Inside your gut is a large ecosystem of mostly harmless bacteria that live in the gastrointestinal tract.
The gut microbiome is a fascinating collection of bacteria and other microorganisms that has been connected to a wide range of health concerns, including autism spectrum disorder, diabetes, depression, Alzheimer’s disease, and movement disorders.
But, despite what researchers have uncovered about the gut microbiota, there is still a lot we don’t know – and a stack of falsehoods that appear to need to be debunked.
After scouring the literature, UK microbiologists Alan Walker from the University of Aberdeen and Lesley Hoyles from Nottingham Trent University weigh in on 12 myths and misconceptions about the gut microbiome, which are fueled in part by the gut microbiome’s enormous potential for human health.
“While truly exciting,” Walker and Hoyles write, “the increasing focus on microbiome research has unfortunately brought with it hype and entrenched certain misconceptions.”
“As a result of constant repetition, many unsupported or under-supported statements have become ‘facts.'”
While some of these beliefs are minor, others are more pervasive, and Walker and Hoyles suggest that cumulatively, they could stymie development and public trust in science.
So let’s get into some of the more juicy misconceptions on the list. Take note of the mucous.
To begin with, microbiome study is not a new field; it dates back at least to the late nineteenth century, when the first bacterial samples were isolated from the human intestine.
Similarly, the gut-brain axis, or the unexplained relationship between the body’s bowels and the mind, has been studied for generations. Only recently have we realized how that relationship works in both directions.
Now for some figures. The human microbiota is believed to weigh between 1 and 2 kilos (2.2 to 4.4 pounds). However, Walker and Hoyles were unable to locate the original source of this frequently referenced number.
Instead, they estimate that the human microbiome weighs 500 grams or less. Their updated estimate is based on the weight of a typical human feces (200 grams wet weight), the percentage of bacteria (approximately half), and the weight of colonic contents.
Similarly, certain ‘back of the envelope’ calculations in the 1970s led to the hypothesis that the human body contains ten times as many individual bacteria as its own cells.
Researchers have already attempted to dispel this myth, discovering that the ratio is most likely closer to 1:1. Obviously, if we see those figures again, it’s worth reiterating.
Another widely held belief is that kids ‘inherit’ their mothers’ microbiota at birth. While some germs are directly transferred after birth, research indicates that just a few species remain with us throughout our lives.
A mother’s microbiota may provide newborns a temporary health boost, but our microbiome is shaped by our diet, antibiotics, genetics, and the environment we live in.
“Every adult, even identical twins raised in the same household, ends up with a unique microbiota configuration,” Walker and Hoyles write.
The subsequent myths are a little more technical, including the lab activity of busy microbiologists.
But the last one is arguably the most intriguing: whether changes in a person’s gut flora lead to disease.
Researchers struggle to identify clear trends because “such alterations are rarely consistent, and the microbiota is hugely variable between individuals, both in health and disease,” Walker and Hoyles write.
Age, BMI, medication, as well as a person’s metabolism and immune system, can all influence microbiota composition, making it difficult to separate any possible cause and effect in observational research.
The perspective has been published in Nature Microbiology.