What is the gut microbiome?

The gut microbiome—a complex community of up to 100 trillion microbes—has a changing composition, influenced by our life stage, diet, medications, environment, and other factors.

How the microbiome affects your health

The gut microbiome is so influential to overall human health that some researchers consider it a separate organ. Its conditions, influenced by environmental and lifestyle factors such as medication and exercise, contribute to immunity, metabolism, inflammation, medical treatment efficacy, brain development and function, and the development of disorders and diseases, including asthma, depression, inflammatory bowel disease, and Alzheimer's.

Trillions of bacteria, viruses, fungi, protists, and archaea live in our guts, producing a wide range of molecules, hormones, and more—underscoring the immune system's pivotal role in the microbiota-gut-brain axis.

What is a microbiome (and why are they important)?

Jump to: What is the microbiome? How microbiota benefit the body The role of probiotics Can diet affect one’s microbiota? Future areas of research What is the microbiome? Picture a bustling city on…

Researchers generally group gut bacteria into six different categories, with varying amounts of these microbes residing in different parts of the digestive tract.

Some animals, including certain tropical ants, have little or no microbial populations in their gut, upending the idea that all animals rely on this ecosystem to help maintain their health and proper functioning.

There are up to 100 trillion microbes in the gut, and maintaining the relative balance in this ecosystem is important for our health.

Listen to how the gut microbiome influences your emotions

The gut-microbiome connection may involve the enteric nervous system, a collection of hundreds of millions of neurons throughout the gut that transmit signals up the vagus nerve to the brain.

Gut bacteria are evolving and can acquire as many as 100 new genes per year, on average.

What happens when the gut microbiome is out of whack?

An imbalance in gut microbiome flora can lead to a condition known as dysbiosis. This condition is typically characterized by a drop in microbiota diversity and an increase in harmful unicellular and acellular organisms, such as viruses, that can negatively impact the host's immune system and overall health. Genetics, infections, dietary choices, antibiotics, food additives, artificial sweeteners, and other lifestyle and environmental factors can cause dysbiosis.

A technical review of what researchers know about the gut microbiome

This overview from the National Institutes of Health provides a deeper (but still accessible) look at the different bacteria in the gut, how the microbiome develops through life, its purpose, and more.

What's next for gut microbiome science?

A Stanford microbiologist explores what we don't yet know about the gut microbiome—such as whether we can engineer the bacterial species within it—and the current scientific advances in the field.

What constitutes a 'healthy' diet?

A natural diet, typically high in plant-based foods and low in processed foods, appears to be the main contributor to a healthy, diverse gut microbiome.

Exercise causes diet-independent changes in the gut microbiome.

Gut microbiome experiments involving transfers of gut microbes from depressed people to rodents indicate that the rodents may then display depression-like symptoms.

Can the gut microbiome drive addiction?

New research suggests an imbalance of gut microorganisms may influence the likelihood of addiction and addictive behaviors by increasing the severity of withdrawal symptoms, triggering brain inflammation in regions of impulse control, and more.

The gut microbiome's community of viruses is collectively known as the virome, but most of its viruses remain unidentified.

The reason some people love exercise may be because of their microbiome

Certain gut microbes in mice trigger dopamine release and drive motivation to exercise more. Scientists are investigating whether humans carry similar microbial patterns that influence our natural inclination towards movement, exploring how unseen microbial ecosystems may shape mammalian fitness behavior and reinforce innate reward pathways. (Some users may experience a paywall.)

Bacteria in our intestine influence the brain via the gut-brain axis.

Microbes are essential to creating the many varieties of cheese, influencing texture and taste

Microbes break down proteins and fats and produce compounds with distinct tastes. These microbes can include bacteria (like the one used to give Swiss its trademark holes), molds (like the ones that give blue cheese its distinctive veining), and countless other tiny organisms.

See how the gut and the brain communicate through a bundle of nerves running from the brain to the digestive tract, serving as both a physical and chemical link.

Farts are tiny status reports from our gut microbiome, with American adults typically passing gas more than 30 times daily.

In 2026, University of Cambridge researchers reported that a group of gut bacteria called CAG-170 may be a key marker of good health, occurring far more often in healthy individuals and less commonly in people with chronic diseases.

Gut microbiome rewrites may help reduce allergies

Researchers are investigating different strategies to determine if one day they could give people a combination of gut microbes to set them up for fewer allergies. In animal research, scientists have already prevented severe allergic responses in allergy-prone mice—supplying them with gut microbes from healthy, non-allergic human babies.

Scientists have found that the Great Barrier Reef's microbiome includes an estimated 362,802 distinct viruses and 876 distinct bacterial and archaeal species—584 of which had never been documented before 2026.

Specific gut microbiome 'fingerprints' are associated with cancer recurrence, with up to 94% accuracy.

Researchers are investigating how altering the gut microbiome may influence the development of rheumatoid arthritis, which is an autoimmune disease.

