[blennon]

Indeed. What's new is what sort of information is conveyed from the gut to the brain via the vagus nerve. Note: information is also conveyed in the other direction from the brain to the gut.

This study shows that your gut is equipped with environmental sensors (enteroendocrine cells) that can convey nutritional information from the gut to the brain on short time scales (~seconds or faster). It's like your gut's "eye" in that it can "see" what's going on, like sugars are present, and convey this to your brain.

I'm not an expert on the gut-brain field but I've always wondered where food cravings come from, especially specific ones that pregnant women often exhibit. E.g. craving dirt. My conclusion is that your body must have a way of sensing what nutrients you're ingesting and missing.