WHEN YOU OPEN YOUR MOUTH and say “aah,” you tell your doctor all sorts of things even though you can’t form an actual word. The tongue, one of the body’s few organs that’s visible without a scalpel, can be a key diagnostic tool, according to Michelle Loy, MD, assistant professor of clinical medicine at Weill Cornell Medicine in New York City. “We can infer a lot about a patient by examining their tongue—hydration level, coffee or tobacco use, immune health, and vitamin deficiencies,” she says. Practitioners of Traditional Chinese Medicine (TCM), a 3,000-year-old discipline incorporating ancient healing practices, also pay close attention to the tongue, noting its size, shape, color, coating, and texture. “In TCM, the tongue is considered the gateway to our bodies,” adds Loy, who’s also a…