Are we equal human and bugs?!
It has long been accepted, and repeated continuously with the recent
explosion of microbiome news, that bacteria outnumber our cells 10:1. I’ve read
it over and over again in many studies. I’ve even stated how we are microbe-transferring
vehicles due to this impressive fact. Yet, one recent review left me
scratching my head and again reminded me that science is based on theories.
A good scientist attempts to disprove, build-on, or question theories. If
they can’t disprove it and can repeat the positive results, it is support that
the preconceived idea is, in fact, true. We are not supposed to hold tightly to
old ideas to keep things comfortable, such as a flat earth. There’s been many
recent controversies in scientists fudging data, but that is a topic for
another time… Anyway, it was time for me to stretch my mind once again and
remind myself to keep an open mind.
This potential game-changer study I am speaking of was released in
January in Cell. It reports:
It is often
presented as common knowledge that, in the human body, bacteria outnumber human
cells by a ratio of at least 10:1. Revisiting the question, we find that the
ratio is much closer to 1:1.
reference that the original quotation for the amount of microbes in our insides
was based on one paper that was never meant to be a final estimate, yet was and
is still used by many. (Note, that at the same time, the authors used a
literature search to estimate the number of human cells.)
complicated math, which I honestly don’t pretend to understand, they state the
following in relationship to B:H (bacteria to human ratio):
we arrive at our updated estimate of B/H =
1.3, with an uncertainty of 25% and a variation of 53% over the population of
standard 70 kg males.
variation is quite a lot…
for the differences in cell number by assessing for more than nucleated cells and doing a more
thorough review of the estimates of cells in the body by mass. Interestingly,
in their study, I found confusion as well.
variances by gender, with the expected ratio of bacteria to cells to be increased
by 1/3 that of the above estimate that is intended for a 70kg (about 150 lb
male). Furthermore, it was stated that estimates can fluctuate by age and loss
of “fecal mass.” (Going “poo.”) This didn’t leave me feeling confident about
either estimate, cell number or bacteria.
Still, Nature reports that the authors of the
study reveal that the math to estimate bacteria in our insides was overstated,
basing the count on fecal estimates, which may have been overestimated. Nature
The 10:1 myth persisted from a 1972
estimate by microbiologist Thomas Luckey, which was “elegantly performed, yet
was probably never meant to be widely quoted decades later”, say the paper’s
authors. In 2014, molecular biologist Judah Rosner at the US National
Institutes of Health at Bethesda, expressed
his doubts about the 10:1 claim, noting that there were very few good
estimates for the numbers of human and microbial cells in the body.
regardless of the count of bacteria, many agree, the impact of the microbiome
on our health remains a “big deal!” The authors of the study state:
In conclusion, we do not claim that a B/H
of ∼1 rather than ∼10 should change the importance one gives
to the subject of host-microbiota interactions. We do hope that our analysis will
correct inaccurate quantitative statements and cause people to focus on more
meaningful statements to explain the motivation for studying the microbiota.
For me, this
is a wake-up call. I’m sure they are working right now on emerging technological
advances that can pick up more than bacterial traces of DNA and/or colony
counts in stool to get a detailed estimate of what lines our insides. This may
even allow us to look at other little inhabitants such as viruses, parasites,
and non-bacterial creatures living happy among our known buggy friends. So,
even if we do have more cells than bacteria, which I’m not convinced fully of yet,
do we have more cells then non-cell residents in our insides? Will this new technology
that is to come be able to measure cells more effectively as well?
Only time will
stated above, the quantity may just not matter so much as the quality of our
little trillion friends.
week, I discussed the potency of essential oils in comparison to herbs or used
as pills on my homepage. You can read it here.
Sender R, et
al. Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host
Cells in Humans. Cell. January 2016;
Abbot A. Scientists
bust myth that our bodies have more bacteria than human cells: Decades-old
assumption about microbiota revisited. Nature. January 8, 2016.
Boswell MV, et
al. Medical Journal Peer Review: Process and Bias. Health Policy Review. 2015;18; E1-E14