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Food’s journey through the digestive system.
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A look at the time it takes for food to pass through the gut from mouth to anus. In a healthy adult, transit time is about 24–72 hours.
Read the article The human digestive system for further information.
Before eating: Sights, sounds and smells of food
Digestive activity begins with the sights, sounds and smells of food. Just looking at or smelling appetising food can result in the brain sending signals to the salivary glands to make the mouth water and to the stomach to secrete gastric juice.
Chewing: Ingestion 1
Chewing mechanically mixes food with saliva from the salivary glands. Amylase in saliva chemically digests starch in the food. The mixing process is lubricated by mucin , a slippery protein in saliva. Each mouthful takes approximately 30–60 seconds.
Swallowing: Ingestion 2
The food is formed into a small ball called a bolus, which is pushed to the back of the mouth by the tongue. Involuntary muscle contractions in the pharynx then push the bolus down towards the oesophagus. This swallowing reflex takes about 1–3 seconds.
Peristalsis: Ingestion 3
In the oesophagus, the bolus is moved along by rhythmic contractions of the muscles present in its walls. For a medium-sized bolus, it takes about 5–8 seconds to reach the stomach.
Time to empty: Stomach
Food is mixed with gastric juice. Strong muscular contractions in the stomach wall reduce the food to chyme – a thick milky material. The pyloric sphincter at the lower end of the stomach slowly releases chyme into the duodenum. Emptying the stomach takes 2–6 hours.
Time to empty: Small intestine
It takes 3–5 hours from entry to the duodenum to exit from the ileum. The small intestine’s structure of folds, villi and microvilli increases the absorptive surface area and allows maximum exposure to enzymes and complete absorption of the end products of digestion.
Digestion: Duodenum
Small amounts of chyme are ejected approximately every 20 seconds from the stomach into the duodenum. The chyme is mixed with secretions from the pancreas and gall bladder. These fluids contain bicarbonate, enzymes and bile salts essential to the digestion process.
Absorption: Jejunum
Peristaltic waves of muscular contraction mix and move the chyme down the duodenum and into the jejunum. It has a huge surface area created by finger-like structures called villi. These assist with the absorption of the end products of digestion into the bloodstream.
Absorption: Ileum
By the time chyme has reached the ileum, most of the digestion processes involving carbohydrate, protein and fats have occurred. Its main function is to absorb the end products of digestion and release hormones that regulate feelings of fullness.
Elapsed time: Ileocaecal valve
Undigested remains of food are passed through a one-way muscular valve into the first part of the large intestine known as the caecum – a small pouch that acts as a temporary storage site. By the time food remains have reached this point, about 5–12 hours have elapsed.
Colon time: Large intestine
The large intestine is 1.5–1.8m in length and is divided into the caecum, colon and rectum. The colon is further divided into 4 parts – ascending colon, transverse colon, descending colon and sigmoid colon. Watch this video to find out more about the function of the large intestine .
Fermentation: Colon
Slower peristaltic movements push undigested food remains along the colon, which mix freely with the resident bacterial population. The bacteria ferment some of the food remains, producing short-chain fatty acids as well other important chemicals such as vitamin K.
Mass shift: Sigmoid colon
The liquid from the small intestine changes into a semi-solid form known as a stool. The sigmoid colon temporarily stores the stool until a mass movement empties it into the rectum. Residence time in the colon ranges from 4–72 hours, with a normal average of 36 hours.
Egestion: Rectum
The rectum’s external opening, the anus, is controlled by a set of muscles. When filled by a mass movement from the sigmoid colon, the rectum is stretched and produces the desire to defecate. If inhibited, the urge to defecate subsides but returns several hours later.
Watch this animated video: Digestion of food as a follow up to this article.
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Your Digestive System and How It Works
The digestive system does important work for the body. Food isn't in a form the body can readily use, so it's the digestive system that has to break it down into parts. Through digestion, the body gets the nutrients it needs from foods and eliminates anything it doesn't need.
This is a really basic overview of the digestive system, but obviously, there's a whole lot more that goes into it that makes it all work. And, unfortunately, this also means that things can go wrong pretty easily.
