Each doctor in the field of functional medicine can share tales about the ‘probiotic miracle’ – instances where patients, often suffering from severe, obsessive-compulsive spectrum symptoms, saw complete remission after changing their diets and adding probiotic supplements. Is this some sort of mystic phenomenon, or is it backed by a growing comprehension of the microbiome’s influence on mental health and behavior?
For the last twenty years, groundbreaking researchers have been validating inflammatory models of mental disorders like depression, bipolar disorder, and schizophrenia. Studies have concentrated on markers indicating immune distress in a significant subset of patients, a majority of whom are classified as “treatment resistant”. Through this research, we have discovered that depression can be induced in both animals and humans by inflammatory agents. It’s also been found that depression has a linear correlation with blood levels of inflammatory markers, meaning more markers equate to worse depression. Moreover, symptoms can be alleviated using pharmaceutical anti-inflammatories.
The gut’s role in inflammatory models of mental illness
Given this information, where should we start when we’re considering natural ways to modify the body’s inflammatory states? The answer is the gut, which houses over 70% of our immune system. The gut is our intermediary between the outside and inside worlds, separated by a single layer of cells. The resident microorganisms in our gut, outnumbering our human body cells by a ratio of 10:1, form an ecosystem through exposure to the postnatal environment, including the vaginal canal, breastfeeding, and our immediate surroundings. Disruptions to this bacterial balance from medications, gluten, herbicides, stress, and infections can prime our innate immune system for attack. Depression, which is linked with compromised integrity of this intestinal barrier, becomes a maelstrom of inflammation, cellular machinery impairment (e.g. mitochondria), oxidative stress, and more inflammation in a continuous cycle. Specifically, depression is linked with increased levels of lipopolysaccharide (LPS), an inflammatory toxin produced by bacteria that are supposed to stay within the gut.
If depression is a collection of symptoms driven downstream by inflammation, oxidative stress, and mitochondrial dysfunction, what lies at the source? Data from both animals and humans suggest that disruptions to our gut ecology may be a major contributor, bringing the microbiome into the spotlight of advanced psychiatric research.
The term “psychobiotics” refers to a live organism that, when consumed in sufficient amounts, provides a health benefit for patients suffering from psychiatric illness. A review by Dinan and others provides the clinical basis for using probiotics in mental health, referencing animal studies where behavioral changes were observed after exposure to certain bacterial strains like bifidobacterium and lactobacillus. In placebo-controlled trials in humans, it was shown to reduce symptoms of anxiety, chronic fatigue, and depression and anxiety associated with irritable bowel syndrome.
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