Soy is one of the eight most common food allergens, according to the United States' Food Allergen Labeling and Consumer Protection Act. Soy lecithin is often considered hypoallergenic because it contains only a minimal amount of soy protein, which is responsible for the allergic response to soy. However, variable conditions and quality control of processing methods in the manufacture of soy lecithin contribute to trace amounts of soy protein. For sensitive individuals, these small amounts often provoke allergenic symptoms.
Processing
Lecithin is extracted during the processing of soybean oil. Heated and hydrated soybeans are cracked and separated from the hulls before being pressed into flakes. A distillation process extrudes the oil from the soybean flakes. The remaining component is made into lecithin by the addition of water and steam. Soy lecithin is used in many processed foods, primarily as an emulsifier, and in health supplements.
Allergens
Much of the soy protein is removed from lecithin during processing but the small amount of protein remaining has been found to be responsible for allergies. Although the exact protein content is hard to measure, food-grade lecithin must be limited to 0.3 percent or 300 mg per 100 g of protein for the U.S. Food and Drug Administration to classify it as Generally Regarded as Safe, or GRAS. Despite these regulations, allergic reactions to lecithin products sometimes occur.
Symptoms
An allergic response to soy lecithin causes an over-sensitized immune system to react by producing excessive amounts of antibodies. Signs of soy allergy may be mild, such as hives or itching in the mouth. Other symptoms may include coughing or sneezing, runny hose, diarrhea, shortness of breath, swelling of the face or tongue, difficulty swallowing, drop in blood pressure, excessive perspiration or fainting, according to the Cleveland Clinic. In rare cases, anaphylactic shock or even death may result. It is common to experience a milder delayed allergic response to soy lecithin. Reactions may occur from two hours to days after exposure to soy lecithin allergens.
Trypsin Inhibitors
One of the soy allergen proteins responsible for soy allergies is called the Kunitz trypsin inhibitor, or SKTI, which has been identified in soy lecithin. SKTI is not completely metabolized in the acidic gastric environment, and survives digestion. Food processors have been unable to completely deactivate these proteins without damage to the nutrition of the soy. Although deaths from an allergic reaction to trypsin inhibitor have been documented, these incidents are extremely rare, according to "Nexus" magazine.
Considerations
If you have a sensitivity to soy, read labels carefully, as soy lecithin is contained in a variety of foods, including fast foods, chocolate, margarine and breakfast cereals.The Federal Food and Drug Act states soy lecithin must be declared on labels as an ingredient with the food source, such as soy, soya or soybeans. However, beware of many sources that are not labeled, including fast foods, baked goods and delicatessen and meat products.
References
- U.S. Food and Drug Administration; Guidance for Industry: Guidance on the Labeling of Certain Uses of Lecithin Derived from Soy Under Section 403(w) of the Federal Food, Drug, and Cosmetic Act; April 2006
- "Nexus" magazine; Hidden Dangers of Soy Allergens; Kaayla T. Daniel, Ph.D.; Aug./Sept. 2004
- Soy Connection.com: Soy Lecithin Fact Sheet
- Cleveland Clinic: Diseases & Conditions; Spy Allergy
- University of Nebraska-Lincoln; Stability of the Allergenic Soybean Kunitz Trypsin Inhibitor; Robin Roychaudhuri, et al.; 2004
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