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Bad Bacteria: Is Your Gut to Blame for Your Mental Health Condition?

Bad Bacteria: Is Your Gut to Blame for Your Mental Health Condition?

Woman in gray sweater showing red stomach pain, illustrating connection between bad bacteria and possible depressionMight the addition of a probiotic to your diet help ease day-to-day stress and anxiety? Could it also help improve depressive symptoms or other mental health conditions? The idea is actually not so far-fetched as it might sound.

Over the past few years, multiple studies have suggested that having a diverse microbiome, or thriving community of bacteria and other microorganisms in your gut, is crucial to optimal health—both in the body and the brain. The so-called “gutbrain connection” influences far more than just diet and bathroom issues. In fact, scientists are discovering that our guts and brains are intricately linked, passing information back and forth almost constantly. That means that imbalances in the gut can lead to imbalances in the brain as well—influencing our mood, cognition, and our overall mental health.

John Cryan , a neuroscientist at the Microbiome Institute at University College Cork in Ireland, has demonstrated that a diverse microbiome is critical to brain health. His lab was one of the first to show that when animals and humans are stressed out, you’ll see decreased diversity in gut bacteria.

Other studies have shown that animals who were bred with no gut bacteria have a much greater stress response than normal animals. And clinicians have long known that many individuals suffering from mental health conditions often also have a variety of gastro-intestinal problems, too.

A strong link exists. But how might you correct such an imbalance in the gut? Cryan has been looking at what happens when you add certain bacterial strains, like Lactobacillus acidophilus or Bifidobacterium longum—so-called probiotics— to the diet. Evidence in animal research suggests they might help mitigate stress levels.

“We’ve found that some of these different bacterial strains have quite strong effects on both reducing stress and improving cognition, in particular a strain Bifidobacterium longum NCIMB 41676, in healthy mice,” he says. “And it gave us the idea that it might show similar beneficial effects in humans.”

In fact, the results were so striking Cryan and colleagues decided to test the Bifidobacterium on a group of healthy individuals to see how it might affect them. The researchers recruited 22 healthy males to participate in a small clinical trial. Each were initially assessed for acute stress. Immediately following, half the group tipped a sachet of Bifidobacterium into their milk each morning for four weeks while the other half received a placebo. The participants were then assessed for stress again.

The researchers found that the individuals taking the Bifidobacterium showed a significant reduction in cortisol in response to acute stress as well as lowered self-reports of daily stress during the duration of the experiment. Cryan says the effects are small but are very “encouraging.” And while this particular trial was conducted on healthy individuals, it’s possible that probiotic use could one day be extended to help individuals who struggle with depression or other mental health conditions to stay more balanced.

Lorenza Colzato is a cognitive psychology at the University of Leiden in the Netherlands who has also demonstrated the positive effects of probiotics in a small clinical trial. She agrees with Cryan—but cautions this line of research is still in its infancy.

“We still need to see a lot more clinical trials carried out,” she says. “But the results are very promising and I look forward to them being replicated in a larger sample size.” That said, she does admit she’s added a daily probiotic, along with a magnesium and multi-vitamin supplement, to her daily regimen—it could be worth asking your doctor about adding one to yours.

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