A guide to soy allergy and intolerance.
[Updated May 28, 2015]
Elizabeth Arbogast's third child, Julia, was a fussy baby. She had colic and was often crying. Nothing would soothe her. Julia's apparent discomfort usually occurred shortly after each breast-feeding, which prompted Arbogast to pay more attention to what she had eaten before the infant nursed.
"Whenever I had coffee with soy milk in it or ate Tofutti Cuties (soy-based ice cream sandwiches), Julia was really cranky and seemed to be in pain," Arbogast recalls.
In addition, Julia's bowel movements weren't normal; they were runny and full of mucous. At Julia's two-month check up, Arbogast mentioned her baby's symptoms to the pediatrician. Test results, combined with Arbogast's suspicions about soy, led the pediatrician to advise Arbogast to eliminate soy from her diet.
"Within two weeks, Julia's symptoms had resolved," Arbogast says. "She was a very happy and easy baby after that.
The Problem with Soy
Food & Drug Administration (FDA) documents report that an estimated 0.2 percent of Americans are allergic to soy, although definitive studies assessing the prevalence of soy allergy are lacking. Some researchers put the estimate much higher. Eliot Herman, Ph.D., a pioneering U.S. Department of Agriculture (USDA) researcher in soybean allergenicity at the Donald Danforth Plant Science Center in St. Louis, Missouri, estimates that 5 to 8 percent of children and 1 to 2 percent of adults are allergic to soy.
Whatever the statistics, everyone seems to agree that soy allergy is a problem. According to the American Academy of Asthma, Allergy & Immunology (AAAAI), soy is one of eight foods that account for 90 percent of food allergy reactions in children. And the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA) recognizes soy as one of the eight most common food allergens, along with milk, wheat, eggs, fish, peanuts, tree nuts and crustacean shellfish.
Symptoms of a soy allergy may be limited to one area of the body or may involve many areas. They can include flushing and/or itching skin, swelling lips and/or tongue, wheezing, shortness of breath, hoarseness or tightness in the throat, nausea and vomiting, colic, abdominal cramps and diarrhea. Fatal, anaphylactic reactions to soy have been reported but are rare. Symptoms can occur within minutes to a couple hours after soy is ingested.
If symptoms are due to a true soy allergy — as opposed to an intolerance or sensitivity — diagnostic tests will reveal that the body's immune system has reacted to one of the many proteins in soybeans, produced soy-specific immunoglobulin E (IgE) antibodies, and caused a release of histamine, a substance that dilates blood vessels, thereby causing inflammation.
Simple avoidance is the primary method for treating a soy allergy, but avoidance isn’t always easy.
Soy is in many processed foods — canned tuna, baked goods, cereals, infant formulas, margarine, and many more — and is often in vitamins, supplements, over-the-counter drugs, prescription drugs, lotions and cosmetics. As Arbogast said, "It seems like soy is in everything!"
To complicate matters further, soy goes by many other names: diglyceride, edamame, glycine max, hydrolyzed vegetable protein (HVP), lecithin, miso, monoglyceride, monosodium glutamate (MSG), natto, tamari, tempeh, tofu, vegetable oil, vitamin E and yuba.
FALCPA has helped clarify the confusion somewhat. Since January 1, 2006, food manufacturers are required to clearly state on food labels if soy, or any one of the other eight most common allergens, is one of the ingredients.
However, even with the new law in place, it’s still important to read labels carefully. The law doesn’t apply to non-food items like cosmetics and medicine. And according to the FDA, FALCPA doesn’t require food manufacturers or retailers to re-label or remove products with the old labeling as long as they were labeled before January 1, 2006. As a result the FDA warns shoppers of “. . . a transition period of undetermined length during which it is likely that consumers will see packaged food on store shelves and in consumers’ homes without the revised allergen labeling.”
Arbogast has had a lot of practice reading labels. In addition to her experience with Julia, her two older children have food allergies (not to soy). And her youngest son, Reilly, has a soy allergy as well as a suspected dairy allergy.
Having an allergy to more than one food is not uncommon. According to Sheldon Spector, M.D., of the California Allergy & Asthma Medical Group in Los Angeles, someone with a soy allergy is likely to have other allergies, “especially to the legume family.” Other foods in the legume family are navy beans, kidney beans, string beans, black beans, pinto beans, chickpeas (a.k.a. garbanzo beans), lentils, carob, licorice and peanuts.
The FDA has not yet disclosed a consensus on the minimal dose of soy protein that will cause a reaction in a soy-sensitive person.
