Mood and the microbiome

The field of psychology extends back to the earliest days of recorded history. Greek mythology named Psyche, who represented the human soul, which was affected and purified over time by human suffering and misfortunes. Over time the study of the mind and personality has undergone many metamorphoses. Modern medicine’s completion of the human genome has ushered in yet another perspective.[1]

The biology of mood

While the influence of family dynamics on the mood and personality has been known throughout time, the physiological mechanism of mood is recently discovered. Being able to inherit mood disorders such as anxiety and depression was recognized along with the discovery of other genetic diseases. This influence of the body itself over the mood is a modern revelation.[2]

Science has taught us that depression, bipolar depression, anxiety, even schizophrenia can be the result of biological processes. We now recognize that even beyond genetics, imbalances of the hormones can affect mood, such as the depression caused by hypothyroidism, or the anxiety caused by hyperthyroidism. The mood is influenced by systems as far away from the brain as the GI tract itself.

Stress and the gut bacteria

Now the newest scientific pursuit, characterizing the microbiome housed in the GI tract, has revealed an important link between the body and brain health. Researchers found that when mice were bred without any bacteria in their GI tract, they showed a disruption in the relationship between their brain and adrenal glands.

The Hypothalamic-Pituitary-Adrenal (HPA) axis regulates the stress response. It should help create healthy stress in response to a dangerous stimuli (run from the predator!) and also manage stress when the danger is actually lower than expected (don’t run; it’s not a predator. It’s just a friend knocking on the door). This second scenario, where the body should recognize that there is no real source of stress and go back to a relaxed state, is out of balance in mice without healthy gut bacteria.

Probiotics and mood

Having an altered HPA axis is related to melancholy, psychosis, major depression episodes and suicide. These are all very serious diagnoses that negatively impact the sufferer’s quality of life and productivity and which can be resistant to treatment with medications. Incredibly, in mice, dramatic improvements in these conditions were seen when strains of Bifidobacteria and Lactobacillus are introduced via administration of the probiotic.[3]

This effect has been seen in humans as well. Chronic Fatigue Syndrome typically have imbalances in their gut bacteria. In 2009, researchers were interested in whether this altered bacteria was affecting the mood of people with CFS. They divided a group of 39 CFS patients into 2 groups, half of whom received a placebo and half of whom received a probiotic containing a strain of Lactobacillus.

Just introducing one strain of Lactobacillus increased the entire GI population of Lactobacillus species and Bifidobacteria.  In addition to seeing a much healthier mix of GI flora, the anxiety of these patients improved significantly with this one simple addition of a probiotic.[4]

How do bacteria in the gut influence the brain?

How could this happen? Bacteria living in the GI tract are not merely parasitic inhabitants. Good bacteria produce vitamins, manage inflammation and metabolize substances that are present in the GI tract.

Tryptophan is an amino acid that is present in large amounts in the GI tract. It comes from food and can be used to make important substances in the body. One of the best-known products of tryptophan is serotonin. Serotonin is a brain chemical, or neurotransmitter, that strongly affects mood. Many anti-depressants target serotonin, working to keep enough available in the brain to ward off depression.

Research is starting to reveal how these good bacteria in the GI tract impact mood. When the bacteria are out of balance in the GI tract, tryptophan is not converted to serotonin. A healthy population of friendly flora will turn the large supply of tryptophan that lives in the lining of the intestines and make it into serotonin. This can have positive effects locally in the GI tract, including alleviating IBS, especially when the IBS is characterized mostly by constipation. It can also help boost levels of serotonin in the brain and blood stream.[5]

More research is needed to learn about how the microbiome affects mood, but this early research is helpful. Because many anti-depressant medications work to improve the availability of serotonin, boosting the health of the microbiome that produces serotonin may help those medications work.

If you are living with depression or anxiety, a probiotic that supports a healthy gut flora, such as Nutrivee’s Advanced Probiotic Formula may be helpful in improving your quality of life. Always discuss new supplements with your health care provider, but even if you are on anti-depressant medications, it seems that adding a high quality probiotic to your health regimen may be beneficial.



[2] Lohoff FW. Overview of the Genetics of Major Depressive Disorder. Current psychiatry reports. 2010;12(6):539-546. doi:10.1007/s11920-010-0150-6.

[3] Latalova K1, Hajda M, Prasko J.

Can gut microbes play a role in mental disorders and their treatment? Psychiatr Danub. 2017 Mar;29(1):28-30

[4] Rao AV, Bested AC, Beaulne TM, Katzman MA, et al. A randomized, double-blind, placebo-controlled pilot study of a probiotic in emotional symptoms of chronic fatigue syndrome. Gut Pathogens20091:6

DOI: 10.1186/1757-4749-1-6

[5] Nzakizwanayo J, Dedi C, Standen G, Macfarlane WM, Patel BA, Jones BV. Escherichia coli Nissle 1917 enhances bioavailability of serotonin in gut tissues through modulation of synthesis and clearance. Scientific Reports. 2015;5:17324. doi:10.1038/srep17324.

To all Nutrivee customers. Nutrivee has now been rebranded to 'Vibranelle'. PLEASE NOTE: Our Advanced Prebiotic is still the exact same formula from the same manufacturer. Our Advanced Probiotic formula has changed and is now manufactured by the same manufacturer as our Advanced Prebiotic. Please purchase through our Amazon store here

Dr Keri Layton

View Latest Articles