Soy-allergic people do not react because refined oil contains only minuscule amounts of protein, the culprit in allergic reactions, says food toxicologist Sue Hefle, who headed the research with fellow scientist Steve Taylor.
Their findings do not apply to cold- or expeller-pressed soy oil, which contains more protein and may cause reactions.
"They [allergic consumers] still need to carefully read labels, but if highly refined soy oil is the only soy ingredient, they know it's OK to eat that product," she adds.
For the study, the researchers evaluated 30 highly refined soy oils from around the world. They blended four oils containing the most protein to create a representative worldwide sample.
Collaborating physicians at US, Canadian, French and South African universities fed soy-allergic volunteers 1.5 tablespoons of soy or canola oil hidden in oatmeal.
"None of the 29 volunteers at the five test sites worldwide had a reaction - these 29 people represent a statistically significant sample of geographically and ethnically diverse populations," said the scientists.
According to Taylor, food manufacturers, regulators and farmers have all expressed interest in the study. He claims the Nebraska findings played a role in recent European Union food allergen labeling decisions as well as the US Food Allergen Labeling and Consumer Protection Act of 2004, which Congress passed to protect allergic consumers.
In March, highly refined soybean oil was among the soy components that the European Union temporarily exempted from food allergen labeling regulations slated to take effect later this year, he said.
The EU's European Food Safety Authority allowed industry groups to request exemptions if they could provide scientific evidence that a food product or ingredient does not cause allergic reactions. Industry included UNL's findings in a successful request for a three-year temporary exemption.
"The temporary exemption means the EU panel has some questions but feels comfortable that refined soy oil won't cause reactions," Hefle explained.
Last year, US regulators exempted highly refined vegetable oils derived from known allergens, such as soybeans or peanuts, from the new federal food allergen labeling law that takes effect in 2006. Nebraska's soy oil research and a similar British study on refined peanut oil provided scientific evidence for that decision, Taylor said.
As a result, ingredient labels on foods containing soy oil need not explicitly list soy oil. Instead, labels can read "soybean, canola or saffllower oil." That is significant for food makers who prefer using whatever oil is plentiful and inexpensive. If soy oil had to be specifically labeled, some processors might switch to other oils, he said.
Scientists long have known protein's role in allergic reactions. Taylor's early, smaller studies of soy and peanut oils in the 1980s at the University of Wisconsin indicated refined oil wasn't a problem, but scientists needed a comprehensive study of soy oils worldwide to be sure.
"We fed them more oil than anyone is likely to consume in one sitting in the real world," Hefle said. "If they didn't react to this worse-case scenario, they're not going to react."
IANR scientists now are working to identify precisely how much protein from soy, peanut and shrimp triggers an allergic reaction. Knowing these reaction thresholds should help expand safe food choices for allergic consumers.
The United Soybean Board and food companies helped fund the soy oil research, conducted in cooperation with IANR's Agricultural Research Division.