The gut microbiome may play a major role in autoimmune disease and symptom flare-ups

Certain unhealthy foods can promote gut bacterial growth and inflammation in the lining of the gut, potentially disrupting its lining—leading to a leaky gut that may allow pathogens to dribble out into the bloodstream, fueling further inflammation that can both cause disease flare-ups and set the stage for future disease development.

Visualize the different parts of the digestive tract, a roughly 30-foot tube which runs from our mouths to our rear.

Some research suggests that the gut microbiome influences our risk of heatstroke, with elevated exercise levels raising body temperature to unsafe levels and increasing gut permeability—causing a "leaky" gut.

Where do genes come from?

There are many more genes on Earth today than when microbial life first spawned on the planet about four billion years ago. Many of these newer genes grew from genetic mutations, misprints that slowly drift from the original blueprint via cellular division. If these mutations drift far enough, they can establish a new family of genes, though this process can take well over a million years.

Food passes through the digestive system via muscle movement known as peristalsis, a rippling contraction that pushes food onward through tubular organs.

Scientists seeking gut insights are attaching flatulence sensors to volunteers' underwear

This fart-tracking device detects gas generated in the gut, providing insights about gut microbial activity. The underwear sensors measure a component of what is technically called flatus—digestive system gas.

What exactly is a GMO?

A GMO, or genetically modified organism, is an organism whose DNA has been altered for specific improvement such as longer shelf life, disease resistance, or enhanced nutrition—which can benefit both farmers and consumers. While humans have used...

Metabolism, a collection of chemical reactions at the cellular level, processes food and converts it into energy to power the body.

Some dementia cases may be linked to treatable microorganism infections in the brain.

Lining up every microbe on Earth would stretch to about 105,000 light-years

There are about 10²⁷ such organisms on the planet, many of which are adapted to produce energy through uncommon reactions in unconventional environments, such as within rocks or near volcanoes on the ocean floor. Studies of these organisms have reframed astrobiologists' search for life beyond Earth by broadening the parameters under which life can exist.

Artificial sweeteners may disrupt gut health, throwing off the balance of beneficial bacteria in the gut and shifting the composition of the microbiome.

Vitamin B1 is linked to gut motility—helping fight constipation—in 2026 research

A study published in early 2026 found a link between vitamin B1 and the successful movement of food through your GI tract, known as gut motility. The work incorporated genetic and survey data about poop frequency to identify genes associated with gut motility and then separately linked poop frequency data with how much vitamin B1 people ingested, theorizing that the vitamin supports the production of acetylcholine, a neurotransmitter that stimulates GI system contractions.

How humans digest food

Every day, the average human eats close to six pounds of food—all of which must be processed by the digestive system. Ten organs collaborate to transform food that the mouth chews into the energy needed to stay alive. (Stretched out, these organs...

Western babies often lack a gut microbe common elsewhere.

A quick video on how your immune system works

Explore how your immune system's vast network of cells, tissues, and organs coordinate your body's defenses against bacteria, viruses and toxins with this 5-minute TED talk video.

A doctor answers the internet's burning questions about the gut

Gastroenterologist Dr. Ugo Iroku answers the internet's burning questions about digestion and bowel movements. Get the lowdown on what it means when your stuff is super dark, the impact of coffee on evacuating bowels, and much more.

What is a cell? A great quick overview.

YourGenome.org furnishes a collection of information on cells and how they work. Every body has trillions of cells, each serving a specific function: making proteins, processing chemicals, and creating energy. Every cell contains a genome, a set of instructions for the cell's function. Brush up on your cells for a better grasp on genetics.

Fungi can cause disease, but they’re also our planet’s key decomposers

Fungi are their own taxonomic kingdom separate from flora and fauna, acting as the key decomposers and nutrient recyclers for our planet. Watch this video to understand the diverse types of fungi and the stages of the fungal life cycle. This video illustrates how fungi species may spread, eat nematode worms, damage nearby plants, and much more.

Microplastics have been identified across human body systems, with research finding they are most commonly ingested through inhalation, drinking water, and diet before crossing barriers into organs.

The gig economy is a labor market in which workers earn money through on-demand jobs

These “gigs” are often temporary or flexible tasks, such as driving for Uber. Colloquially, the term “gig economy” usually refers to people doing jobs where they connect with people who request their services through an app.

Some organelles are believed to have once been independent cells

Mitochondria and chloroplasts, which are both responsible for energy production in cells, have DNA distinct from that of their host cells and are surrounded by cellular membranes resembling those of bacteria. Through symbiogenesis, these and other specialized structures were absorbed into larger cells, forming the modern-day biological units.

The secret lives of cells

Cutting-edge microscopy has revealed previously unseen interactions of biological molecules within their cellular environment, enabling scientists to observe and analyze the molecules in a holistic view. This podcast explains the minute advancements made over the last few decades in observing cells, revealing how scientists have come and what the future holds for the field.

How do you sequence a genome?

If the genome is made up of microscopic chromosomes, how do scientists actually sequence it? Here's a 5-minute video explaining one of the most common processes.