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August 10, 2015 • Healthy Eating & Nutrition, Weight Control

Soybean Oil May be Uniquely Fattening

oil genericFructose, the notorious simple sugar molecule repeatedly singled out for its unique propensity to induce weight gain and metabolic dysfunction, may have a new rival-soybean oil. In a first-of-its-kind laboratory evaluation that really raised my eyebrows, scientists concluded, “soybean oil (a polyunsaturated fat) is more obesigenic and diabetogenic than coconut oil (a saturated fat) and fructose in mice.” For this study the researchers fed 4 groups of mice 4 diets of equal total calories and fat calories, but differing in their specific makeup. For diet 1 the fat calories came from coconut oil. For diet 2 the fat calories were half coconut oil and half soybean oil (equivalent to the amount of soybean oil Americans currently consume). Diets 3 and 4 were identical to diets 1 and 2 in fat makeup, but included added fructose (comparable to typical American intakes). The results were compelling. Mice fed diet 2  (half soybean oil, half coconut oil) developed significantly more weight gain, fat mass, glucose intolerance, insulin resistance, and fat in their livers than the mice fed diet 1 (coconut oil only). The addition of fructose to the diets also lead to metabolic dysfunction, but less severe than observed with the soybean oil diet. In addition to disturbed metabolic function, the soybean oil diet increased the activity of a slew of genes, including those involved in obesity, inflammation, diabetes, and even cancer. Taken as a whole, the results of this experiment showed that a diet high in soybean oil is worse for metabolic health than a diet high in fructose.

Unfortunately, American’s intakes of soybean oil have skyrocketed over the past 40 years, now comprising a whopping 60 percent of oils consumed in the US. Soybeans are a highly subsidized commodity crop making soybean oil one of the cheapest and thus most popular ingredients for the processed food industry. (PLOS ONE, 2015; 10 (7): e0132672 DOI: 10.1371/journal.pone.0132672)


Perhaps it is no coincidence that America’s steep increase in soybean oil consumption mirrors our twin epidemics of obesity and diabetes. Although more studies are certainly needed to make any firm conclusions, play it safe and stick to oils that have a long history of safety and documented health benefits. Click here to see my lowdown on doing your oils right!