What Your Gut Bacteria Say About You

Now consider pairing that grenache with something other than short ribs. The problem here is that certain red-meat-loving gut bacteria increase your heart attack risk, found a study at the Cleveland Clinic. When microbes digest compounds in meat called carnitine and lecithin, the liver uses the byproduct to make an artery-hardener that may be even more of a culprit in heart disease than cholesterol: trimethylamine N-oxide (TMAO). Note: Only if you have bacteria in your gut that are accustomed to meat—vegans don't—could you churn out TMAO. (But burger lovers, be heartened: Scientists are working on ways to identify and eventually target the villain bacteria.)

Next: More surprising health benefits of bacteria