Over the past few years a growing body of research has shown that the gut microbiome influences our mental health. This connection is due to a bidirectional communication between the gut and the brain (the gut-brain-axis). In 2016, a meta-analysis (a study of all the best studies) demonstrated that the use of probiotics reduced the risk of depression in non-depressed people as well as reduced the symptoms of depression in depressed individuals.
Since 2016 there have been several studies that have replicated these findings. So what is going on? How can microscopic organisms affect our mood so profoundly? It turns out that probiotics most likely mediate our mood through their anti-inflammatory effects. Depression is associated with increased inflammation in the body. The gut helps mediate this process by being a gate keeper for pro-inflammatory molecules that can pass from the gut into the blood stream. Probiotics help block these molecules from getting into the blood and triggering inflammation. The opposite holds true as well – negative alterations in the gut microbiome, or dysbiosis, has been linked to depression and anxiety.
Probiotics also influence neurotransmitters, such as serotonin, which is involved in clinical depression and the hormone modulated by the most widely used anti-depressant drugs. The probiotic, Bifidobacterium infantis has been shown to increase levels of tryptophan, the serotonin precursor. Probiotics have also been shown to influence levels of GABA, catecholamine, dopamine, and acetylcholine.
A recent study examined the effects of the probiotics, Lactobacillus helveticus and Bifidobacterium longum on mood. The study showed an improved mood in healthy participants by alleviating symptoms of anxiety and depression. It is important to note that studies such as this one indicate that the effects of probiotics are strain specific. Sound Mind utilizes the probiotic strains found to be most effective in the clinical research.