One of the most important recent medical breakthroughs has been the impact of gut flora（肠道菌群）on overall health．This dynamic mix of bacteria in the digestive tract（消化道）may affecteverything from obesity to asthma（哮喘）．

The Gut-Mood Link

Anyone who's ever experienced"butterflies"in his or her stomach knows that the gut and thebrain are connected．But until recently，scientists hadn't realized that the trillions of bacteria in ourdigestive tract may be driving the relationship．

One recent experiment suggests that you can control calm．Canadian researchers gave healthymice a mixture of antibiotics，which change the makeup of GI-tract（胃肠道）bacteria．Over twoweeks，some animals became more anxious and some less，depending on which drugs they received．

In another study，when gut bacteria from calm mice were transferred to anxious mice，the jittery（紧张的）creatures seemed less nervous．

UCLA professor Kirsten Tillisch，doctor of medicine，recently had healthy women eat a yogurtrich in certain types of"good"probiotic（益生菌的）bacteria．Two'Control groups ate yogurt withoutsuch bacteria or ate nothing．Brain scans of the probiotic-yogurt eaters indicated changes in regionsthat could be associated with a less-anxious response in fearful or stressful situations compared withthe control groups．

Scientists are even exploring whether gut microbes（微生物）might treat some brain disorders．

A new study in Cell found that mice with features of autism（自ICJ症）given a type of bacteria inhealthy human GI tracts exhibited less autism-like behavior．In a recent case report，a Bostonps} chiatrist says a course of certain probiotics and antibiotics helped relieve a patient's compulsivedisorder．

-We tend to focus on how your mood affects your body from the top down，not the bottom up，"says Dr．Tillisch．"Now we know that the gut affects how your brain responds to the environment-it's a remarkable change in thinking．"