HThe human body is mysterious. It’s full of wonders (brains, kidneys) and horrors (earwax). We spend our entire lives in these bags of flesh, and yet we don’t really know how they work, or how jeans will fit them overnight.
And the gut microbiome might just be one of the most puzzling aspects.
Gut health has become a buzzword in the wellness space. This is partly due to legitimate advances in microbiome research, which has boomed over the past two decades thanks to advances in DNA sequencing methods. It’s also partly due to social media hype and new products promising quick fixes to the nagging problem of the human condition.
Among these products are at-home microbiome testing kits, which customers can order and use to collect a stool sample and mail it in for analysis. The company then sends the customer a gut health report and dietary recommendations. According to a video posted to Instagram, Paris Hilton learned that when she sent her stool sample to Viome, a company that makes at-home testing kits and in which Hilton has invested, she learned that her “superfoods” included avocados and apples, but that she should avoid broccoli.
Thousands of posts on TikTok and Instagram claim that these kits can help treat issues as diverse as bloating, joint pain, anxiety, and “leaky gut” — a nebulous term that encompasses conditions like bloating, diarrhea, and low energy. According to the Mayo Clinic, it’s a “hypothetical condition that is not currently recognized as a medical diagnosis.”
Experts agree that the microbiome is important for human health. But many doubt the usefulness of these kits, at least for now.
We asked experts what the gut microbiome is, how it affects our health, and whether home testing kits are actually helpful.
What is a microbiome?
The microbiome is a general term used to refer to a community of microorganisms — organisms you can’t see without a microscope, like bacteria, fungi and viruses — says Dr. Jonathan Eisen, a professor and microbiologist at the University of California, Davis.
We have microbiomes on our skin, in our mouths, and in our reproductive systems. There are also ocean microbiomes, soil microbiomes, and air microbiomes.
What is the gut microbiome?
The term “gut” refers to the human digestive tract, which is the organs that make up our digestive system. These include the stomach, large intestine, and small intestine. These organs are filled with trillions of microorganisms that make up the gut microbiome. (Whether the gut microbiome itself is an organ is a matter of debate.)
What is a healthy gut and how does the microbiome affect gut health?
There is no single definition of a healthy gut, says Kira L Newman, MD, clinical assistant professor of gastroenterology and hepatology at the University of Michigan.
Every person’s microbiome is different. And unlike our genes, which are largely fixed throughout our lives, our microbiome is constantly evolving, changing based on factors like age, nutrition, lifestyle, and hormonal shifts. “It’s incredibly complicated and unstable,” Eisen says.
In general, Newman describes a healthy gut as “one that allows for the digestion of food, absorption of nutrients, and elimination of waste.”
The microbiome also helps protect our bodies from bad bacteria, says Dr Nicholas Ilot, a senior research fellow and bioinformatician at the Oxford Centre for Microbiome Studies. It does this in a number of ways. “By taking up space in the gut, it acts as a blanket, creating a barrier between our gut tissue and any opportunistic invaders,” he explains. Microorganisms in the microbiome can also compete for nutrients that some harmful bacteria need to survive. And some of these bacteria produce molecules that can help our immune system.
How does the gut microbiome affect overall health?
“It’s clear that the gut microbial community has a significant impact on mammalian health,” Eisen says.
But how the gut’s microbial balance affects specific health conditions remains largely unknown. Wellness influencers and companies that sell at-home testing kits say that knowing your microbiome balance and making dietary adjustments accordingly can boost a person’s energy, improve their skin, and help manage anxiety.
But most of these claims are based on studies that identified correlations rather than causation, Eisen says, adding that many such studies have “probably not been done in large enough populations to be convincing.”
Imbalances in the gut microbiome have in fact been linked to a range of chronic diseases, including gastrointestinal, inflammatory and metabolic conditions as well as neurological, cardiovascular and respiratory diseases, says Vijaya Surampudi, MD, a nutrition specialist at UCLA Health.
What is a gut microbiota test? Do I need one?
At-home microbiome testing kits range from $120 to $400. In addition to a gut health report that details the types of bacteria and yeast present in your microbiome at the time you collected your stool sample, many companies also provide personalized dietary recommendations based on your results. Some also offer personalized probiotics to help correct suspected microbiome imbalances.
It’s hard to talk generally about gut microbiota testing because the process isn’t standardized. “Every company uses a different methodology,” Surampudi says. And these tests haven’t been scientifically validated for their usefulness in assessing gut health, she adds.
Typically, Surampudi explains, the tests use DNA or RNA sequencing to assess the microorganisms present in a stool sample.
This process can take several weeks. By this point, the balance of the microbiome may have shifted slightly. As Ilot points out, a microbiome test provides a snapshot of your gut at a specific point in time, reflecting the food you ate in the previous days. “Will your gut be the same tomorrow? Or in a week, in a month?” he says. “It will be similar, but not exactly the same.”
Is leaky gut real?
On platforms like TikTok and Instagram, leaky gut syndrome is being touted as a potential cause of gastrointestinal distress, mental confusion, and fatigue. According to the Mayo Clinic, the theory behind this hypothetical condition is that leaky gut is both a cause and a symptom of gastrointestinal disease. If too many bacteria and nutrients from our gut leak through the walls of the intestine, toxins could enter the bloodstream and cause inflammation.
“The leaky gut hypothesis, which is how gut bacteria affect metabolic conditions and liver disease, is an active area of research,” Ilot says, and there is still a lot we don’t know.
Intestinal permeability can vary based on health and disease, Newman explains, but there is no technical definition of leaky gut. Plus, the gut is always supposed to be somewhat “leaky,” she explains, because the intestines naturally absorb water and nutrients.
So, are home microbiome testing kits effective or a scam?
Currently, microbiome testing is a useful diagnostic tool for a “limited number of diseases,” Eisen says. These include Crohn’s disease and type II diabetes.
But Newman says that “there is currently no clinical use for direct-to-consumer microbiome testing,” adding that such tests are not reliable or regulated in the same way as FDA-approved lab tests.
With these at-home tests, the results are often very variable, she explains. “A person can get two very different results from two different companies, even if they sent the same sample.”
According to Dr. Justin Sonnenburg, a professor of microbiology and immunology at Stanford University, it is relatively simple to identify the species present in the gut microbiome, but it is still difficult to draw meaningful conclusions from this data. Using these microbiome profiles to “recommend foods or predict disease is extremely difficult and is only done well by a small number of groups,” he explains.
But experts agree that while it’s difficult to draw meaningful conclusions from individuals’ microbiome profiles right now, they could be a valuable tool in the future.
“Microbiome testing could become part of our clinical trials,” Surampudi says. It could be used to assess a person’s response to a particular drug or food. “But we’re not there yet.”