How humans digest food

How does food move through the body?

Food passes through the digestive system via muscle movement known as peristalsis, during which a rippling contraction slowly pushes content through tubular organs, such as the esophagus and intestines. This is similar to what happens when one squeezes a tube of toothpaste, contracting the tube behind the content and forcing the tube in front of the content to expand, allowing the content to move forward.

Visualize the different parts of the digestive tract

The digestive tract, also known as the gastrointestinal tract, runs from our mouths to rear ends. Its major components include the esphoagus, stomach, intestines, colon, and more.

Human anatomy 101: the body's systems

Human life is made possible by the body's ten major systems, which maintain homeostasis by responding to incoming sensory and biochemical input. Each system must work independently and collaboratively for the body to maintain health and respond appropriately to its internal and external environments. The bones of the skeletal system, for example, give the body its shape and protect organs while also facilitating movement with the muscular system.

The pancreas releases digestive enzymes and regulates blood sugar

The pancreas weighs about the same as a deck of cards and is smaller than the average adult human hand. This lopsided glandular organ controls blood sugar levels through insulin production and helps the body digest food by creating a neutralizing tonic filled with digestive enzymes.

Which organs can you live without?

While there are some organs (such as the heart) that people simply can’t live without, there are other organs that can be removed without a huge impact. Patients who have their appendix removed, for example, experience no changes to their daily...

How do we know what prehistoric humans ate?

Without recourse to ancient menus, how can historians know what our ancient human ancestors—as far as 3 million years ago—ate on a daily basis? Researchers evaluate several factors, including the type of teeth the species had evolved, chemical analysis of the teeth, patterns of wear and tear on teeth, as well as food scraps found in the vicinity of ancient remains. Learn the approach to discovering ancient hominin diets.

How does your body turn food into energy?

Cells get energy via a process known as cellular respiration, which involves turning glucose into ATP or adenosine triphosphate. Breaking the phosphate bonds of ATP results in usable energy being released into cells, which can then use that energy to power biological processes. This 10-minute video explains how glucose turns into ATP, giving the body the energy it needs to survive.

How the five senses share information with each other

The human body depends on information from the five sensory organs—the eyes, ears, nose, tongue, and skin—to react to the world around it. Each of these organs, in its own way, relies on complex circuitry to send signals back to the central nervous system.

Ultraprocessed foods include preservatives, dyes, sweeteners, and more

Processed foods are those that have been altered from their original state, which includes numerous processes that we consider natural, such as cooking or salting. Ultraprocessed foods contain at least one item that wouldn’t be found in a kitchen, like hydrogenated oils or high-fructose corn syrup. It’s estimated that nearly 75% of all foods consumed in the US are ultraprocessed, though that doesn’t mean that all of them are unhealthy. In fact, some, such as prepackaged whole wheat bread and soy milk, are recognized for their health benefits.

Without liver bile, human poop would be a pale silver color

Stomach acid and enzymes break down food into smaller particles, expelling a semi-fluid mass called chyme into the small intestine, where bile is added. As the intestines absorb nutrients and water, the chyme solidifies and changes color.

Americans consume 8.3 billion calories of turkey on Thanksgiving

Individuals consume an average of 3,150 to 4,500 calories at the meal, which takes the average male 10 hours to burn off.

T. rex needed the same amount of calories as 80 people every day

Tyrannosaurus rex is the most extensively studied fossil creature ever known. Every year, new research is added to the towering list of papers that try to draw …

A look at the concentrations of water in the human body and various organs

When we're born, about three-quarters of our bodies are composed of water, dropping to an average of 55-60% for the average adult. The lungs are over 80% water, the kidneys and spleen about 80%, and the heart and brain are approximately three-quarters composed of water—about the same moisture as a banana.

A deep dive into how a body decomposes

Dead bodies are, understandably, scary and unsettling. Learn about the fascinating process of decomposition that takes place in every human, and how its teeming with life.

