One of my pet peeves is the media jumping on a scientific study and making far more of it than what the study’s results actually demonstrate. The one that caught my eye now was the headline: “Feeling depressed? Eat yogurt rich in lactobacillus.” I am all for research into probiotics, the bacteria in our gut that may have a variety of beneficial effects on health. Perhaps even on relieving some symptoms of depression. However, the study carried out at the University of Virginia that generated the seductive headline certainly did not demonstrate that eating yogurt can alleviate depression. So what did it actually demonstrate? That stressed mice will struggle more vigorously in a tank of water if they are supplemented with Lactobacillus reuteri, bacteria that are used to make yogurt.
The “forced swimming test” is used to determine “behavioural despair” in rodents. When a mouse is placed into a tank of water without any chance of escape it will at first vigorously swim around trying to find a way out but will within a few minutes realize its hopeless state and just sort of float, moving its legs just enough to maintain balance and keep its head above the water. The time it takes for “behavioral despair” to set in, that is when escape activity slows down, is said to be a measure of the animal’s mood. This is essentially based on the observation that treatment with antidepressants increases the time the animal struggles; in other words, it stays hopeful for a longer period.
Here is what the researchers did. They stressed mice by exposing them to noise, strobe lights, crowded housing and restraint in conical tubes. As if that weren’t enough, the cages were frequently tilted and the mice’s bedding was wetted. These were stressed animals! And when they were subjected to the forced swimming test, they quickly gave up the struggle. This is interpreted as the mice being depressed. The gut bacteria of the “depressed” mice were then analyzed and found to have fewer lactobacilli than unstressed mice. Treating the stressed mice with probiotics increased the time they actively struggled in the water, supposedly being more hopeful of escape, less “depressed.”
This study is of interest to academicians albeit I would think less so to mice. Especially so since the researchers found that reduced lactobacilli were associated with increased levels of the biochemical kynurenine, a metabolite of the amino acid L-tryptophan, that is associated with depression. So there seems to be a biochemical rational for the bacteria having an effect on the behavior of the mice.
Now, never mind that humans are not giant mice. “Behavioral despair” in trying to escape from a water tank hardly equates to depression in people. Furthermore, the mice were treated with 2 billion colony forming units (CFU) per day, which taking body weight into account would require gallons of yogurt for people since each serving usually contains 1-5 billion CFUs.
It’s depressing to see how the results of research are so often improperly conveyed to the public by the media. And that depression will not be cured with yogurt.
