This is a PhD-level question that I'm sorry to say is likely to annoy many a high school teacher or university professor trying to get their students to understand the difference between chemical and nuclear reactions. My apologies in advance, but I do think this a useful question from a physics-of-chemistry sort of view, and I'm sure I won't be the only one whose jaw will drop should the assertion prove correct.
I saw an argument years ago describing how nuclear reactions are responsible for the energy lost or gained during the formation and breaking of chemical bonds. Something about gluons or exchange particles being converted to and from energy, and this energy being the resulting reaction enthalpy.
I'll openly admit that it was years ago, and I don't remember the details — hence the question. But just as many physical reactions are actually chemical reactions — the classic example of tearing a piece of paper is actually a breaking of the covalent bonds holding the cellulose chains together — it would be intriguing if all chemical reactions were nuclear reactions.