Americans consume about 40 percent of their calories in fat, much of it from soybean oil. To test how our soybean oil consumption may be affecting us, researchers at the University of California, Riverside, fed mice one of two diets containing that much fat.
One group of mice ate coconut oil, which is mostly a saturated fat. In diet number two, half the fat came from soybean oil, the main ingredient in vegetable oil. This diet was similar to what Americans eat. The two diets contained the same number of calories.
Mice on the high soybean oil diet — which, remember, was a stand-in for the American diet — ended up gaining almost 25 percent more weight than the coconut-oil eaters. They accumulated more fat and were more likely to develop fatty liver, diabetes, and insulin resistance, all contributors to metabolic syndrome.
It may sound odd that coconut oil, a saturated oil, would be better for you — haven’t we been told for years to avoid saturated fatty acids? Studies in the 1950s and 1960s linked eating saturated fats and heart disease, and we were told to cut back on meat and dairy products and get our fat from plants instead. But evidence is growing that coconut and palm oil, which contain a different kind of saturated oil, may actually help prevent and even treat metabolic syndrome, the authors write.
You might also be surprised to hear that soybean oil could be a bigger problem in your diet than sugar. In this study, two other sets of mice also ate about the same amount of fructose as Americans consume.
Again, the mice ate the same amount of calories in each of the diets, which allowed researchers to compare the impact of the food itself.
Mice who ate fructose gained 12 percent more weight than those on the coconut oil. But they did better than those who ate soybean 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, PhD, a professor of cell biology and neuroscience.
That doesn’t mean you should eat more sugar — but it does suggest that you should cut back on vegetable oil, which you’ll find in processed foods, margarine, salad dressings, and snacks. Corn oil is less fattening than soybean oil, though not as good as coconut oil. The team is currently testing lard and olive oil.
Should you run out and buy coconut oil? Not so fast. The benefits of coconut oil remain controversial. On the other hand, olive oil has emerged as a winner in any number of studies. For example, one large study found that consuming olive oil reduced heart disease and death in a population at high risk for heart problems. The clearest message here is to limit your consumption of soybean oil and vegetable oil.
September 10, 2015
Christopher Nystuen, MD, MBA