Inflammation

Soy allergies and soy sensitivities

by Dixie Mills, MD

At the clinic, we will often recommend soy as a natural, therapeutic treatment to help women with many aspects of their health, including hormonal balance, because so many of our patients find it helpful. As I discuss in my article on the soy controversy, researchers have found soy to be safe in therapeutic amounts.

Yet some people continue to talk about soy as though it were poisonous, or as though it will have detrimental effects on our children. While this is not true, a small proportion of people do have sensitivities or allergies to soy. So it is worth looking at what can happen when you’re sensitive or allergic to soy, and how you can work with this sensitivity to decide whether soy is something you want to include in your diet.

Soy sensitivity versus soy allergy: what’s the difference?

When it comes to allergies and sensitivities, every woman’s body uses and digests soy proteins, sugars, and isoflavones differently. Sensitivity to soy can create, among other things, digestive problems and inflammation. This can be a genetic issue, a function of diet, a lack of digestive enzymes or co-nutrients, or an imbalance of the beneficial bacteria that live in the digestive tract. But difficulty digesting soy, and being allergic to the food, are not the same thing. An allergy is a situation where your body considers a substance to be foreign, and marshals an immune response to it — sometimes a strong one.

Soy sugars. When you’re sensitive to soy, digestive problems occur because soy contains two sugar compounds, raffinose and stachyrose, that humans are unable to break down without some help. Soy isoflavone molecules are also attached to sugar molecules (for example, genistin is the glucoside, or sugar-containing form of the isoflavone genistein), and they, along with soy proteins, must be processed in the colon by native bacteria that produce gases such as carbon dioxide, hydrogen, and methane. Some argue that only fermented soybean products like soy sauce and miso are safe because the sugar molecules in soy get split off in the fermentation processes used to produce them.

Soy and trypsin. Others claim that only fermented soy products and tofu are digestible, because raw soybeans contain trypsin inhibitors or other “antinutrients,” which they say counteract our ability to digest and absorb proteins. But many legumes and other plants contain trypsin inhibitors and other factors that affect their digestibility, including green beans, kidney beans, and lima beans — even corn!

Soy, digestive enzymes, and gut flora. Some legumes may be completely indigestible, even when cooked. But not all. And most people are able to split the sugars off and break down various legume proteins — though not everyone. The discomfort some people experience after eating soy and other beans can depend on their digestive enzymes and the type or amount of bacteria in their gut. It can also depend on the variety of bean, and how and when it is harvested.

Soy and the thyroid. Some women with thyroid concerns may also experience a response to the isoflavones in soy, but this directly relates to thyroid function rather than an inflammatory response per se, and may be managed by moderating intake and correcting an iodine and/or selenium deficiency. See our article on goitrogenic foods for more information.

An allergy to soy is a very different matter — one that is uncommon, fortunately. But there is a great deal of confusion and misinformation about soy’s allergic potential, mainly centered around the highly emotional discussion of whether it causes serious health problems in babies who are fed soy infant formula. So let’s take a look at that issue and see if we can sort out the truth from the fiction.

Soy infant formula and allergies

Of the top eight foods that cause 90% of food allergies, soy ranks last on the list. Still, as a precaution, it is now being listed as an allergen on all products that might contain it here in the US. You may have already seen “This product may contain soy” on labels for everything from ice cream to margarine.

Several anti-soy groups have turned their focus onto soy infant formula, using people’s emotions about infant health to make it a “hot button issue” and support a larger case against soy. Among their arguments is the supposed potential for allergic response in infants, leading to colic, gastrointestinal problems, “stunted growth,” or even anaphylactic reactions. While any food has potential for causing an allergic reaction (in adults as well as in babies), the truth is that soy is among the least likely of several common foods to cause such serious responses. As you can see in the chart above, when researchers looked at the incidence and severity of soy allergies, they found people had much more severe and frequent allergic reactions to the proteins found in cow milk than to the proteins in soy. In infants, only around 10% of those who were allergic to cow milk were also allergic to soy formula.

I would also like to point out that babies have been fed soymilk for nearly a hundred years, and as of today (aside from thyroid disease and the relatively rare, true soy allergy), there simply are no data to support detrimental effects. In fact, recent studies on the use of soy-based infant formulas indicate that soy proteins do not have hormonal effects in long-term feeding, and that “isoflavones in soy infant formulas do not adversely affect human growth, development or reproduction.”

Mother Nature so wisely designed breastfeeding to benefit our infants in every way, helping them build a robust immune system and protecting them from allergies, sensitivities, and digestive problems. Even so, we’re now learning that genistin, one of the most common soy isoflavones, can help prevent and decrease severity of rotavirus infections, a common gastrointestinal illness for infants, especially in poorer countries.

So while it’s true that soy protein can be allergenic, all food proteins have this potential, so that’s not a good reason to eliminate soy as a viable substitute for cow milk. In feeding our babies, I think everyone would agree these days that breast milk is best. But when a baby cannot be breastfed, for whatever reason, soy offers a reasonable alternative.

Choosing soy... or not!

If you don’t have a soy sensitivity or allergy, then whether you include soy in your diet is simply a matter of personal preference. Soy foods such as tofu, soy milk, and edamame can be delicious sources of beneficial soy proteins (see our article on the health benefits of soy for more nutritional information). You can also use supplements in the form of bars or shakes, keeping in mind that whole bean products are best.

Obviously, if you do have a soy allergy, please do avoid soy, just as you would any other allergen! But if you are sensitive to soy, rather than truly allergic, it doesn’t mean you’re obligated to avoid it. When our patients report bloating, gas, or other intestinal discomfort after eating soy foods, we advise them to try a soy and yeast-free diet, colon cleanse, or detox. You can also try limiting your intake to organic or non-GMO soy only, or use only fermented soy products. Those with problems digesting beans will often benefit from digestive enzymes and probiotics (such as Beano or the kind we offer in our Personal Program), or by adding sea vegetables or digestive spices such as ginger or cumin to their soy dishes. Or, maybe you decide that you just don’t want to go to the trouble — and that’s okay! Your health is in your hands, and by listening to your own wisdom, you can make decisions that are right for you.

Related to this article:

References & further reading on soy allergies and soy sensitivities

 

Last Modified Date: 04/20/2011
Principal Author: Dixie Mills, MD