Mice experiment furthers understanding of gut-mood connection

DEAR DOCTOR » I switched jobs just over a year ago to an office big on birthday cakes, group lunches and sharing homemade treats. I’ve now managed to gain almost 20 pounds and have started feeling low. My mom says she heard on television that it’s because of my gut bacteria. Is that true? Should I try probiotics?

DEAR READER » These days, with the rise in research into the billions of microorganisms that live in our intestines — bacteria, fungi, viruses and others — it can seem that all of the workings of the human body eventually lead to the gut. We already know that our gut bacteria play a significant role in countless bodily processes. The ones we understand the best at this time have to do with metabolism and immune function. But as results of new research emerge, it becomes increasingly clear that the gut-body-mind connection is both complex and far-reaching. A number of these studies, which have explored whether the gut microbiome can affect how people think and feel, have made persuasive cases that there may indeed be a connection.

With that in mind, the idea that the composition of the colonies of microbiome could have an effect on mood doesn’t seem like such a stretch. And that turns out to be the takeaway from one of the newer studies, conducted by researchers from the Joslin Diabetes Center of the Harvard Medical School. In a paper published in June in the journal Molecular Psychiatry, they came to some intriguing conclusions about what happens to the gut microbiome when its host — that’s you and me — has a sudden weight gain brought on by a high-fat diet.

The researchers began with mice that became obese after eating a high-fat diet. This increase in body weight and body fat triggered a spike in depression and anxiety, which was ascertained through a series of behavioral tests. The next step was to dose the mice with antibiotics in their drinking water, which altered their gut microbiomes. The result was a return to normal behavior patterns. When gut bacteria from the stressed-out mice were transferred to the bowels of a control group of mice, they too began to exhibit increased levels of depression and anxiety. The researchers concluded that eating a high-fat diet not only can result in obesity, but it also appears to cause changes to gut bacteria that influence brain chemistry and may lead to anxiety and depression.

While this experiment further opens a door into our understanding of the gut-mood connection, it’s not meant as a prescriptive for humans. The mice improved not because they were fed probiotics, but because antibiotics wiped out a wide swath of their gut bacteria, including those associated with low mood and increased anxiety. When the researchers achieve their next stated goal, to identify the specific microbes involved, we’ll be a step closer to understanding the specifics of the moodmicrobiome connection.

In the meantime, this onset of low feelings is something you should take seriously. We also think losing the weight you gained is important, both for your physical and mental health. We hope you will consider consulting with your family doctor, who can assess the situation and advise you.