The Promising Role of the Gut-Brain Axis in Depression Treatment
A new critical pathway to alleviate acute, circumstance-related depression.
Posted May 25, 2021 | Reviewed by Ekua Hagan
Most of us do not need statistics or studies to understand that the last 15 months took a toll on mental health. A majority of Americans intrinsically felt the fears and angst generated by the threat of the disease, as well as the protocols and shutdowns that were applied to reduce the spread.
In a recent SingleCare survey taken from 1,000 U.S. respondents, 59% reported that their mental health had been affected by COVID-19 . Within a one-month period at the beginning of the pandemic, there was a 34.1% increase in prescriptions for anti- anxiety medications, an 18.6% increase in antidepressant prescriptions, and a 14.8% increase in anti- insomnia drugs.
Very few of us were emotionally unaltered by the disease.
Yet, like with any crisis comes opportunity. For researchers like me, this concentrated trend in anxiety and depression — which crosses all socioeconomic and cultural barriers — provides a way to study potential mitigations.
We continue to learn that a critical pathway to alleviate acute, circumstance-based depression could occur through the gut-brain axis .
Perhaps the most promising aspect of this focus is the potential to democratize treatment. For centuries, and still today, comprehensive mental healthcare in America has been limited to the economic elite. Diet and supplementation are accessible ways to address depression and anxiety.
The Gut-Brain Axis — and the depression link
Indeed, gut composition mays seem to pale against the real threat of the first global pandemic in a century. However, when looking at mental health as a whole, we must consider it less of an “on-off switch” and more of a gradient dial. Any movement of the needle towards an improved sense of wellbeing is the goal — with a focus on contributing factors within our control.
In the past, scientists believed that the brain controlled everything. However, numerous studies have shown that the microbiota, or the communities of bacteria and fungi that live in our gut, impact our brain and emotions. The communication between the gut microbiome and the brain is bidirectional and occurs through neural , inflammatory, and hormonal signaling pathways.
Going further, the connection between the gut microbiome and depression is demonstrated by the subsequent factors that affect, and are affected by, the gut microbiome's composition and the onset/development of depression.
Changes to the gut microbiota in major depressive disorder adversely affect many dimensions of the gut-brain axis, including: hyperactivation of the Hypothalamic-Pituitary-Adrenal (HPA) axis, disruption of neural circuits and neurotransmitter levels, excess production of proinflammatory cytokines in the immune system, and disruption of the intestinal barrier.
Encouraging the growth of beneficial microorganisms and rebalancing the gut microbiome may be a promising step toward assisting individuals in easing their depression via the gut-brain axis.
“COVID eating” is a term that earned some traction in the last year, similar to “ stress eating ,” where one indulges cravings, typically high-fat or high sugar, to combat a sense of feeling out of control. This is likely part of our “lizard brain” fight-or-flight response, which triggers a need to store fat and calories in preparation for famine and/or migration.
In our modern-day realities, this is exactly the opposite of how our diets should address chronic and acute stress and depression.
For example, depressive symptoms have been associated with a high glycemic index attributed to an excessive intake of sugars and refined carbohydrates. Conversely, healthy eating habits that limit sugar intake and refined carbohydrates are associated with a decreased risk of depression.
These findings align with several smaller and more recent trials where considerable improvements in depression levels were observed in people who followed the so-called “Mediterranean Diet,” which is associated with a small intake of red meat; a high intake of vegetables, fruits, beans, and nuts; and a medium intake of eggs, dairy, and poultry.
In my book, Total Gut Balance , we pull from the best evidence of all diets to optimize the microbiome. In a nutshell:
Getting a bit more specific, diets high in fibers, polyphenols (flavonoids and phenolic acid micronutrients found in berries, nuts, flaxseeds, vegetables, olives, coffee, and tea), and unsaturated fatty acids (avocado, nuts, olive, peanut oils, and vegetable oils) and polyunsaturated fatty acids (vegetable oils such as sunflower, sesame, soybean, and corn oils) is associated with improving and promoting the growth of beneficial gut microbial taxa.
Probiotics and depression
There is an interesting perception that exists in the current world of wellness: that we should eat our way to optimized health. On the whole, it’s good in theory; however, science and research have indicated there are beneficial nutrients and nutrient levels that we simply cannot achieve through food consumption alone.
With the sterilization and pasteurization of our modern food systems and supply chains, one particular area where we need supplementation is probiotics.
Numerous studies conducted on both humans and animals have indicated that probiotics are associated with a reduction in anxiety and depression. Furthermore, probiotics have also effectively mitigated anxiety and depressive symptoms in a manner that is comparable to that of conventional prescription medications.
Additional studies have suggested that probiotics with such bacterial strains as Bifidobacterium infantis, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longum can rebalance the microbiome and potentially treat depression due to their ability to normalize cortisol levels, regulate the HPA axis, and reduce circulating pro-inflammatory cytokines.
Once again, the old adage “you are what you eat” rings true with mental health and wellness. Now, we have the research to pinpoint specific foods and probiotic strains that can improve the sense of well-being during the pandemic — and beyond.
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Mahmoud Ghannoum, Ph.D. , is professor and director of the Center for Medical Mycology at Case Western Reserve University and a leading NIH-funded researcher and microbiome authority.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.