How Digestion Works Step by Step

Reviewed on 7/18/2022
Children looking at a science model of the human digestive tract
The order in which food progresses through the digestive system is as follows: the mouth, esophagus, lower esophageal sphincter, stomach, small intestine, large intestine (colon), and rectum.

Digestion is the process by which your body breaks down the foods you eat into the nutrients such as proteins, fats, carbohydrates, vitamins, minerals, and water that the body needs for survival. 

The digestive system breaks down these nutrients into smaller components that the body can use for energy, growth, and cell repair.

  • Proteins break down into amino acids
  • Fats break down into fatty acids and glycerol
  • Carbohydrates break down into simple sugars

Foods move through the gastrointestinal (GI) tract, which runs from the mouth through the anus. Food progresses through the digestive system as follows: 

  • Mouth
    • The first part of the digestive system
    • Foods you eat are chewed and saliva produced by the salivary glands helps moisten food and enzymes break down starches
    • The tongue helps push food into the throat
    • The epiglottis, a small flap of tissue, folds over the airway to prevent choking as the food passes into the esophagus
  • Esophagus
    • This is the tube that runs from the mouth to the stomach
    • Foods are swallowed and a process called peristalsis moves the food and liquid through the gastrointestinal tract 
  • Lower esophageal sphincter
    • At the end of the esophagus is a ring-like muscle that allows food to pass into the stomach
    • This sphincter usually remains closed to prevent the contents of the stomach from flowing back up into the esophagus 
  • Stomach
    • The upper muscle in the stomach relaxes to let food enter, and the lower muscle mixes food with digestive juice
    • Stomach acid and enzymes help break down proteins
    • Stomach muscles mix food with these digestive juices 
    • The contents of the stomach, called chyme, are emptied into the small intestine
  • Small intestine
    • Peristalsis moves food and liquid through the small intestine
    • Digestive fluids and enzymes in the small intestine further break down carbohydrates, proteins, and carbohydrates
    • The walls of the small intestine absorb water with other nutrients from the bloodstream to help break down food
    • While in the small intestine, digestive juices from the pancreas, liver, and gallbladder mix in to aid in digestion
      • The pancreas secretes pancreatic enzymes delivered to the small intestine through ducts to break down carbohydrates, fats, and proteins
      • The liver secretes bile acids via bile ducts that help break down fats and some vitamins
      • The gallbladder stores bile between meals, and after you eat the gallbladder pushes bile through the bile ducts into the small intestine
  • Large intestine (colon)
    • More water moves from the GI tract into the bloodstream
    • Bacteria help break down leftover nutrients and produce vitamin K
    • Waste products from the digestive process such as undigested food, fluids, and older cells lining the digestive tract are changed from liquid into the stool
    • Peristalsis helps move stool into the rectum
  • Rectum
    • The end of the large intestine
    • The stool is stored until it is pushed out of the anus during a bowel movement 

How Long Does It Take to Digest Food?

The time it takes to digest food can vary among individuals, but on average it takes: 

It takes between 10 to 73 hours for food to transit from the mouth all the way through the digestive system to be excreted from the large intestine:

  • Two to five hours for food to pass through the stomach after eating
  • Two to six hours to transit through the small intestine
  • 10 to 59 hours to transit through the colon

There are certain factors that can affect transit time through the digestive system as well. 

  • Gender
    • It can take up to 14 hours longer for food to move through a female’s digestive tract than a male’s 
    • Females have a longer colon than males, their colon must share space with the bladder and multiple reproductive organs, and hormonal changes can impact gastrointestinal function in females
  • Age
    • Bodily functions slow as we age, including digestion, so older people digest food more slowly than younger people 
  • Diet 
    • Fruits and vegetables and other foods high in insoluble fiber pass through the digestive system more quickly
    • Meats can take up to two to three days to pass through the digestive system
    • Foods high in soluble fiber, such as those found in barley, oats, root vegetables, and chia seeds can slow digestion
  • Metabolism
    • Those with a higher metabolism have faster digestive transit time while a slow metabolism means slower digestion time
  • Exercise
    • Exercise improves blood flow to the muscles of the digestive system, which helps food transit faster
  • Medical conditions that can slow digestion
    • Functional disorders like irritable bowel disease (IBS)
    • Thyroid dysfunction 
    • Metabolic disorders such as diabetes


Pancreatitis is inflammation of an organ in the abdomen called the pancreas. See Answer

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Reviewed on 7/18/2022

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