The Truth About the Microbes Living in Your Gut

You may have heard a lot about the gut micro­bio­me, the com­mu­ni­ty of microor­gan­isms that inhab­it your diges­tive tract.

These microbes, most­ly bac­te­ria, have been linked to many aspects of your health, from your immune sys­tem and metab­o­lism, to your mood and brain function.

But how much do you real­ly know about the gut micro­bio­me? There are many myths and mis­con­cep­tions that cir­cu­late in the media and online, some of which may be mis­lead­ing or inaccurate.

In a recent review arti­cle pub­lished in Nature Micro­bi­ol­o­gy, two UK micro­bi­ol­o­gists, Alan Walk­er and Les­ley Hoyles, debunk 12 com­mon myths about the gut micro­bio­me. They also pro­vide a crit­i­cal assess­ment of the cur­rent state of knowl­edge in this field.

Here are some of the myths they address:

• The gut micro­bio­me is not a new dis­cov­ery. Sci­en­tists have been study­ing the microbes in the human intes­tine since the late 19th cen­tu­ry, when they first iso­lat­ed bac­te­r­i­al sam­ples from fecal matter.
• The gut-brain axis, the com­mu­ni­ca­tion between the gut and the brain, is not a recent con­cept either. Researchers have been explor­ing the con­nec­tion between the diges­tive sys­tem and the ner­vous sys­tem for cen­turies, but only in recent decades have they uncov­ered how it works in both directions.
• The human micro­bio­ta does not weigh 1 to 2 kilo­grams (2.2 to 4.4 pounds), as often report­ed. This fig­ure is based on an esti­mate that has no clear source. Walk­er and Hoyles cal­cu­late that the human micro­bio­ta prob­a­bly weighs less than 500 grams (1.1 pounds), based on the weight of fecal mat­ter, colonic con­tents, and micro­bial cells.
• The human body does not con­tain 10 times more micro­bial cells than human cells. This ratio is based on a rough cal­cu­la­tion from the 1970s that has been chal­lenged by more recent stud­ies. The actu­al ratio is like­ly clos­er to 1:1, depend­ing on fac­tors such as body mass, age, and diet.
• Babies do not inher­it their micro­bio­ta from their moth­ers at birth. While some microbes are trans­ferred from the moth­er to the baby dur­ing deliv­ery, most of them do not per­sist in the long term. The baby’s micro­bio­ta devel­ops over time and is influ­enced by many envi­ron­men­tal factors.
• The gut micro­bio­me is not sta­t­ic or fixed. It changes through­out life in response to var­i­ous inter­nal and exter­nal stim­uli, such as diet, med­ica­tion, stress, infec­tion, and aging. The gut micro­bio­me is also high­ly vari­able among indi­vid­u­als, even among iden­ti­cal twins.

These are just some of the myths that Walk­er and Hoyles address in their arti­cle. They also dis­cuss oth­er top­ics, such as the role of pro­bi­otics and pre­bi­otics, the effects of antibi­otics and fecal trans­plants, and the chal­lenges of study­ing the gut micro­bio­me in humans.

The authors hope that their arti­cle will help to clar­i­fy some of the com­mon mis­un­der­stand­ings about the gut micro­bio­me and pro­vide a bal­anced per­spec­tive on its impor­tance for human health.

They also acknowl­edge that there is still much to learn about this com­plex and dynam­ic ecosys­tem, and that more rig­or­ous and repro­ducible research is need­ed to advance this field.

The gut micro­bio­me is a fas­ci­nat­ing top­ic that has many impli­ca­tions for our well-being. But it is also a top­ic that requires care­ful inter­pre­ta­tion and crit­i­cal thinking.

As Walk­er and Hoyles con­clude: “We should be excit­ed by what we know about our gut microbes but also mind­ful of what we do not know.”