What happens when the gut microbiome is out of whack?

There are between 10 and 100 trillion bacteria in the gut

The composition of our microbiome is essential to overall health. Anything that disrupts the balance of the trillions of bacteria may be harmful—even treatments meant to fight infection, like antibiotics.

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.

The gut microbiome's role in chronic diseases

Research shows that the microbial makeup of one's gut microbiome is associated with chronic diseases ranging from asthma to schizophrenia. Understanding these associations may reveal new ways to prevent or treat chronic diseases. In the meantime, nutritional changes—such as including more dietary fiber and unsaturated fat—appear to be the "most obvious, noninvasive, and immediate" way to alter the gut's microbiota makeup and functions.

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.

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.

What is the gut virome?

The gut microbiome's community of viruses is collectively known as the virome. It has been found to affect immune system development—important to the gut-brain axis—and has been implicated in the development of inflammatory bowel disease and Type 2 diabetes. As of early 2023, less than half of the viral sequences in the gut had been identified. Further study is needed to understand the virome's influence and therapeutic potential.

Artificial sweeteners may disrupt gut health

Some research suggests that certain sweeteners can throw off the balance of beneficial bacteria in the gut and shift the composition of the microbiome. Such changes, depending on an individual's specific gut flora and levels of sweetener consumption, could potentially affect metabolism and glucose tolerance or lead to bloating and diarrhea.

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.

Western babies often are missing a key gut microbe common elsewhere

Studies show infants in Europe and North America often lack Bifidobacterium infantis, a microbe widespread in babies in Africa and South Asia that helps digest breast milk and train the immune system. Researchers link the gap to antibiotics, formula use, and sanitized spaces.

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.

Are probiotics a scam?

Probiotics are microbes meant to benefit the gut microbiome's health when consumed. This internal cityscape is packed with thousands of species of microbes whose roles and impacts have yet to be untangled. The odds are low that the probiotics have the effects they're marketed to have, and most of the gut helpers on grocery shelves have little to no evidence of impacting gut microbiome health.

Research suggests the cleanliness of the ISS may make astronauts unhealthy

The International Space Station's sterile conditions deprive astronauts of the opportunity to strengthen their immune systems through microbial exposure. To address this problem, future missions may use probiotic-based cleaners and foster diverse microbes in space habitats.

Fecal transplants can help treat infections

Fecal transplants aim to transplant healthy gut bacteria into ill patients by transferring (literally) samples of human waste from a healthy patient to a sick patient. The technique has been shown to cure otherwise deadly Clostridioides difficile (C. diff) infections and is being studied for a range of other uses.

Invasive species may harm new ecosystems via the spread of disease

Besides damaging native species through direct interactions such as competition for resources and predation, invasive species may come from environments with greater biodiversity than the new environment. This makes them more likely to carry pathogens unfamiliar to native species, increasing the risk of biodiversity loss.

Watch how coral bleaching resembles an organism's immune system attacking itself

Microorganisms called zooxanthellae are in a symbiotic relationship with coral polyps and provide them with food created through photosynthesis. When ocean temperatures or sunlight exceed an optimal range, zooxanthellae release harmful chemicals that irritate coral cells. To protect themselves, corals sacrifice their food source and expel the colorful microorganisms, becoming white.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Candida albicans is a natural body-dwelling yeast, but it can cause yeast infections

This fungus is naturally occurring on the body, but C. albicans can become a problem when the natural balance of bacteria on the body is off-kilter, allowing this yeast to spread. It can cause anything from diaper rash to a yeast infection in the throat or vagina. It’s typically treated with doctor-prescribed antifungal medications.

Learn how environmental conditions are optimized to increase bioremediation efficacy

Through biostimulation, Indigenous microbes are provided with moisture, nutrients, or oxygen to prevent their death and ensure optimal progression of their biochemical reactions. Bioaugmentation can introduce new microbial cultures to target specific compounds not natively found in the environment, while landfarming can spread or aerate contaminated soil to improve access to contaminants.

There's an official term for the sound your stomach makes before intense diarrhea

It's borborygmi. The sound is produced when gas or liquid moves through the bowel. Peristalsis, the wave-like muscle tightening process that typically pushes food through the digestive system, produces the sound as it tries to push these substances through the body.

1 in 4 people around the world don't have access to clean water

Poor water sanitation puts people at risk of acquiring this diarrheal infection. Cholera infections are on the rise due to extreme weather events and conflict. In recent years there have been cholera outbreaks in locations that hadn't seen the disease in many years, including Haiti.

More than 20 mosquito-borne and tick-borne diseases are found in the US

Children, older adults, and people with compromised immune systems are at particular risk of poorer health outcomes from these diseases. But dog owners and outdoor enthusiasts are among those at particular risk of contracting these illnesses, which include Lyme disease, Zika, and the condition Alpha-gal Syndrome.

Breaking down various tongue disorders, from infections to genetics

Taste is one of our fundamental senses, but can be impeded by a wide variety of conditions including glossitis, angioedema, and black hairy tongue. Most are characterized by their color, shape, and sometimes change in function. Causes range from vitamin or mineral deficiencies to fluid accumulation, fungal infection, or more.

When common sounds become disturbing

Misophonia causes certain sounds to feel violating, triggering a "very visceral kind of experience" filled with extremely unpleasant emotions, including annoyance, anger, and disgust. A 2017 study found that people with misophonia have elevated activity in the brain's anterior insula—a region associated with interoception, emotional processing, and behavioral responses—when exposed to trigger sounds. Ongoing research suggests trigger sound context affects the severity and manifestation of the condition.

Organisms can possess multiple unique sets of DNA in one body

Genetic chimeras can result when cells with different DNA combine, such as when two sperm cells fertilize two egg cells, creating two embryos that then merge. In mosaicism, mutations arise within an organism after conception and can spread through cell division, resulting in diseases and forming genetically distinct anatomy.

How to prevent a worst-case scenario with synbio

Author and entrepreneur Rob Reid reviews the risks of a world where more and more people have access to the technology needed to create a doomsday bug that could wipe out humanity.

Aging results from the cumulative breakdown of cellular and tissue processes

A cumulative breakdown of cellular and tissue processes combines to result in decreased organ function, disrupting the systems driving normal human physiology. This five-minute video provides a primer on the subject, complete with a discussion of risk factors, cellular changes, and potential future treatments in the fight against aging.

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

The use of fungi to detoxify land and water—a process known as mycoremediation—has been used to clean up natural resources affected by the 2025 California wildfires.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

See images of medical cases of firework injuries shared on this 'Instagram for doctors.' (Warning: Graphic content)

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

Up to a million Girl Scouts sell about 200 million cookie boxes every spring, generating $800 million, largely because refusing a child is frowned upon

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.