First off, let's be clear: one of the most common microaggressions disabled people face is other people trying to tell them what to do. Everyone has a magic cure; everyone thinks they know how to fix you. And yes, most of it's well-meaning, but often the implication is that you don't know enough about your own illness, that you don't know your own body, and that you're not trying hard enough to get better. Furthermore, being told about someone's aunt's cousin's friend who got 100% better after trying this "magic water" can be very hurtful for chronically ill people--because there is no such thing as a cure. Many chronically ill people, like myself, suffer from disorders that do not go away. Ever. All you can do is manage the symptoms the best you can with the treatments that do help. We have to deal with that fact, and having people come up to us all the time insisting that an impossible hope exists just causes us more pain. It makes it harder to accept the truth. It also makes us feel like the person suggesting a cure doesn't believe us, which is a huge problem that chronically ill people face in society.
Plus, a lot of the time, these cures are scams. Even when they're not, they likely only have a limited impact on a limited group of people, because different bodies respond differently, even to properly tested, doctor-approved medications.
Now, most people who suggest "cures" for chronic illness focus on diet. No matter how long someone has had a chronic illness, how many doctors they've seen, or how well controlled their symptoms are, people will always comment on their diet. I've had people I barely know give me advice about healthy eating upon hearing about my disability, which, again, is insulting. The two things I've heard the most are a) go gluten free and b) eat more vegetables.
But no one ever told me about corn.