What Is All the Fuss About Boosting Our Immunity?
“… there has never been a time in which topics like Gut Health, Immune Support, Gut Cleansing and Improvement of Gut Health have been more popular.”
Accompanying the popularization of gut microbiome science in the lay media and on the web, there has never been a time in which topics like Gut Health, Immune Support, Gut Cleansing and Improvement of Gut Health have been more popular. Suddenly experts from the fields of functional and integrative medicine, nutrition, and wellness have all jumped on this new trend. Podcasts, master classes, social media posts, and advertisements for supplements, pre- and probiotics, as well as bestselling books have all driven the frenzy around these topics, while scientific evidence from well controlled human studies to support the findings obtained in mouse models have lagged way behind. As a clinician and scientist who has studied the gut, its endocrine, nervous, and immune systems as well as the brain for the better part of my career, it is remarkable to follow this explosion of information and interest.
The “advice” that lay audiences get from books and experts on social media implies that they either have to adopt anti-inflammatory measures such as anti-inflammatory diets or supplements, or that they need interventions to boost their immune system. All implying that there is a blunted, inadequate or compromised response of the immune system contributing to many of our chronic health problems.
“… maladaptive increase in the engagement of the immune system in response to diet-induced changes in the gut microbiome does play a crucial role in most of the disorders making up our chronic non-communicable disease epidemic.”
As I explain in great detail in The Gut Immune Connection, a maladaptive increase in the engagement of the immune system in response to diet-induced changes in the gut microbiome does play a crucial role in most of the disorders making up our chronic non-communicable disease epidemic. The exaggerated, inadequately restrained response of the gut-associated immune system is not only responsible for the number of autoimmune disorders (including inflammatory bowel disorders and celiac disease), allergies (asthma, food allergies) but also for the group of chronic diseases, all of which have been increasing during the past 75 years.
Even though there are different immune mechanisms underlying these different groups of disorders, they all share one mechanism, which is the compromised ability of the immune system to turn on the brakes, once activated. An important factor in this compromised braking mechanism is related to an inadequate production of short chain fatty acids from complex carbohydrates by the gut microbiota, and the resulting insufficient activation of a group of immune cells that produce the powerful anti-inflammatory molecule interleukin 10 (IL-10). This insufficient production of the immune system’s own powerful anti-inflammatory molecules can occur long before we are born, or can develop later in life.
“… when pregnant women eat a largely plant-based diet rich in fiber, short chain fatty acid-producing microbes thrive, … which not only have an anti-inflammatory effect on the mother’s gut and body, but …. On the developing fetus as well.”
Let’s start with what happens during pregnancy. An important component of the maternal influence on the infant’s microbiome and immune system are short chain fatty acids, derived from the fermentation of dietary fiber by intestinal microbes in the mother’s gut. The amounts and types of these molecules that are produced there and transferred to her baby via the placenta depend on the maternal microbial ecosystem, which in turn is shaped by the mother’s diet. As discussed in detail in The Gut Immune Connection, when pregnant women eat a largely plant-based diet rich in fiber, short chain fatty acid-producing microbes thrive, and increased amounts of them, in particular butyrate, not only have an anti-inflammatory effect on the mother’s gut and body, but these same molecules are transferred to the developing fetus as well. Recent research suggests that butyrate not only can counteract inflammation, but also can influence the maturation and reactivity of the fetal immune system. Specifically, they stimulate the development of a population of immune cells (so called regulatory T cells), which produce anti-inflammatory molecules (in particular the cytokine IL-10) crucial for the prevention of inappropriate immune activation in the gut, leading to autoimmune diseases and allergic reactions.
Butyrate produced by the mother’s microbiota doesn’t only play a crucial role for the health of the developing fetus. In the adult, diet-induced short chain fatty acid production exerts an anti-inflammatory effect in the context of a leaky gut, reducing both the inappropriate immune activation in the gut, but also preventing the spread of the inflammation to other organs, a process called metabolic endotoxemia.
“Reduced butyrate and short chain fatty acid production leading to a hyperresponsiveness of the immune system, may also play a role in the greater susceptibility and clinical course that were observed in some patients with COVID-19 infections.
Reduced butyrate and short chain fatty acid production leading to a hyperresponsiveness of the immune system, may also play a role in the greater susceptibility and graver outcomes that were observed in some patients with COVID-19 infections. Individuals with pre-existing metabolic or cardiovascular chronic diseases were more vulnerable to the infection, and hyperreactivity of the immune system (“cytokine storm”) has been associated with more severe and longer lasting symptoms. On the other hand, patients on immunosuppressive medications have NOT been found to be more susceptible to the virus.
In summary, our bodies regulate their own immune support very effectively as long as we feed our microbes a healthy diet full of fiber and polyphenols, a group of large molecules targeted at the gut microbes. Even though messages in social media and promotions of “immune boosting” supplements may tell you otherwise, there is no scientific evidence that additional “immune support” or boosting of our immune system is needed.
Dr. Emeran Mayer is a Distinguished Research Professor in the Departments of Medicine, Physiology and Psychiatry at the David Geffen School of Medicine at UCLA, the Executive Director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience and the Founding Director of the Goodman-Luskin Microbiome Center at UCLA.