CLOSE CONTACT BETWEEN MAN AND SOIL DURING OUR
EVOLUTION IS LARGELY WHAT SHAPED THE MICROBIAL
ECOSYSTEMS THAT LIVE IN AND ON THE HUMAN BODY.
However, the focus of this article is on
the beneficial aspects of getting some
dirt into one’s diet. If there’s one thing
that both the evolutionary perspective
and modern science show us, it’s that
the physical activity patterns, dietary
habits and other lifestyle conditions of
our ancient ancestors provide a good
indication of how we can achieve good
health in the 21st century. This makes
complete sense, as our genes were
primarily selected for in this ancestral
environment.6
Exposure to microbes/dirt is definitely
one of these important elements of the
Paleolithic lifestyle, and compared to
many of the other “mismatch” theories
we talk about in the ancestral health
community, the difference between
microbial exposure in a hunter-gatherer
environment and in the modern world
is especially pronounced. Even the
most “non-health-conscious” people
in today’s society eat some foods that
mimic those of our ancestors, get in the
sun once in a while and exercise now
and then—but most folks don’t even
consider the idea that getting some soil
microbes into their diet could be a good
idea. On the contrary, most people look
at dirt as a bad thing.
Man and Microbe
Humans and microorganisms have
co-evolved for millions of years, and the
abrupt disconnect between bacteria and
man —on an evolutionary timescale—
has major implications for our health.
There are good data showing that the
autoimmune conditions and inflammatory
disorders that run rampant in the modern
world are largely driven by widespread
use of broad-spectrum antibiotics,
excessive “cleanliness,” consumption
of refined diets, lack of exposure to dirt,
and other factors that have a destructive
impact on the human microbiome.4,7,8
From a genetic perspective, the human
body is 99 percent microbial, and by
significantly decreasing our contact with
nature, we’ve basically lost part of our
body, in the sense that the helminths,
bacteria and fungi that once used to be a
part of the human biome are now gone.4
The Westernized microbiome is only a
faint imprint of the microbiome of our
ancient ancestors, a loss of diversity that
leaves us open to invading pathogens
and keeps our immune system working at
half capacity. Some studies even suggest
that the disappearance of some of these
old friends could be one of the reasons
mental disorders are on the rise, as the
gut microbiome, including soil bacterium
such as Mycobacterium vaccae, can
regulate our emotional behavior.9,10
Sadly, even among youth, contact
with the natural environment is slowly
disappearing as we move more and more
toward a lifestyle characterized by video
games, indoor living and hours in front of
the computer.
Similarities Between
the Human Gut
Microbiota and
the Plant Root
Microbiota
As the attention given to the trillions
of microbes that call the human body
home has increased dramatically, so has
the attention given to soil microbiota.
We’re now starting to understand that
our connection to the soil beneath
our feet is far more important than we
realized previously. For plants, the root
is “the gut”—a place where nutrients are
absorbed and waste is excreted.
It’s interesting to note that recent
studies show many commonalities
between human gut microbiota and plant
root microbiota,11,12 a finding that supports
the idea that we should be looking to add
to our diet primarily the root microbes that
cling to organically produced plant foods.
I would go as far as to argue that we
should look at the soil bacteria that cling to
tubers and other vegetables as part of the
food, as these bugs aid in the digestion
of polysaccharides that are found in the
plant. Close contact between man and
soil during our evolution is largely what
shaped the microbial ecosystems that live
in and on the human body.
Reconnecting with
Ancient Friends
So, at this point you might be asking:
What can I do to introduce some “good”
dirt into my diet? When we think about
it, it’s crazy that we’ve gotten to a point
where something as simple as soil with
abundant organic matter can be so
hard to come by for many people. For
someone living downtown in a major city,
the natural environment of our ancient
ancestors is long gone. However, that
doesn’t mean all hope is lost. One way
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in which city dwellers can reconnect
with old microbial friends is to visit the
local farmers market, where organic,
high-quality produce is abundant. For
those who live in more rural areas,
vegetables from the backyard garden or
local farmer are great. And it’s not just
about food. Ditching the hand sanitizers,
letting kids play in the dirt, doing some
gardening and getting rid of germophobic
tendencies are all ways of returning to
a lifestyle that is more in line with our
evolutionary heritage.
For those who are
immunocompromised in some way, even
these “mild” exposures can be enough to
cause problems. However, for the vast
majority of people, ingesting some soil
that’s been clinging to quality food from
a trusted source, eating more fermented
foods and generally reconnecting with
the natural environment are all good
things. After all, microbes were around
long before we were, and as we’re now
learning, we’re actually more microbe
than man.
References:
1.
Spreadbury I. Comparison with ancestral diets
suggests dense acellular carbohydrates promote an
inflammatory microbiota, and may be the primary
dietary cause of leptin resistance and obesity.
Diabetes Metab Syndr Obes. 2012;5:175–189. doi:
10.2147/DMSO.S33473.
2.
Price WA. Nutrition and Physical Degeneration.
Price Pottenger Nutrition, 2009.
3.
Rook GA. Regulation of the immune system by
biodiversity from the natural environment: an
ecosystem service essential to health. Proc Natl
Acad Sci U S A. 2013 Nov 12;110(46):18360–
18367. doi: 10.1073/pnas.1313731110.
4.
Parker W, Ollerton J. Evolutionary biology and
anthropology suggest biome reconstitution
as a necessary approach toward dealing with
immune disorders. Evol Med Public Health. 2013
Jan;2013(1):89–103. doi: 10.1093/emph/eot008.
5.
Rook GA, Lowry CA, Raison CL. Microbial ‘Old
Friends’, immuno ɕ