Soy Allergies and Sensitivities

Soy is on the Food and Agriculture Organization’s list of the eight most prevalent food allergens. This list includes milk, eggs, fish, crustacea, wheat, peanuts, tree nuts, and soy. Together, these foods account for about 90% of food allergies.

That said, it is important to understand that these high-profile food allergies differ widely in their incidence, severity, and symptoms, and that soy protein - relative to milk and nut proteins, for example - is a relatively mild allergen. Consider the following:

• Milk and peanut allergies are each 5-6 times more prevalent than soy allergies. In fact, the true incidence of soy allergy - as confirmed by double blind, placebo-controlled food challenges - is quite low. Research indicates that allergic reactions to soy occur predominately in children less than four years of age, and most estimates agree that <1.0% of children (probably 0.2-0.4% of children) have true soy allergies. Moreover, 90% of children who have reactions to soy outgrow the allergy by age four. Given these statistics, it is safe to assume that <0.1% of adults (fewer than 1 in 1,000) are allergic to soy.
• Food allergen reaction thresholds, or the minimum oral dose of protein that elicits an allergic response, tend to be several orders of magnitude (more than 100-1000 times) higher for soy than for milk and peanut proteins. In other words, it takes 100-1000 times more soy protein than milk or peanut protein to initiate an allergic response in sensitive people.
• Soy allergies tend to produce mild symptoms relative to other food allergies. In a summary report of clinical food challenge studies, it was noted that in 80% of reported cases, symptoms of soy allergies were minimal to mild, with the remaining 20% being moderate. No severe allergic reactions to soy were reported. In comparison, milk and peanut allergies produced minimal-to-mild symptoms in 50-70% of cases, moderate symptoms in 20-30% of cases, and severe symptoms in 10-15% of cases.

In summary, soy proteins can produce allergic reactions in some people, but relative to milk, peanut, and the other high-profile food allergens, reactions to soy are less common, more difficult to trigger, and less severe.

Beyond true allergic reactions, some people may be sensitive to the “non-digestible” sugars and fiber in soy. These components can cause abdominal bloating and gas, just like the sugars and fibers in most beans and just like the lactose in milk. Such symptoms are generally reduced, if not eliminated, when people use highly refined soy protein isolates which are 90-92% soy protein and only 3-4% carbohydrate (fiber plus simple and complex sugars and starches).