A new comprehensive analysis of the scientific literature, published in the journal Nutrition, concludes that soybean oil lowers risk of coronary heart disease without causing any undesirable effects as some critics have claimed. That is certainly good news for Americans since soybean oil accounts for more than 7% of the total caloric intake in the United States. Soybean oil (commonly marketed as vegetable oil) is the leading edible oil globally and in the U.S., and is found in a wide array of commonly consumed products.
“We reviewed the clinical and epidemiologic literature to determine the effects of soybean oil on cholesterol levels, inflammation, and oxidation,” said Kristina Petersen, PhD, assistant professor, Texas Tech University, and one of the authors of the analysis. “Several lines of evidence indicate that soybean oil can positively contribute to overall health and reduce risk of coronary heart disease.”
In 2017, the U.S. Food and Drug Administration approved a health claim for soybean oil and coronary heart disease based on the ability of soybean oil to lower blood cholesterol when replacing saturated fat in the diet. However, despite the health claim, some have argued that the high polyunsaturated fat content of soybeans can cause inflammation and oxidative stress, which can increase risk of heart disease as well as other chronic diseases.
“There is a lot of misinformation about health properties of vegetable oils like soybean oil,” said Gregory Shearer, PhD, a professor at Pennsylvania State University, and one of the authors of the analysis. “This analysis should allay concerns related to inflammation; soybean oil does not cause harmful levels of inflammation.”
Soybean oil is high in omega-6 polyunsaturated fat. Historically, omega-6 fat has been viewed as being pro-inflammatory, while omega-3 polyunsaturated fat, which is found in some types of fish, is thought to inhibit inflammation. However, Shearer and his colleagues found that clinical studies consistently showed that soybean oil did not increase inflammation. Further, he and his colleagues documented that although at one time health agencies provided guidance on the optimal dietary ratio of omega-6 to omega-3 fat, this is no longer the case.
Instead, health agencies, such as the American Heart Association, discount the importance of the ratio and emphasize the importance of making sure the diet includes enough of each type of fat. Soybean oil contains both omega-6 and omega-3 fat.
The analysis also addressed the issue of oxidative stress. Polyunsaturated fat, including omega-3 polyunsaturated fat, oxidizes more quickly than saturated fat and monounsaturated fat because it contains multiple double bonds. However, the analysis found that overall, concerns about soybean oil increasing oxidative stress are not justified, certainly not to the point where the benefits of soybean oil would be outweighed.
Shearer says this analysis, which was funded by the United Soybean Board, should allay concerns people may have about soybean oil causing inflammation and oxidative stress. These findings, paired with the fact that both the FDA and the American Heart Association have cited the benefits of soybean oil, demonstrate the important role soybean oil can play in the American diet.