One school of thought is that food intolerance issues are not actually our bodies inability to deal with these foods but our bodies inability to tolerate the response intestinal pathogens have to the foods that aggravate us.
Lets just take candida for example, its a well known fact that simple sugars and carbs are the preferred food source. You eat enough of them and they fuel the candida into overdrive, giving them tons of food for reproduction which in turn causes a lot of byproducts/toxins from their gorging. These byproducts are actually what causes up issues.
Since Iodine has proven effective at controlling and elimination intestinal pathogens and Iodine use often reduces or eliminates food intolerance there may be some truth to it.