According to a recent study published in the journal PLOS ONE and conducted by researchers at the University of California, Riverside, a diet high in soybean oil causes more diabetes and obesity than a diet high in fructose, a sugar usually found in processed foods and soda.
For the study, the research team gave mice four different diets containing 40% fat, similar to the typical Americans diet.
In one diet, the researchers used coconut oil, and in the second diet half of the coconut oil was substituted with soybean oil, which contains primarily polyunsaturated fats. In the other two diets, the researchers added fructose. All diets had the same amount of calories. Results revealed that in comparison to mice fed with the diet high on coconut oil, those mice fed with the diet high in soybean oil diet had larger fat deposits, a fatty liver, gained weight, had diabetes and insulin resistance.
Mice fed with the diet high in fructose in the diet were found to have less metabolic effects than soybean oil. However, the diets high in fructose were found to cause an increase in prolapsed rectums, a symptom of inflammatory bowel disease (IBD) and more negative effects in the kidney.
The researchers also found that mice that were on the diet high in soybean oil gained nearly more 25% weight than those fed with the diet high in coconut oil and gained 9% more weight than the mice with the diet high in fructose. Mice fed with the diet high in fructose gained more 12% of weight than the mice fed with the diet high in coconut oil.
“This was a major surprise for us — that soybean oil is causing more obesity and diabetes than fructose — especially when you see headlines everyday about the potential role of sugar consumption in the current obesity epidemic,” said Poonamjot Deol, the assistant project scientist who directed the project in the lab of Frances M. Sladek, a professor of cell biology and neuroscience.
US guidelines encourage people to reduce their daily consumption of saturated fats, and increase their daily consumption of polyunsaturated fatty acids found in soybean oil. This led to an increase in the consumption of soybean oil, found in margarines, snack foods, salad dressings and processed foods. The increase in soybean oil consumption in the US mirrors the rise in obesity rates.
In the US, fructose consumption has also increased, from about 37 grams daily in 1977 to 49 grams daily in 2004.
This study is the first looking at the effects of saturated fat, unsaturated fat and fructose on diabetes, obesity, insulin resistance and nonalcoholic fatty liver disease, which with hypertension and heart disease represent Metabolic Syndrome.
The researchers also examined gene expression changes and the levels of metabolites present in the livers of mice that were fed with these four different diets. Results showed that mice fed with the diet high in soybean oil had had affected expression of the genes responsible for metabolize drugs and other external compounds that enter the body. This indicates that a diet high in soybean oil may affect one’s response to drugs and environmental toxicants, this is the results are in humans are the same as the ones found in mice.
The research team also conducted a study with corn oil, with the results showing that corn oil triggered more obesity compared to coconut oil, but not as much as soybean oil. The researchers are now looking at the effects of olive and lard oil.
This new study relates to previous findings of a study conducted at the UC Davis West Coast Metabolomics Center that compared regular soybean oil to a genetically modified soybean oil. The results from that study showed that the high oleic soybean oil (Plenish), is better than regular soybean oil.
The research team is now finalizing an article in which they incorporate these results with tests done with olive oil.