Name something about modern mental health care that doesn't sound like quackery. Then name anything found at a "gluten-free expo" that doesn't sound like quackery.
Sure: medication therapy for schizophrenia, bipolar disorder and psychosis. All of which have controlled published studies demonstrating the indications and effectiveness of the medications used, and evidence-based recommendations for therapy. The controlled studies, published in reputable peer-reviewed literature, combined with thousands of patient-years of treatment data, lead to evidence-based medicine, which is not quackery. The gluten-free expo, well, there is evidence-based medicine on the value of gluten-free in treating celiac disease, which effects about 1% of the population.