in San Diego, California, compared both oils effects on mice and concluded that both are perfectly unhealthy, causing obesity, diabetes and fatty liver.
The only advantage of GM soybean oil is that it doesn't reduce the body's ability to use the hormone insulin.
"While the GM soybean oil may have fewer negative metabolic consequences than regular soybean oil, it may not necessarily be as healthy as olive oil, as has been assumed by its fatty acid composition, and it is certainly less healthy than coconut oil which is primarily saturated fat," says senior investigator Frances Sladek, a professor of cell biology and neuroscience at UC Riverside.
Soybean oil contains 55% linoleic acid, a polyunsaturated fat.
Vegetable oils were once thought to be healthy because they are naturally high in unsaturated fat.
In that era, they were hydrogenated to increase shelf life and their susceptibility to extreme temperatures, yet this process generated trans fats that are widely known-even feared-for their unhealthy effects.
GM soybean oil is thought to be healthier because it's low in linoleic acid, has zero trans fat and in general, its fatty acid composition is similar to that of olive oil because it contains monounsaturated fat.
Yet it caused weight gain and fatty liver just like its unmodified counterpart.
In the study, four groups of 12 mice were fed different diets for 24 weeks.
The control group received a low-fat diet, in which only 5% of their daily caloric intake came from fat.
All three of the other groups were fed a diet in which 40% of calories per day came from fat, which are common proportions in the American diet.
Predominant oils in the groups included coconut oil, regular soybean oil and GM soybean oil.
The coconut oil group had the best outcome of the three test groups, for both the soybean oil groups had worse fatty liver, glucose intolerance and obesity levels.
The GM soybean oil mouse group was 30% heavier than the control group whereas the regular soybean oil group was 38% heavier than those in the control group.
Mice on the GM soybean oil-based diet had less fat tissue than those who were fed the diet based on regular soybean oil, although the results indicate that neither one should be considered a top choice.