Our gut microbiome is constantly in contact with our environment - give it access to the good things in life
Microbiome Interconnectedness throughout Environments with Major Consequences for Healthy People and a Healthy Planet (2023)
Gut microbiota through an evolutionary lens (2021)
Spending time in nature connects us biologically to our environment through our microbiome
In a nutshell
Our gut microbiome is continually in contact with our environment and the consequences can be significant
Intrusive interventions are not always positive and should be undertaken with great care
Create and encourage microbiome transfer from a natural, healthy environment
Context
I’ll describe two papers in this review [1,2]. They are worth reading for their own sake but when considered simultaneously, they provide deep, invaluable additional knowledge of the human microbiome and how it affects our health.
First, let’s address three concepts that are used interchangeably to our detriment:
Habitat – an organism’s habitat is a subset of its environment, and is defined as the specific place or type of natural environment in which an organism (microbe, plant, animal) lives. For example human gut vs skin; felled vs intact areas in a forest
Environment - the general area, surroundings, and conditions in which a living organism exists. For example, soil, water, air; city vs farmland
Ecosystem - a community where the living and nonliving components of the environment are in continuous interaction. For example gut microbiome
The first paper [1] was published in 2023 by a large multi-national team of academics. The second paper [2] was published in 2021 by a team from Harvard and UCSD, in America.
The terms microorganisms, microbiota, and microbiome have been previously defined.
Objective and results of the reviews
The paper by the multinational team [1] is a review of available literature showing how microbiomes are connected within and transferred between different habitats and environments. They also describe how such microbiome transfers can benefit human health by, for example, providing new microbiota that in turn benefit the gut ecosystem through novel functionality.
The paper from Harvard/UCSD team [2] describes how human gut microbiota have been affected by our modern lifestyle. They go on to describe the pros, cons, and risks associated with trying to “rewild” (return to a pre-industrial state) the human microbiome.
Why are the reviews interesting?
There are three quotes from the international team [1] that cause me to think differently about the human gut environment and its ecosystem.
Firstly, connectivity is much larger than I’d previously realized.
“…microbiome connectivity between different environments is vast and has a magnitude that has been little considered or understood”
The transmission of microbiomes between different environments never stops.
“It is evident that microbiome transmission between environments occurs continuously and between most environments on Earth”
The consequences of natural microbiome transfer are large.
“Considering the ubiquitous nature of microbiome transfer, we can reasonably assume that the consequences of microbiome transfer on global ecosystem functioning and the health of our planet are very large, even if we do not yet fully understand the magnitude of the process”
The Harvard/UCSD team provides a fascinating model with which to consider the three-way relationship that exists between the human environment, our gut microbiota and us as the microbiome host. Using that model, they show how trying to fix altered gut microbiota can be beneficial or neutral, but also detrimental.
I think we can replace the authors’ “rewilding” idea with “natural” or “healthy”. If we believe that someone’s gut microbiota is changed and may be associated with poor health, how do we return it to a natural or healthy state? The Harvard/UCSD scientists cause me to wonder:
What is a healthy gut microbiome in the context of different human environments?
Living in the northern hemisphere compared to living south of the equator?
Living on a mountain compared to the coast?
A city-dweller compared to a farmer?
Should the gut microbiome of a 30-year-old man be the same as a 70-year-old woman?
Is microbiota diversity as important as we’ve assumed? The authors wonder too.
Our gut microbiome is constantly in contact with the air, water and soil in our environment
If we’re going to answer those questions, and I’d argue that we should, at least before we advocate for intrusive interventions, how do we characterise a natural or healthy state?
Consider what we have barely started to address:
Identifying major gut microbial taxa other than bacteria – e.g., fungi, archea
Identifying viruses in the microbiome
Identifying metabolites beyond short chain fatty acids and secondary bile acids such as the enormous universe of carbohydrate derivatives (glycans)
How do the reviews help me to understand health and longevity?
The first paper [1] makes it clear that each of us, whether we like it or not, is continually acquiring novel additions to our gut microbiome from other humans, animals and pets, soil, air, water, fermented and other foods. These may be new microrganisms, viruses, microbial metabolites, and numerous other environmental chemicals. Those transferred elements can affect our immune status and other aspects of our health.
The second paper [2] makes it clear that there is so much more that we need to understand about our gut microbiome and its role in human health. The authors caution that in the event of potential gut microbiome damage:
“It is clear that restoration will require a scalpel, not a sledgehammer approach”
Knowing this is all to the good as far as I’m concerned. I’ll be taking as unobtrusive an approach as I can to my gut health as follows:
Avoid an unnatural environment
Hand sanitisers, antiseptic soaps and cleaners around the house
Food treated and packaged to avoid spoilage during long supply lines
Chemicals, pharmaceuticals, processed food, and manufactured probiotics
Encourage microbiome transfer from a natural environment
Exposure to nature through walking, running, biking, and gardening
Consume a range of locally sourced animal- and plant-based foods
Regularly consume my gold-standard gut microbiome tonic – fermented food
Study outline
Both papers are literature reviews
References
Sessitsch A, Wakelin S, Schloter M, Maguin E, Cernava T, Champomier-Verges MC, Charles TC, Cotter PD, Ferrocino I, Kriaa A, Lebre P, Cowan D, Lange L, Kiran S, Markiewicz L, Meisner A, Olivares M, Sarand I, Schelkle B, Selvin J, Smidt H, van Overbeek L, Berg G, Cocolin L, Sanz Y, Fernandes WL Jr, Liu SJ, Ryan M, Singh B, Kostic T. Microbiome Interconnectedness throughout Environments with Major Consequences for Healthy People and a Healthy Planet. Microbiol Mol Biol Rev. 2023 Sep 26;87(3):e0021222. doi: 10.1128/mmbr.00212-22. Epub 2023 Jun 27. PMID: 37367231; PMCID: PMC10521359.
Carmody RN, Sarkar A, Reese AT. Gut microbiota through an evolutionary lens. Science. 2021 Apr 30;372(6541):462-463. doi: 10.1126/science.abf0590. PMID: 33926939.