Sunday, September 26, 2021
Alex Papp MD
It has become increasingly clear that there is a two-way connection between the bugs living in our gut and the activities occurring in our brain. This interconnected system is called the “gut-brain axis”. Its existence was first proposed relatively recently, in 2004, by a group of Japanese researchers, who noticed an abnormally strong stress response in mice that were raised in a sterile environment. Those mice had no gut bacteria at all.
These researchers demonstrated that adding Bifidobacterium to the gut of young mice allowed them to correct the abnormality but the same did not work for adult mice. It became clear from these experiments that bacteria in the gut (the totality of which is called the gut flora), play a role in shaping the development of the brain from the earliest stages of life. Discovering the beneficial role of Bifidobacterium, and later of another bacterium called Lactobacillus, led to the concept of probiotics, which are microorganisms with the capacity to improve certain disease conditions.
Changes in diet, stress, or taking antibiotics can alter the gut flora negatively and cause a condition called dysbiosis. Dysbiosis can cause the wall of the gut to become “leaky” which allows toxins, and even the bacteria themselves, to seep into the systemic circulation. That can lead to negative effects on the immune system, which play role in psychiatric conditions such as anxiety, depressive disorders, schizophrenia and autism.
It is even possible to cause depressive symptoms experimentally in voluntary subjects who have never been depressed before, if they are injected with the same type of bacterial toxins as the ones that are known to leak through gut walls.
Probiotics have been used as supplements to typical antidepressants or as standalone treatments for both anxiety and depression. Many studies have demonstrated comparable effects on anxiety and depression from both antidepressants and probiotics.
Growing understanding that a healthy gut flora plays a role in mental well-being has led to a growing interest in people taking them as foods, supplements or additives. Probiotics refer to products containing live, beneficial bacteria. They are one of the fastest growing segments of the health food market. A large number of websites sell “probiotics for mood” which usually contain strains of Lactobacillus acidophilus and Bifidobacterium longum.
Even though there have been numerous clinical studies with these 2, and a few other, beneficial bacteria, thus far none of them have resulted in the development of medicine-grade products, i.e. products that would be regulated by the FDA. Your best option for making a reasoned choice is to go to www.consumerlab.com, a subscription-based website specializing in the review of various vitamins and supplements. This site has the most comprehensive review of both natural sources of probiotics, such as yogurt, kefir, kombucha or other food items, and concentrates of probiotics as drinks or capsules.
The now about 2 decades’ worth of clinical research on probiotics has shown that their use does provide mental health benefits, and we encourage their judicious use. Nevertheless, at this point they still cannot be considered a reliable stand-alone treatment of depression, anxiety or similar disorders as compared to psychiatric medications.
