A Dozen Myths and Misconceptions About the Microbiome

“A trillion little reasons why you can’t lose weight.” Popular media is full of clickbait headlines and soundbites like this. Astounding growth in human microbiome research has given us tantalizing insights, along with a regrettable measure of hype and misinformation, write Alan Walker and Lesley Hoyles in Nature Microbiology. So as an antidote, they point us to a dozen microbiome myths and misconceptions.

The Ratio of Firmicutes to Bacteroidetes in Obesity

If you follow the literature on the microbiome and obesity, this misconception will hit you in the face and it flows into popular media with articles like this one. With scientists telling journalists that “these gut bacteria will affect weight,” this misconception has taken root. But Walker and Hoyles tell us that it comes from rodent studies and under-powered human studies. Better methods are coming to bring more robust insights, but for now, the idea that a Firmicutes-Bacteroidetes ratio determines obesity risk is little more than speculation.

Microbiome Research Is in Its Infancy

This is an easy phrase to offer up, but it’s false. Yes, the research is growing explosively, and scientists are learning a lot. But the field is not new by a long shot. Key concepts in microbiome science date back to the 19th century.

Who Coined the Term Microbiome?

Ask Google and the answer you get is Joshua Lederberg. But that’s utterly false. The concept of the microbiome goes back to the 19th century and people were using this term more than a decade before Lederberg first wrote about it. A more accurate account is here.

10¹² Bacterial Cells per Gram of Human Faeces

This factoid is as easy to find as it is false. The real number is 10¹⁰.

Our Microbiota Weighs One to Two Kilograms

Dubious is the verdict on this common myth. Walker and Hoyles say that the true number is probably less than half a kilo.

Microbes Outnumber Human Cells Ten to One

This is a great soundbite – one of the microbiome myths with real power over our imaginations. Unfortunately, it’s false. The real number is variable and most likely in the range of a one to one ratio.

You Got Your Microbiota from Mom

Not exactly. Some microbes transfer from mother to child at birth. But every one of us winds up with a unique microbiome. Even identical twins raised in the same household. Maybe, in this regard, we are all like little snowflakes. Special.

A Pathological Microbiome Defines Most Diseases

We’ll call this one an overreach. It’s true enough that many human diseases correlate with changes in the microbiome. But no, the evidence to date is not adequate to support the claim that a “pathobiome” plays a part in most diseases.

Functional Redundancy of the Gut Microbiome

Though some of the functions that different microbes play in the gut are indeed overlapping, this claim glosses over the fact that there are critical functions that relatively few species of microbes can play. In the fast-moving science of the microbiome, nuance can get lost.

Sequencing Methods Eliminate Potential Bias

This one takes us into the methodological weeds. The idea is that by using DNA sequencing methods, scientists are eliminating the potential for biased results. These methods have been a boon for microbiome research, but they are not foolproof. Bias can enter at every step along the way.

Standardized Methodologies

The idea that adopting uniform methodologies might solve many problems seems sensible. But in reality, it could blind researchers to the limitations of the methods they adopt, say Walker and Hoyles.

Can’t Culture It All

This is one of the subtle myths of microbiome research that gets in the way of progress. Some species of the microbiome are hard to culture, and DNA sequencing technologies have reduced the reliance on culturing these microbes. But the truth is that most of them can be cultured and science can benefit from the information this effort yields.

Busting Myths of the Microbiome

This slightly tedious list serves an important purpose: to remind us to take some of the swaggering claims that emanate from the booming field of microbiome research with a grain of salt. We have a lot to learn and many myths to bust.

Click here for this fascinating article by Walker and Hoyles.

Poop Goes Neolema, photograph by Katja Schulz, licensed under CC BY 2.0

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August 2, 2023