Psychobiotics are probiotics that beneficially intervene in mental health by altering the gut bacteria. Psychobiotics have been shown to improve depression symptoms in patients with irritable bowel syndrome.
According to some reports, some patients with irritable bowel syndrome demonstrated relief of depression symptoms after just 4 weeks of treatment with psychobiotics. A placebo-controlled, randomized trial found significantly reduced depression scores in patients with irritable bowel syndrome after receiving the probiotic Bifidobacterium longum. Mouse model results have also demonstrated that Lactobacillus normalized metabolites known to improve depression. Psychobiotic use in patients about to undergo laryngeal cancer surgery was found to decrease stress.
Although psychobiotics have demonstrated some neurologic performance enhancement, recent animal data revealed that rats that ate a healthy diet, as opposed to a poor Western diet, actually experienced impaired mental function.