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By Mark Messina, PhD, MS
The U.S. Food Allergen Labeling & Consumer Protection Act (FALCPA) mandates labeling of all ingredients derived from commonly allergenic foods. In the United States, eight foods have been identified as the most frequent human food allergens, accounting for 90 percent of food allergies. These foods are milk, eggs, fish, crustacea, wheat, peanuts, tree nuts and soy.1,2 However, these foods are not equally allergenic—in fact, soy protein allergies are relatively uncommon.3 Being allergic to soy protein is much less common than being allergic to milk or peanuts.4,5
Importantly, the FALCPA exempts highly refined oils from these labeling provisions because highly refined soybean, peanut and sunflower seed oils have been clinically documented to be safe for consumption by individuals allergic to the source food.6-9Soy is viewed similarly in Europe, where soy protein is classified as one of the 14 most common foods that induce allergic reactions, yet fully refined soybean oil is exempt from labeling.10
The process of commercially refining soybean oil involves extraction with hot solvents, bleaching and deodorization, which serve to eliminate almost all soy protein (and thus allergens) from the oil.11 However, it is extremely difficult to quantify the protein content of oil. Attempts to do so indicate that crude oils contain about 100-300 mg/kg, whereas fully refined oils contain at least 100 times less.11 This difference explains the lack of reaction observed in response to ingesting highly refined oils, unlike ingesting unrefined or partially refined culinary oils, which have been found to elicit allergic reactions in sensitized individuals.12 While highly refined soybean oil does contain residual soy protein, the residue levels are extremely low—too low to elicit an allergic response in nearly all cases.11,13-15 Analytical data from Rigby et al.16on cumulative threshold doses for soy protein suggest that even the most sensitive individuals would need to consume at least 50g of highly refined oil to experience subjective symptoms.16
There have been a few cases where soybean oil elicited an allergic response, but these instances followed intravenous infusion of an emulsion containing soybean oil, which seems far removed from typical consumption.14,17,18 There is also one unusual case of a possible soy oil-induced allergy after an infant was fed exclusively on an amino acid-based formula containing a soybean oil-based component.19 The circumstances of exposure in this exceptional case are unusual and the association with the soybean oil component of the formula was somewhat speculative.
In addition to the clinical studies cited here showing that highly refined soybean does not elicit an allergic response, circumstantial evidence supporting the clinical results comes from the work of the Swedish National Food Administration. Since 1994, this group has been recording and investigating all cases of fatal and severe reactions to foods.20,21 While soy protein featured in about 25 percent of the reported cases (compared to ~33 percent for peanuts), none implicated soybean oil, or a product containing soybean oil as the only source of soy.
Mark Messina, PhD, MS, is the co-owner of Nutrition Matters, Inc., a nutrition consulting company, and is an adjunct professor at Loma Linda University. His research focuses on the health effects of soyfoods and soybean components. He is chairman of The Soy Connection Editorial Board and executive director of the Soy Nutrition Institute.
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