As with other food intolerance issues, soy can manifest physical symptoms of intolerance with many of the same symptoms that indicate other ailments, such as pain in the gut, nausea, vomiting, diarrhea, constipation, headaches, fatigue and wheezing and other asthma symptoms. In other words, if there are symptoms manifesting in the body that cannot be directly attributed to another cause, then it is reasonable to suspect a food intolerance.
The symptoms of a food intolerance can vary from person to person and from exposure to exposure. The symptoms will most likely vary depending on the quantity of the offending food that has been consumed, and the time of onset can be within minutes or at anytime that the offending food is traveling through the gut as it is processed by digestion. After excretion it is gone, thus allowing symptoms to begin to abate. If there is continual intake of the food, symptoms will most likely continue.
Possible symptoms of any food intolerance can be the same symptoms as so many other maladies and consequently, a food intolerance and a soy intolerance specifically can go undiagnosed or misdiagnosed as something else for years and years.
When it comes to soy, it is important to note that the soy we eat is not the same soy our grandmother’s ate. Unless certified organic, the soy we consume is genetically modified. This can present a host of symptoms and dysregulation within our systems. See also: What does GMO mean?