Note: For the purposes of this article, we are discussing a healthy digestive tract that hasn't been altered by surgery, such as colectomy , gallbladder removal , or resection .
The Length of the Digestive System
The digestive system can vary in length from person to person but can be from about 25 to 28 feet long, with some being as long as about 30 feet in some people.
The esophagus is about 9 to 10 inches in length, the small intestine is about 23 feet long, and the large intestine is about 5 feet long, on average.
How Long It Takes for Food to Digest
The time it takes for food to digest can vary a bit from person to person, and between males and females. Studies have shown that the entire process takes about an average of 50 hours for healthy people, but can vary between 24 and 72 hours, based on a number of factors.
After chewing food and swallowing it, it passes through the stomach and small intestine over a period of 4 to 7 hours. The time passing through the large intestine is much longer, averaging about 40 hours. For men, the average time to digest food is shorter overall than it is for women.
Having a digestive condition that affects transit time (the time it takes for food to pass through the digestive system) can shorten or extend the time.
Why Digestion Is Important
We eat because we need nourishment but our food isn't something our bodies can easily assimilate into our cells. It is digestion that takes our breakfast and breaks it down. Once it's broken down into parts, it can be used by the body. This is done through a chemical process and it actually begins in the mouth with saliva.
Once the components of food are released they can be used by our body's cells to release energy, make red blood cells, build bone, and do all the other things that are needed to keep the body going. Without the digestive process, the body isn't going to be able to sustain itself.
From the Mouth to the Anus
The digestive system is one long tube that runs from your mouth to your anus. There are valves and twists and turns along the way, but eventually, the food that goes into your mouth comes out of your anus.
The hollow space inside the small and large intestines that food moves through is called the lumen . Food is actually pushed through the lumen throughout the digestive system by special muscles, and that process is called peristalsis.
When you chew food and swallow, these are the structures in your body that the food goes through during its journey down to the anus:
- Mouth: Food breakdown begins with chewing and the mixing of food with saliva. Once the food is chewed sufficiently, we voluntarily swallow it. After that, the digestive process is involuntary.
- Esophagus : Once the food is swallowed, it travels down the esophagus and through a valve called the lower esophageal sphincter to the stomach.
- Stomach: In digestion, the stomach is where the rubber meets the road. There are digestive juices that help break down the food and the muscles in the stomach mix the food up. After the stomach has done its job, there's another valve, called the pyloric valve, that allows food to move from the stomach and into the first part of the small intestine, which is called the duodenum.
- Small intestine: Once food reaches the small intestine , it's mixed with even more digestive juices from the pancreas and the liver to break it down. The peristalsis in the muscles is still at work, moving everything through. The small intestine is where most of the nutrients are extracted from food. The intestinal walls absorb vitamins and minerals. Anything that the body can't use or can't break down is moved through the entirety of the small intestine, through the ileocecal valve, and on to its next adventure in the large intestine.
- Large intestine: The large intestine doesn't do much digesting, but it is where a lot of liquid is absorbed from the waste material. Undigested materials are moved through, which can take a day or more, and then into the last part of the colon, which is the rectum. When there is stool in the rectum, it precipitates an urge to defecate, and finally, the waste materials are expelled out through the anus as a bowel movement.
A Word From Verywell
The digestive system affects so much of the rest of the body because all body systems need nourishment to function. Diseases and conditions of the digestive tract can have far-reaching implications for the rest of the body if nutrients aren't being absorbed properly. The digestive system is complex, and while there are some variations, for most people with healthy digestive systems, food takes about 50 hours to pass all the way through.
National Institute of Diabetes and Digestive and Kidney Diseases. Short Bowel Syndrome . Reviewed July 2015.
Lee YY, Erdogan A, Rao SSC. How to assess regional and whole gut transit time with wireless motility capsule . J Neurogastroenterol Motil . 2014 Apr;20(2):265-270. doi:10.5056/jnm.2014.20.2.265
National Institute of Diabetes and Digestive and Kidney Diseases. Your digestive system and how it works . Reviewed December 2017.
