Spices like oregano, ginger and many others disrupt the biofilm in the gut. Too much disruption would be deleterious for most people, but spices are mild in their disruptive effect, which is generally beneficial and preferable for most people to never eating any biofilm disruptors. Spices keep the biofilm to manageable levels.
I have to be careful with ginger and oregano: if I haven't taken any in many days, then I take more than a quarter teaspoon of dried oregano leaves, then too many microbes in my biofilm die, which makes me feel bad (because the dying microbes release toxins).
Point is, maybe you just need to introduce spices gradually.