“Microbiome: The Inside Story”
Recently, it has become apparent that our DNA does not tell
the whole story of our individuality
and other factors, environmental factors,
play an important role in human health and disease,
thanks to two revolutions in biology.
First there was epigenetics, where diet and lifestyle changes
have been shown to turn genes on and off.
And the second, our unfolding understanding of our microbiome,
how changes in our gut flora appear to impact greatly on human biology.
Until relatively recently, the colon was viewed
as a retention tank for waste
and water absorption was its big biological function.
The problem was it was hard to get in there
and we weren’t able to grow most of the bugs in a lab.
As many as 99% of all microbes fail to grow
under standard laboratory conditions
and so how do you study something you can’t study?
Ah, but now we have fancy genetic techniques.
It took 13 years to sequence the DNA of the first bacteria ever.
These days the same feat might only take two hours.
And what we learned is that we can each be thought of as a superorganism,
a kind of human- microbe hybrid.
We have trillions of bacteria living inside us.
One commentator went as far to say, we are all bacterias,
a provocative way of acknowledging that there are more bacterial cells
and genes in our own body than there are human cells and genes,
and most of those bacteria live in our gut.
All animals and plants appear to establish symbiotic relationships
with microorganisms, and in us,
our gut flora can be considered like a forgotten organ.
Health-promoting effects of our good bacteria include
boosting our immune system, improving digestion and absorption,
they make vitamins, inhibit the growth of potential pathogens
and keep us from feeling bloated,
but should bad bacteria take roost
they can produce carcinogens, putrefy protein in our gut,
produce toxins, mess up our bowel function, and cause infections.
Researchers are still in the process of figuring out
which bacteria are which.
There are more than a thousand different types of bacteria
that take up residence in the human colon.
Just to give you a sense of the complexity,
let me show you a diagram from a typical study of gut flora.
This happens to be the largest such study done on the elderly,
showing the frailest older folks tend to harbor similar bugs,
suggesting further that it may be the lousy diet in nursing homes
that’s causing this shift, which may play a role
in ill health as we grow older as you can clearly see, in figure 4.
I mean, duh.
Thankfully, not all microbiome diagrams are that complex.
Based on studying what comes out of twins,
those that eat different habitual diets,
and stools from around the world,
it has become evident that diet has a dominant role on the bacteria
in our colon and that diet-driven changes in it occur within days to weeks.
Change our diet, change our gut flora.
The hope of impacting health through diet may be one
of the oldest concepts in medicine;
however, only in recent years has our understanding of human physiology
grown to the point where we can begin to understand
how individual dietary components affect specific illnesses
through our gut bacteria.
Milk fat on that piece of pizza, for example, may complex with bile
and feed a bacteria that produces the rotten egg gas hydrogen sulfide,
and has experimentally been associated with colitis (inflammatory bowel disease).
Fiber, on the other hand, feeds our good bacteria
and decreases inflammation in the colon.
Choline, found in eggs, seafood and poultry,
as well carnitine in red meat, can be turned into trimethylamine oxide
and contribute to heart disease and perhaps fatty liver disease,
and excess iron may muck with our good bacteria
and contribute to inflammation as well.
The good news is that specific dietary interventions
offer exciting potential for nontoxic, physiologic ways
to alter gut microbiology and metabolism to benefit
the natural course of many intestinal and systemic disorders.