By Amber J. Tresca Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.
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How does food move through the GI tract?
The large, hollow organs of the GI tract contain a layer of muscle that enables their walls to move. The movement of organ walls—called peristalsis—propels food and liquid through the GI tract and mixes the contents within each organ. Peristalsis looks like an ocean wave traveling through the muscle as it contracts and relaxes.
When a person swallows, food pushes into the esophagus, the muscular tube that carries food and liquids from the mouth to the stomach. Once swallowing begins, it becomes involuntary and proceeds under the control of the esophagus and brain. The lower esophageal sphincter, a ringlike muscle at the junction of the esophagus and stomach, controls the passage of food and liquid between the esophagus and stomach. As food approaches the closed sphincter, the muscle relaxes and lets food pass through to the stomach.
The stomach stores swallowed food and liquid, mixes the food and liquid with digestive juice it produces, and slowly empties its contents, called chyme, into the small intestine. The muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material from the esophagus. The muscle of the lower part of the stomach mixes the food and liquid with digestive juice.
SMALL INTESTINE
The muscles of the small intestine mix food with digestive juices from the pancreas, liver, and intestine and push the mixture forward to help with further digestion. The walls of the small intestine absorb the digested nutrients into the bloodstream. The blood delivers the nutrients to the rest of the body.
LARGE INTESTINE
The waste products of the digestive process include undigested parts of food and older cells from the GI tract lining. Muscles push these waste products into the large intestine. The large intestine absorbs water and any remaining nutrients and changes the waste from liquid into stool. The rectum stores stool until it pushes stool out of the body during a bowel movement.
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Health Encyclopedia
The digestive system: an overview, what is digestion.
Food and drink must be changed into smaller molecules of nutrients to be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and liquid are broken down into smaller parts. The body can then use them to build and nourish cells and to make energy.
How does the digestive process work?
Digestion involves:
The mixing of food
The movement of food through the digestive tract
A chemical breakdown of large molecules of food into smaller molecules
Digestion begins in the mouth, where food and liquids are taken in. It's completed in the small intestine.
What is included in the digestive system?
The digestive system is made up of the digestive tract and other organs that aid in digestion.
The digestive tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. It consists of the following:
Small intestine
Large intestine (includes the colon and rectum)
Organs that help with digestion, but are not part of the digestive tract, are the:
Glands in the mouth that make saliva
Gallbladder
Parts of other organ systems, such as nerves and blood, also play a major role in the digestive process.
How does food move through the digestive system?
Muscles propel food and liquid along the digestive tract in a wave-like movement. This movement is called peristalsis. In general, there are 6 steps in the process of moving food and liquid through the digestive system:
The first step in the digestive process occurs in the mouth. This is where food is chewed and broken down into a size that can be safely swallowed. The start of swallowing food or liquid is voluntary. But once it begins, the process becomes involuntary and continues under the control of the nerves.
The esophagus connects the throat above with the stomach below. It's the first organ into which the swallowed food goes.
Where the esophagus and stomach join, there is a ring-like valve that closes the passage between the 2 organs. When food nears the closed ring, the surrounding muscles relax and allow the food to pass into the stomach. It then closes again.
The food then enters the stomach. The stomach completes 3 mechanical tasks. It stores, mixes, and empties:
First, the stomach stores the swallowed food and liquid. This needs the muscle of the upper part of the stomach to relax and accept large volumes of swallowed material.
Second, the lower part of the stomach mixes up the food, liquid, and digestive juices made by the stomach through muscle action.
Third, the stomach empties the contents into the small intestine.
The food is digested in the small intestine. It's dissolved by the juices from the pancreas, liver, and intestine. The contents of the intestine are mixed and pushed forward to allow further digestion.
Last, the digested nutrients are absorbed through the intestinal walls. The waste products, including undigested parts of the food (fiber) and older cells that have been shed from the lining of the intestine (mucosa), move into the colon. Waste products in the colon often remain for a day or two until the feces are expelled by a bowel movement.
Medical Reviewers:
- Jen Lehrer MD
- L Renee Watson MSN RN
- Rita Sather RN
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