Dear Doctor: It seems like you can't go a day without probiotics turning out to be the cure for some ailment or another. Now we're being told they help depression. How can that be?
Dear Reader: We agree with you that probiotics are in the news quite a bit these days, and sometimes with more than a bit of hyperbole. Much of the news comes from legitimate scientific research now being done into the fascinating world of the gut biome. Having read many of the resulting papers, we can assure you that the researchers themselves are far more temperate and restrained in their findings than some headline writers, who seem to love the idea of a medical miracle.
Probiotics are live micro-organisms that are ingested for their health benefits. Found in yogurt, kefir and other fermented foods, as well as in dietary supplements, they live in our digestive tracts, particularly in the gut. There, they are believed to enhance immune function and inhibit the growth of pathogens.
The spate of recent news reports drawing a link between probiotics and depression relief are likely coming from the results of a study published last spring in the journal Gastroenterology. Researchers in Canada followed 44 adults with irritable bowel syndrome, or IBS, a bowel disorder. IBS causes abdominal pain and diarrhea or constipation, and there is evidence that probiotics can ease some of those symptoms. The subjects in this study also suffered from mild or moderate anxiety and depression, which can be common among people with IBS.
Half of the people in the study were given a certain strain of probiotic, and the other half received a placebo. At the six-week mark of the study, 64 percent of the patients taking the probiotic saw a decrease in test scores that rate depression. The placebo group's depression scores dropped half that amount, or 32 percent. Interestingly, the rate of anxiety in both groups remained the same. A final evaluation at the end of the 10-week study yielded the same results.
If you're wondering whether the depression lessened because the probiotic group felt better physically, you're not alone. But researchers also performed brain scans on the test subjects. The results of those scans led them to conclude that the probiotic reduced depression by changing brain activation patterns, specifically in the limbic system, which is the collection of structures in the brain associated with emotion and memory.
This research follows on the heels of a handful of other studies in recent years that suggest probiotics can alleviate the symptoms of depression. The thinking is this occurs because probiotics reduce gut inflammation, while simultaneously raising serotonin levels. There's even a great name for this emerging area of study -- the gut-brain axis. Communication goes both ways -- from gut to brain and from brain to gut -- via the nervous system, glands and hormones, and the immune system.
Thus far, studies into probiotics and depression have been small and brief, involving limited strains of probiotics. As researchers create larger, well-controlled and long-term studies that investigate multiple probiotic strains, the results should be fascinating.
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