The OP asked about leaky gut. Zonulin regulates the size of the cellular junctions in the gut. Inappropriately wide junctions allow larger and more passage, or “leak”. I don’t know how that relates to Dr Gundry because I am unfamiliar with his theories.

Although i don’t disagree with your recommendation to have a healthy gut, some people need to take action to obtain such a gut. I have celiac. Celiac disease causes an overproduction of Zonulin, wider junction, and the leakage of proteins, antigens, and antibodies into the blood. I have to maintain a strict gluten-free diet to keep that from occurring.