Opinions vary about whether certain products derived from soy, such as soybean oil and soy lecithin, are safe for a soy-allergic person to ingest. According to the Food Allergy & Anaphylaxis Network’s (FAAN) website, “Studies show that most soy-allergic individuals may safely eat soybean oil (not cold pressed, expeller pressed or extruded oil).” And the FDA reports that most people won’t react to soy lecithin — but some will.
So how to gauge whether or not you or your child will react? Experts say to consult with your doctor.
Allergy or Sensitivity?
Many adverse reactions to soy are not true allergies. A soy intolerance or sensitivity is characterized by a delayed reaction caused by antibodies known as immunoglobulin G (IgG, as opposed to IgE). With this type of reaction, symptoms show up anywhere from several hours to three days after eating soy. The symptoms are sometimes similar to an allergy but can also be much broader.
According to Pamela J. Compart, MD, a Maryland-based developmental pediatrician and co-author of The Kid-Friendly ADHD & Autism Cookbook, symptoms of a food sensitivity can include fatigue, food cravings, stomachaches, headaches, depression, anxiety, panic attacks, ADHD symptoms (decreased attention, hyperactivity, impulsivity), and autism symptoms (poor eye contact, social withdrawal, decreased language, obsessions, repetitive behaviors).
The notion that a food sensitivity can cause these kinds of symptoms is “quite controversial,” according to Spector. There’s very little good evidence-based data to support these associations,” he says.
Compart is aware of the lack of data. She says she was a skeptic herself until she witnessed first hand in her clinical practice how powerful food sensitivities can be.
Many children with ADHD and autism are sensitive to the proteins in wheat (gluten) and milk (casein) and benefit tremendously from a gluten-free, casein-free (GFCF) diet. Compart has found that many of these children are also sensitive to soy.
“About 60 percent of children with autism spectrum disorders are sensitive to soy,” she estimates. Along with casein and gluten, “soy is one of the top three offending foods in terms of food sensitivities.”
Since the symptoms of soy sensitivity can be delayed up to three days, it can be difficult to determine with a food diary if soy is the problem, or — more likely — part of the problem, since children who are sensitive tosoy are also often sensitive to casein and gluten.
If you suspect food sensitivities are an issue, Compart recommends a trial elimination diet (for a time period determined by you and your child’s doctor), removing casein, gluten and soy completely from the diet, including soybean oil and soy lecithin. This is necessary, she says, because “some children will have behavioral or developmental symptoms from even these small amounts of soy exposures.”
If symptoms disappear or improve, then you can add soy back in, by itself, to see if it is tolerated. If it is, soy isn’t a problem. If it isn’t, you have your answer.
Since newborns are more likely than older infants to become allergic to foods, the most successful strategy for preventing a food allergy is to delay initial exposure. That’s why soy should not be introduced into a child’s diet until after one year of age. The AAAAI recommends that infants who are not exclusively breastfed should be given hypoallergenic formulas, such as Alimentum or Nutramigen, rather than milk or soy-based formulas.
In the future, soy may be much less likely to cause an allergic reaction. Soy researcher Herman — who discovered how to use “gene silencing” to turn off the gene responsible for the expression of the P34 protein in soy, which is responsible for some 50 percent of the allergic reactions to soybeans — is leading the way to developing a low-allergen soybean.
Recently, Herman and collaborator Ted Hymowitz, PhD, of the University of Illinois, have turned their attention to identifying conventional (not genetically engineered) lines of soybeans lacking P34. Herman says he and his colleagues “are getting close to breeding soybeans that lack the vast majority of soy allergenicity.”
Don’t expect to see these low-allergen soybeans in your grocery story any time soon. As Herman says, “Removing allergens is only the first step.” There will be years of testing to ensure that low-allergen soybeans (whether genetically engineered or conventional) are safe, that they are effective in preventing the development of soy allergy, and that they mitigate the response from those people who are already sensitized to soy.
In the meantime, when a child does develop a soy allergy, strict avoidance can help him or her outgrow it. According to Spector, certain food allergies, such as shellfish and peanut, may never be outgrown but “it is very common for a child to outgrow a soy allergy.”
Elizabeth Arbogast nursed Julia until the baby was eight months old, avoiding soy the entire time. Then she switched Julia to a hypoallergenic formula. Her diligence paid off.
“At 12 months, Julia was tested for the allergy again and was no longer allergic,” Arbogast says. The decision to steer clear of soy “was very worth it.”
This article was featured in our Summer 2007 issue.