Bean Oil Health Questioned

Conventional Soybean Oil Fattens Mice in New Study

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
Connect with Emily:
A new study suggests soybean oil may be contributing to the obesity epidemic in America. (DTN file photo)

ST. LOUIS (DTN) -- Soybean oil might be making Americans fatter and sicker, according to new research from University of California-Riverside (UCR) scientists.

They found that, despite eating the same amount of food, mice fed with a diet rich in conventional soybean oil were significantly more obese, diabetic and insulin-resistant than mice fed a diet filled with coconut oil and mice on a low-fat diet.

A small silver lining for the soybean industry emerged when a fourth set of mice were fed with soybean oil from Plenish, DuPont Pioneer's genetically engineered high-oleic soybeans. Plenish-fed mice fared better overall. The rodents still plumped up more than mice on a low-fat diet, but they did not become resistant to insulin and weighed 8% less than their colleagues fed conventional soybean oil.

The research was led by Frances Sladek, a UCR professor of cell biology and a toxicologist, and Poonamjot Deol, an assistant project scientist. The initial university press release on Sladek's study prompted so much media attention that the university published an additional in-depth interview with her, clarifying the purpose and conclusions of her research.

Sladek's research goal was to evaluate what effect linoleic acid -- a polyunsaturated fatty acid in conventional soybean oil -- might have on human health, she explained in the university interview. She tried to mimic the average American's rising consumption of soybean oil (and thus linoleic acid) in her trial.

Soybean oil "has increased 1,000-fold, more than corn oil, fructose, animal, chicken or any other single item" in American diets, she pointed out. "As a consequence of the increased consumption of soybean oil, Americans are consuming much more linoleic acid, a polyunsaturated fatty acid (PUFA). We wanted to see if high levels of soybean oil (and hence [linoleic acid]) in the diet could cause obesity and diabetes."

Sladek added Plenish for the study because it was engineered to produce much lower levels of linoleic acid, which made it the perfect foil for traditional soybean oil.

The overall picture for soybean oil was grim, despite Plenish's low-linoleic acid oil performing better, she noted.

"Soybean oil may contribute to obesity and diabetes," she said, adding later that "... both conventional and Plenish soybean oil appear to be less healthy in terms of obesity and diabetes than coconut oil."

P[L1] D[0x0] M[300x250] OOP[F] ADUNIT[] T[]

Pioneer is taking the results as a positive comment on their new product, said Susan Knowlton, a senior research manager for the company and the technical lead on the Plenish commercialization team. "The study is not yet published, so I can't really comment on it in too much depth," she told DTN. "But from what I've seen, it was a positive response [for Plenish]. It's hard to say we haven't improved, with less fat deposition and the mice retaining their sensitivity to insulin."

While the study is interesting to the company, it doesn't speak to the original purpose of Plenish soybeans, Knowlton added.

"We created Plenish not as replacement for traditional soybean oil but as a replacement for partially hydrogenated soybean oil," she explained.

Partially-hydrogenated soybean oil is used by restaurant and food manufacturers for its textural properties. However, hydrogenation produces trans-fats, which the FDA is in the process of phasing out of the food industry. Thanks to genetic tweaking, Plenish oil does not require hydrogenation, which makes it a healthier alternative for partially-hydrogenated soybean oils, Knowlton explained.

While Sladek's study supports the view that coconut and olive oil are likely our healthiest food oil options, soybeans shouldn't be written off, she said.

"Soybeans per se are not unhealthy," she said. "They are a great source of protein and isoflavones and they are easy to grow." That last point is key, since global agriculture so far has proven incapable of producing enough olive and coconut oil to feed the demand for vegetable oil, she added.

A final takeaway from the study is the promise of genetic engineering in the future of healthier foods, Sladek said.

"GM Plenish seems to have fewer negative health effects, indicating that genetic engineering can introduce beneficial properties into a crop," she pointed out.

The American Soybean Association (ASA) and the United Soybean Board (USB) declined to comment directly on Sladek's study, but USB stressed the healthy aspects of soybean oil in a statement issued to DTN.

"Soybean oil is low in saturated fat, contains no trans-fat, and is high in poly- and monounsaturated fats. It's also the principal source of omega-3 fatty acids in the U.S. diet, and the primary commercial source of vitamin E," the statement read. "According to recommendations of the American Heart Association for good health, the majority of the fats that you eat should be monounsaturated or polyunsaturated. Eat foods containing monounsaturated fats and/or polyunsaturated fats instead of foods that contain saturated fats and/or trans-fats. This recommendation is the opposite of the study's suggested results."

The USB directed DTN to Kevin Fritsche, a professor of nutrition at the University of Missouri, who expressed concerns about the study's conclusions.

Specifically, Fritsche questioned Sladek's decision to use coconut oil as a control group against soybean oil, based solely on its low-linoleic properties.

"It's been well documented for more than a decade that when you feed animals or people coconut oil, which is an unusual fat source because it is rich in medium-chain-length triglycerides, it causes weight loss," he told DTN. "It causes an increase in energy expenditure and it causes less efficient food conversion, so calories don't get stored as fat as much."

Because she used a weight-loss-causing oil as her control group, Sladek's conclusions about soybean oil were not sound, he maintained. "She should have selected lard or olive oil as her control fat for this study, and if she had, it is likely that her conclusions would have been quite different," he said.

Fritsche also cautioned against converting results from mice studies into wholesale human health conclusions. "Mice are not people, and you have to be aware of the shortcomings and limitations of doing studies on them and extrapolating the results to humans," he said. Chief among those limitations is getting the diets of mice to truly reflect the complex nature of human diets. Unlike the mice in Sladek's study, few humans get all their fat from a single source like vegetable oil, he pointed out.

For more information on Sladek's study, see this UCR news release: http://bit.ly/…, and Sladek's UCR interview here: http://bit.ly/….

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(PS/AG/CZ)

P[L2] D[728x90] M[320x50] OOP[F] ADUNIT[] T[]
P[R1] D[300x250] M[300x250] OOP[F] ADUNIT[] T[]
P[R2] D[300x250] M[320x50] OOP[F] ADUNIT[] T[]
DIM[1x3] LBL[] SEL[] IDX[] TMPL[standalone] T[]
P[R3] D[300x250] M[0x0] OOP[F] ADUNIT[] T[]

Emily Unglesbee