Soybean oil accounts for more than 90 percent of all the seed oil production in the United States and genetically modified (GM) soybean oil, obviously made from seeds of GM soybean plants, was recently introduced into the food supply with the benefit that it is healthier than conventional soybean oil.

Is it true?

It is true, at least in the way all food marketing, including conventional and organic, is done. Soybean oil is actually unhealthy and GMO soybean oil is identical to soybean oil made from a conventional or an organic soybean - overused, it leads to obesity, diabetes and fatty liver - but GMO soybean oil is superior in that it does not cause insulin resistance, the inability to efficiently use the hormone insulin. Vegetable oils were once thought to be the healthy alternative to animal fat, and were hydrogenated to increase their shelf-life and temperature stability. The hydrogenation, however, generated trans fats - which then became implicated in various health problems. Soybean oil is the most common vegetable oil used in the United States and it contains about 55 percent linoleic acid, a polyunsaturated fat. 

"Our previous results on mice showed that replacing some of the fat in a diet high in saturated fats from coconut oil with soybean oil - to achieve a level common in the American diet - causes significantly more weight gain, adiposity, diabetes and insulin resistance than in mice fed just the high-fat coconut oil diet," said senior investigator Frances Sladek, a professor of cell biology and neuroscience at UC Riverside.

To determine whether linoleic acid was responsible for the metabolic effects of soybean oil, the researchers designed a parallel diet in which regular soybean oil was replaced, on a per gram basis, with GM soybean oil. The GM soybean oil has a fatty acid composition (low linoleic acid) similar to that of olive oil. The GM plants were developed by DuPont to reduce trans fat production, increase soybean oil shelf life and create a generally healthier cooking oil.

"The GM soybean oil has 0 grams trans fat and more of the monounsaturated fats that are considered heart healthy," Deol said. "But it had not been tested for long term metabolic effects until our current study."

Deol and the rest of the research team found to their surprise that the parallel diet containing GM soybean oil induced weight gain and fatty liver essentially identical to that of a diet with regular soybean oil, with the exception that the mice remained insulin sensitive and had somewhat less adipose (fat) tissue.

"These results indicate that linoleic acid may contribute to insulin resistance and adiposity but that another as yet unidentified component of the soybean oil affects the liver and overall weight gain," said Poonamjot Deol, an assistant in the Sladek lab.

In their experiments, the researchers gave four groups of mice different diets for 24 weeks. Each group was comprised of 12 mice. The control group received a low-fat diet (5 percent of daily calories from fat). The other groups received a diet with 40 percent of daily calories from fat, an amount common in the American diet. One diet was high in saturated fat from coconut oil, and one had 41 percent of the saturated fat replaced with regular soybean oil. The fourth group had 41 percent of the saturated fat replaced with the GM soybean oil. The body weights, food intake, glucose tolerance and insulin sensitivity of all the mice were tracked.

What the researchers found was that mice fed a diet with either of the soybean oils had worse fatty liver, glucose intolerance and obesity than the group that got all their fat from coconut oil. But the mice whose diet included the GM soybean oil had less fat tissue than the animals that ingested regular soybean oil. These mice weighed about 30 percent more than the controls that ate a low-fat diet, while the group on the diet containing regular soybean oil weighed 38 percent more than controls. The mice on the diet that was primarily coconut oil weighed only about 13 percent more than controls. Unlike the diet with regular soybean oil, the diet with the new GM soybean oil did not lead to insulin resistance.

The take home message: GMO soybean oil is better than regular or organic soybean oil, but use olive oil instead. However, olive oil is one of the more corrupt businesses around and has been for ages, so make sure the olive oil you are buying is actually olive oil.

Sladek and Deol were joined in the research by Jane R. Evans, Antonia Rizo and Cynthia Perez at UCR; and Johannes Fahrmann, Dimitry Grapov, Jun Yang and Oliver Fiehn at UC Davis who performed extensive analysis on the liver and blood samples from these mice. The results will be presented tomorrow, March 6th, at the Endocrine Society's 97th annual meeting, currently taking place in San Diego, Calif., by Deol. The research was supported by a UCR Collaborative Seed Grant as well as grants from the UCR Agricultural Experiment Station, and the UC Davis West Coast Metabolomics Center, funded by the National Institutes of Health. Deol was supported by a training grant from the National Institute of Environmental Health Sciences.

Photo: Jeff Ruppenthal, Lancaster Online