UC Riverside’s Frances Sladek and Poonamjot Deol explain research in which they compared a genetically modified soybean oil to conventional soybean oil
The University of California, Riverside news release dated March 5, 2015 announced findings, presented at the recent annual Endocrine Society meeting, on the health effects of a genetically modified soybean oil (Plenish). The news release generated much interest on the web. The issue is complex, and researchers Frances Sladek, a professor of cell biology and neuroscience, and Poonamjot Deol, an assistant project scientist, answer questions below and in the video above to provide additional explanation of the research they undertook.
Q. What was the original motivation of your study?
A. A research paper published in 2011 showed that the component in the American diet that had changed the most in the past century is soybean oil. It has increased 1000-fold, more than corn oil, fructose, animal, chicken or any other single item. 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 LA) in the diet could cause obesity and diabetes.
Q. Can you explain the design of your experiment?
A. We had 4 diets for mice. One was a low fat/high fiber diet that mice are normally fed in the vivarium. The other 3 diets had 40 percent fat, which is close to what Americans currently consume. In one diet we used primarily coconut oil, which consists of saturated fat. (There was a small amount of soybean oil to provide LA, an essential fatty acid.) In another diet we removed about ½ of the coconut oil and replaced it with regular soybean oil to give roughly the amount of soybean oil Americans currently consume. We prepared the fourth diet in a similar fashion to the third diet but used a new genetically modified soybean oil from DuPont that has low levels of LA. We fed mice the diets for 24 weeks and tracked their body weight and measured glucose levels and sensitivity to insulin. We also measured the amount of fat they accumulated and looked at their livers and measured all the metabolites in their liver and blood.
Q. What did you find?
A. The mice fed the soybean oil diet became much more obese, diabetic and insulin resistant than the mice fed the coconut oil diet even though they had similar food intake. They also had large lipid droplets in their liver and ballooning, a sign of liver injury. The mice that were fed the diet with the Plenish soybean oil also gained more weight than the mice fed a diet made from coconut oil, but a little less than the regular soybean oil diet. They were glucose intolerant and had similar effects in the liver compared to the regular soybean oil but they were not insulin resistant. Insulin resistance is a feature of diabetes that is particularly problematic.
Q. Why coconut oil?
A. We had to use some source of fat to control for total calories, and fat, in the diet. Coconut oil is one of the few oils that is naturally low in LA and other PUFA. We could not use animal lard as farm animals in the U.S. are currently being fed large amounts of soybean meal and hence their fat may already have high levels of LA.
Q. So, the soybean oils with unsaturated fats were less healthy than the coconut oil with the saturated fat?
A. Yes, that is correct, in terms of obesity, diabetes and liver effects.
Q. But saturated fats are supposed to be unhealthy and unsaturated fats healthy?
A. That is the dogma based on large epidemiological studies from the 1950s and 1960s that showed the risk for heart disease correlated with the consumption of animal fat, which is largely saturated fat. Since saturated fat was found to be unhealthy, it was automatically assumed that unsaturated fat was healthy although it was never really properly tested in long-term studies until recently. The type of saturated fat in coconut oil is not exactly the same as the saturated fat in animal lard. There are many different types of saturated (and unsaturated) fat.
Q. So did you examine cardiovascular effects in the soybean oil diet?
A. We did not look at heart disease per se. We did, however, find a decrease in cholesterol in the livers of mice fed the soybean oil, although there was no decrease of cholesterol in the blood.
Q. Why did you decide to test the genetically modified soybean oil Plenish?
A. Plenish is genetically engineered by DuPont to have lower amounts of LA so that it does not generate trans-fats upon heating and has a longer shelf life. In order to do that they blocked the enzyme that converted oleic acid (a mono unsaturated fat) into LA, and hence called it “high oleic acid soybean oil.” Thus, Plenish was the perfect control to see if LA was a driver of the obesity and diabetes we saw in regular soybean oil.
Q. So your results suggest that the genetic modification introduced by DuPont might actually be a good one?
A. Yes. It should be noted that DuPont did not set out to purposefully make a healthier soybean oil because at the time no one considered soybean oil as being unhealthy.
Q. Why are we just finding out now that soybean oil is unhealthy?
A. The main reason is that no one ever examined diets with the high levels of soybean oil until recently. Indeed, a couple other groups have observed similar effects to ours with a high soybean oil diet although as far as we know no one else has compared regular soybean oil to Plenish.
Q. When we talk of genetically modified crops we are usually referring to other types of modifications, such as those made by Monsanto to create plants resistant to the herbicide RoundUp. Does that genetic modification come into play in your study?
A. Both the conventional soybean oil we tested and Plenish are from soybeans that are genetically modified to be resistant to RoundUp. In fact more than 90 percent of all soybeans in this country are genetically modified to be resistant to RoundUp so it is very difficult to find soybean oil that does not come from a genetically modified plant.
Q. Have you compared either of the GM soybean oils to organic soybean oil?
A. No. At this point we have no reason to think that the RoundUp resistant feature is relevant to the effects we observe. Also, the problem is that the organic soybean oil is likely to be from a different strain of soybean.
Q. What about olive oil?
A. The fatty acid composition of Plenish is much more similar to olive oil than it is to regular soybean oil. DuPont advertises Plenish as being “heart healthy” like olive oil. Olive oil is certainly one of the healthiest of all oils – it is the basis of the Mediterranean diet, along with lots of fish, fruits and nuts. However, there are components in all plant oils other than fatty acids so we anticipate that olive oil will not give the same results as Plenish.
Q. If all the experts agree that olive oil is the healthiest of all oils, why doesn’t everyone just eat olive oil? Or coconut oil?
A. There is not enough olive oil to feed everyone in the world. 40 million tons of soybean oil were produced worldwide in 2007 while Spain, the major producer of olive oil, produces only about 1 million tons of olive oil per year. It takes 20 years for olive trees to start producing olives while with soybeans you get a crop in the first year. There is a similar issue with coconut oil. Currently about 3.6 million tons of coconut oil are produced worldwide according to the USDA.
Q. Are soybeans good or bad for you?
A. Soybeans per se are not unhealthy. They are a great source of protein and isoflavones and they are easy to grow.
Q. What is the take home message?
A. Soybean oil may contribute to obesity and diabetes and the GM Plenish seems to have fewer negative health effects, indicating that genetic engineering can introduce beneficial properties into a crop. But both conventional and Plenish soybean oil appear to be less healthy in terms of obesity and diabetes than coconut oil.
Q. Did you receive any funding from DuPont? Did they have any role in designing the experiments or interpreting the results?
A. No, on both accounts. DuPont provided us with the Plenish oil initially in August 2013 as it was not yet on the market. They learned about our results on the same day as everyone else at the press conference at the Endocrine Society meeting.
Q. What were your sources of funding?
A. The University of California Riverside and National Institutes of Health funds via the West Coast Metabolomics Center at UC Davis. Poonam Deol was supported by a training grant from the National Institute of Environmental Health Science.
Source: UC Riverside