How snake biology allows them to eat prey larger than they are

Possessing flexible skulls with elastic ligaments and unfused jaw bones, snakes can open their mouths to engulf much larger prey, and adjustable airways enable them to continue breathing while their teeth grip onto their food. Through slow digestion and specialized cells that decompose bones, some snakes can survive on a single large meal for over a year.

The biology of stress in your body

Stress is a normal human response that has evolved over millions of years to handle changes or threats in our environment. This article is a helpful overview of the biological basics of this response. While it is not harmful to our physiology in the acute setting, chronic stress can lead to damaging changes in the human body over many years.

Most cells undergo programmed, controlled death

In the average adult human, apoptosis occurs in 50 billion to 70 billion cells daily when proteins managing a cell's life cycle send signals that the cell is damaged, causing it to break apart into smaller pieces that are consumed by white blood cells. The consumption prevents damage from spreading via cell division.

America generates more trash per person than any other country on Earth

The US produces roughly 292 million tons of municipal solid waste per year, about 4.9 pounds per person per day. Municipal solid waste includes food scraps, packaging, electronics, yard trimmings, and more. About 50% of the waste ends up in a landfill.

Imagining if humans could perform photosynthesis and how it would change our anatomy

Since chloroplasts reflect green light, becoming photosynthetic would give our skin a green appearance. Because photosynthesis has efficiencies of only 5% to 9%, and humans burn 2,000 Calories daily compared to about 200 burned by a tree, becoming photosynthetic would also require us to adopt a less active, sun-filled lifestyle.

Chocolate can be deadly in humans, but only after consuming extraordinary quantities

Based on tests with mice, the lethal dose of chocolate is estimated to be no more than 1,000 mg/kg. This means that the lethal dose of dark chocolate for the average US adult is about 6.5 kilograms (14.33 pounds), or about 8,300 Hershey's kisses, in one sitting.

Watch a pro butcher turn half a pig into eight common meals

The variety of food derived from a pig is enormous—from the common hot dog to delicate capicola. Watch butcher John Ratliff transform this meat into the basis of some of the most well-known meals.

Researchers generally group gut bacteria into six different categories

The trillions of bacteria in the gut microbiome can be grouped into six categories: firmicutes, actinomycetota, pseudomonadota, fusobacteriota, bacteroides, and a broad miscellaneous category. The functions of each are complex but range from breaking down food and producing vitamins to fighting pathogens.

What causes high cholesterol?

Cholesterol is a complex health issue, and for a long time, the American Health Association recommended Americans not eat more than three eggs a week to avoid it. But scientific advancements on the impact of different types of cholesterol revealed eggs aren't so bad. So what is it, and how does it effect us? Dive into the digestive tract here.

Explore the complex relationship between calories and weight

What if you found out that weight loss is actually much more complex than "calories in, calories out" and that the 2,000 calorie-a-day recommendation may not actually be accurate?

How the world produces food, in drone photos

Drone photographer George Steinmetz spent a decade documenting the vast scope of humanity's agriculture using drone photography. Roughly 40% of the Earth's surface is dedicated to growing food, and experts suggest we must produce 60% more food than we do now to feed the projected population in 2050. Browse the absolutely stunning photos here.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Watch what the Ebola virus does inside our cells and organs in order to spread and survive.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

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.

Calculate how much of your tax dollars go to each federal program based on your income, filing status, and number of children

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

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.

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

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.

This site reaches millions of visitors who are tired of AI chatbots and seeking human connection. Pretend to be an AI chatbot and ask questions, provide answers, and draw for people in real time.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

Watch how deep-sea mining equipment collects and processes polymetallic nodules—metal-rich, potato-shaped rocks—from the ocean floor and creates environmentally damaging plumes of sediments.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

The Nasdaq's 'Magnificent 7' companies are responsible for roughly 40% of the Nasdaq 100 index's gains, while the remaining 93 companies account for the other 60%.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Explore fun facts from the USPS, including unique post office buildings, a stamp that traveled past Pluto, and more.

See how Budweiser's famous Clydesdales spend their days at Warm Springs Ranch, where roughly 70 to 80 of the beer brand's giant horses can be found at any given time.

Hear 50 years of iconic hip-hop samples, the genre's foundational looped tracks