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Dr. Emeran Mayer on The Gut-Immune Connection

Our bodies have been under siege, and not just due to COVID. Dr. Emeran Mayer explains that it’s because we have disrupted our gut microbiomes.

Despite advances in medical science, Americans are getting sicker and sicker—fighting obesity, heart disease, neurodegenerative disorders, depression, allergies, and autoimmune disorders. Why? Emeran Mayer, MD has some answers.

Mayer is a distinguished research professor at the David Geffen School of Medicine at UCLA and a world-renowned gastroenterologist and neuroscientist who has spent decades studying brain-gut interactions. He’s found that many of our health problems are connected to how well our gut microbiome is doing.

In his book The Gut-Immune Connection: How Understanding Why We’re Sick Can Help Us Regain Our Health, he shares ways to become healthier so that we can fight off both non-infectious chronic health conditions as well as acute attacks from something like the coronavirus.

S&H: Food, health, and the environment, as well as racial inequalities found in those areas, have been increasingly talked about since the pandemic. Does this make your type of work easier, knowing that the public is connecting the dots? Is the public connecting the dots?

Dr. Emeran Mayer: The key philosophy underlying The Gut-Immune Connection book is the interconnectedness of food, gut health, plant and soil health, and planetary health, and makes the case for the One Health concept, that encompasses all these dimensions.

I do mention repeatedly the socioeconomic dimension, which obviously plays a major role in the current chronic disease epidemic, but did not make it a main focus. My mission in my book and in my SM outreach is to increase the public awareness about this interconnectedness, and change their short-term focus on personal health and weight loss to a sense of wider responsibility as part of the One Health concept. Unfortunately, only a small percentage of the population is currently aware of this close interconnectedness.

In the introduction to The Gut-Immune Connection, you write that there’s a growing body of scientific evidence that shows different types of largely plant-based diets are not only associated with better health, but actually play a causative role. Can you please explain that nuance from a medical standpoint?

Associations or correlations between a largely plant-based diet and different aspects of health are impressive and are often used to recommend such a diet, but they could be the cause of many lifestyle factors that are not directly related to the diet. For example, individuals who have chosen a vegan, vegetarian, or Mediterranean-type diet are likely more health-conscious, exercise more, have a higher socioeconomic status, live in healthier environments, are more mindful, etc. So the fact that better health is associated with such diets could be related to any of these factors, rather than the diet itself.

However, there is a slowly growing number of longitudinal and prospective studies which compare the health outcomes of two randomized groups, one consuming a healthy, largely plant-based diet, and one an unhealthy one.

On page 24 of The Gut-Immune Connection, you talk about the history of gut communication and the “second brain” of the gut. And then you mention it’s actually our first brain. Can you please explain that a little to us? Do you mean it’s more important or that it came first?

The name “second brain” was coined by my colleague Michael Gershon in a book he wrote more than 10 years ago. He is an expert on the enteric nervous system and has always emphasized how many similarities it has with our central nervous system (­i.e. our big brain).

However, from an evolutionary standpoint, as I point out in my book, the nerve nets surrounding the primitive digestive tubes of the first marine animals came long before any central nervous system, and their main function of regulating gut function has been preserved throughout evolution all the way to our human enteric nervous system.

Our brains have developed much later by adapting many features of this first gut-based nervous system, such as neurotransmitters and nerve types. Both our first enteric nervous system and our central nervous system are crucial, one for the day-to-day regulation of basic gut functions, the other one for regulating all our organ systems and for making us humans.

How close are researchers to understanding what should be in the microbiome? I understand there is not yet a sense of what is “normal” to even measure against?

We currently don’t know what the microbiome of an individual with optimal health and wellness should look like, except some general requirements, like diversity and richness, and a high production of anti-inflammatory short-chain fatty acids. We are beginning to understand the gut microbiome composition and function of individuals during the lifespan, including those who live into their 90s in full physical and mental capacity.

What will take longer is to identify specific gut microbial metabolites that play a role in various diseases, including cognitive decline, Parkinson’s disease, and autism spectrum disorders. I think that dramatic progress will be made in the next 10 years.

There is sometimes a tendency among gastroenterologists to dismiss dietary factors (not you, of course). Why has there been this reluctance in the field, and are you seeing it change?

The reluctance is really based on ignorance and on the almost complete lack of training of students in medical school in clinical nutrition. Also, the modern medical system focuses on revenue-generating aspects of the profession in the form of procedures, medications, supplements, and surgeries, not on counseling in healthy nutrition.

What simple change do you wish people would start with in pursuit of better health? Eating more veggies? Stop buying super-processed foods? Give us a Dr. Emeran Mayer No. 1 hit.

Change their lifestyle, starting with a healthy diet, but also incorporating mind-based strategies, regular daily exercise, and good sleep. The simplest change is to switch from the standard American diet to a largely plant-based Mediterranean type diet, eliminating any ultra-processed foods, any added sugar.

How hopeful are you that America can turn its gut-health crisis around?

I am unconditionally optimistic and see many positive developments in consumer preferences, in particular in younger people. On the other hand, the headwinds are formidable: Industrial agriculture, large food corporations, and the medical and pharmacological-industrial complex have a vested interest in keeping things the way they are. Ultimately, it will take a revolution at all levels of society to turn things around.

Read Our review of The Gut-Immune Connection appears in the May/June 2021 issue.


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