As for gluten and Hashimoto's:
As circular noted, gluten consumption does contribute to leaky gut, which can then increases one's risk of an autoimmune disease, whether Hashimoto's or any other autoimmune disease (depending on one's genetics).
I follow the paleo autoimmune protocol (AIP). In that world, the stance is that no one with an autoimmune disease should eat gluten—ever. (Tomorrow, I'll see if I can find a specific citation or two to back that up. I only have a few minutes now and wanted to respond with at least something today.)
According to the National Foundation of Celiac Awareness, celiac disease and autoimmune thyroid disorders share a common genetic predisposition.
And I know that non-celiac gluten sensitivity and celiac disease also share a common genetic predisposition.
So a lot of people with Hashimoto's also have either non-celiac gluten sensitivity or celiac disease. But even if they don't, they need to heal their leaky gut to calm their immune system's overreactivity, and eating gluten hinders healing.
So when people with Hashimoto's eliminate gluten from their diet, they often experience some degree of healing and in some cases, remission. As healing occurs, thyroid antibodies decrease.
