Got food cravings? What's living in your gut may be responsi
We all have those urges -- like if you ever you just feel like you need to eat a salad or you really need to eat meat. Researcher gave 30 mice that lacked gut microbes a cocktail of microorganisms from three species of wild rodents with very different natural diets.

The duo found that mice in each group chose food rich in different nutrients, showing that their microbiome changed their preferred diet. Your gut and your brain are in constant conversation, with certain kinds of molecules acting as go-betweens. These byproducts of digestion signal that you've eaten enough food or maybe that you need certain kinds of nutrients. But microbes in the gut can produce some of those same molecules, potentially hijacking that line of communication and changing the meaning of the message to benefit themselves.

Tryptophan is an essential amino acid that's common in food but is also produced by gut microbes. When it makes its way to the brain, it's transformed into serotonin, which is a signal that's important for feeling satiated after a meal, eventually that gets converted into melatonin, and then you feel sleepy.